Ube “ Westmtnst er ” Series. 
 
 INDIA-RUBBER AND ITS 
 MANUFACTURE. 
 
INDIA-RUBBER 
 
 AND ITS MANUFACTURE 
 
 WITH CHAPTERS ON GUTTA-PERCHA 
 AND BALATA 
 
 BY- 
 
 HUBERT L. TERRY, F.I.C., 
 
 Assoc. Inst. MM. 
 
 NEW YORK 
 
 D. VAN NOSTRAND COMPANY 
 
 23 MURRAY AND 27 WARREN STREETS 
 1912 
 
CjjfOS, 
 
 T 5 
 
 I Wo 
 rs 
 
 THE GETTY CENTER 
 LIBRARY 
 
PREFACE. 
 
 The largely-extended use in recent years of india-rubber 
 tyres on vehicles of all sorts has led to an increased interest 
 being taken by the general public in the natural history and 
 manufacture of rubber. Moreover, the establishment within 
 the last year or two of numerous rubber plantations in 
 Ceylon, the Straits Settlements, and Malaya has led to 
 this almost indispensable commodity becoming a common 
 topic of conversation. 
 
 The present volume, therefore, which is expressly 
 designed for the general reader and for the technologist 
 in other branches of industry, cannot be considered a 
 superfluity—that is, if its scheme of bringing information 
 up to date is considered by the critical reader to have been 
 accomplished. It may be as well to state emphatically that 
 this small volume does not pose as a working guide or 
 hand-book for the india-rubber manufacturer, though it is 
 hoped that the latter may find something to interest him in 
 its pages. Success in the manufacture of india-rubber goods, 
 I am well aware, depends largely upon close observance of 
 detail. Except to the somewhat limited circle of manu¬ 
 facturers such points of detail have no interest or signifi¬ 
 cance, and I have therefore avoided digressing into them 
 or attempting to shed light on the numerous problems in 
 the manufacture which, despite the energies of an increasing 
 body of investigators, still await solution. Naturally, I 
 
VI 
 
 PREFACE. 
 
 have had frequent occasion to refer to the works of pre¬ 
 vious authors, and I wish to express my indebtedness to 
 Messieurs E. Chapel and G. Lamy-Torrilhon, of Paris, 
 Herr F. Clouth, of Cologne, and Mr. H. C. Pearson, of 
 New York, as well as to the publishers of Dr. Weber’s book, 
 bo the Editors of the India-rubber World and the India- 
 rubber Journal I am particularly indebted, as it would be a 
 vain task lo attempt to bring the subject up to date without 
 frequent reference to the files of these journals. A certain 
 amount of the subject-matter has appeared during the last 
 ten years or so in the form of articles in the technical 
 Press. In every case the article has been entirely 
 re-written, but I have to acknowledge the courtesy of 
 the Editors of the India-rubber World, the India-rubber 
 Journal, The Engineer, Engineering, The Electrician, and 
 the Electrical Review, for their permission to republish. 
 
 With respect to the subject-matter, my best thanks are ten¬ 
 dered to Colonel R. K. Birley, C.B., Y.D., for reading through 
 the manuscript, and to Mr. A. E. Walker for much informa¬ 
 tion regarding raw rubber. For the botanical illustrations 
 I am indebted to the pen of Mr. H. F. I. Incledon-Webber, 
 except in the case of Fig. 1, which is from a photo given me 
 by Mr. C. B. Cowper-Coles. Figs. 2, 4, and 5 have been 
 reproduced from the Indiarubber World by the kind per¬ 
 mission of the Editor. For the machinery cuts I have to 
 express my obligations to Mr. J. Iddon, M.I.Mech.E. 
 
 Laboratory, 
 
 23, Hopwood Avenue, 
 Manchester. 
 
 THE AUTHOR, 
 
CONTENTS 
 
 ° HA '' PAGE 
 
 PREFACE ....... y 
 
 I. INTRODUCTION : HISTORICAL AND GENERAL . . 1 
 
 IT. RAW RUBBER—BOTANICAL ORIGIN-TAPPING THE 
 
 TREES - COAGULATION - PRINCIPAL RAW 
 
 RUBBERS OF COMMERCE — PSEUDO RUBBERS- 
 
 CONGO RUBBER—GENERAL CONSIDERATIONS . 13 
 
 III. CHEMICAL AND PHYSICAL PROPERTIES . . 64 
 
 IV. VULCANIZATION ...... 82 
 
 V. INDIA-RUBBER PLANTATIONS .... 95 
 
 VI. INDIA-RUBBER SUBSTITUTES .... 104 
 
 VII. RECLAIMED RUBBER . . . . . .115 
 
 VIII. WASHING AND DRYING OF RAW RUBBER . . 127 
 
 IX. COMPOUNDING OF RUBBER . . . .135 
 
 X. RUBBER SOLVENTS AND THEIR RECOVERY . . 150 
 
 XI. RUBBER SOLUTION ..... 157 
 
 XII. FINE CUT SHEET AND ARTICLES MADE THEREFROM 161 
 
 XIII. ELASTIC THREAD ..... 171 
 
 XIV. MECHANICAL RUBBER GOODS . . 177 
 
 XV. SUNDRY RUBBER ARTICLES . . . .198 
 
 XVI. INDIA-RUBBER PROOFED TEXTURES . . . 213 
 
 XVII. TYRES. -226 
 
CONTENTS. 
 
 viii 
 
 CHAP. 
 
 XVIII. 
 
 INDIA-RUBBER BOOTS AND SHOES 
 
 
 PAGE 
 
 . 239 
 
 XIX. 
 
 RUBBER FOR INSULATED WIRES 
 
 
 . 243 
 
 XX. 
 
 VULCANITE ..... 
 
 
 . 249 
 
 XXI. 
 
 CONTRACTS FOR INDIA-RUBBER GOODS 
 
 
 . 255 
 
 XXII. 
 
 THE TESTING OF RUBBER GOODS 
 
 
 . 261 
 
 XXIII. 
 
 GUTTA-PERCHA ..... 
 
 
 . 271 
 
 XXIV. 
 
 BALATA ...... 
 
 
 . 281 
 
 BIBLIOGRAPHY 
 INDEX . 
 
 289 
 
 291 
 
ILLUSTRATIONS. 
 
 FIG. PAGE 
 
 1. CASTILLOA ELASTICA. LAS CASCADAS PLANTATION, 
 
 PANAMA ....... 3 
 
 2. TAPPING LANDOLPHIA VINES IN THE CONGO REGION 15 
 
 3. HEVEA BRAZILIENSIS ...... 17 
 
 4. SMOKING PARA RUBBER WITH PALM NUTS BY THE 
 
 PADDLE METHOD ...... 21 
 
 5. SMOKING PARA RUBBER WITH PALM NUTS BY THE 
 
 ' METHOD WHICH HAS RECENTLY SUPERSEDED 
 THE PADDLE TO A GREAT EXTENT . . . 25 
 
 6. CASTILLOA ELASTICA . * . . . .35 
 
 7. FICUS ELASTICA ....... 43 
 
 8. LANDOLPHIA OWARIENSIS ..... 49' 
 
 9. CARPODINUS LANCEOLATUS (AFRICAN ROOT RUBBER) 61 
 
 10. WASHING ROLLS ....... 129 
 
 11. MIXING ROLLS ....... 180’ 
 
 12. DIAGRAM OF THREE-BOWL CALENDER . . . 182 
 
 13. FOUR-BOWL CALENDER. . . . . .188 
 
 14. BELTING VULCAN PRESS ..... 188 
 
 15. SIX PLATEN HYDRAULIC VULCAN PRESS . . . 190 
 
 16. SPREADING MACHINE ...... 215 
 
 17. CAB TYRE FORCING MACHINE .... 228 
 
 18. SECTION THROUGH IRON MOULD SHOWING PNEU¬ 
 
 MATIC MOTOR TYRE DURING VULCANIZATION . 235 
 
 I.R. b 
 

INDIA-RUBBER 
 
 CHAPTER I. 
 
 INTRODUCTION : HISTORICAL AND GENERAL. 
 
 n India-rubber, or caoutchouc, is the name commonly given 
 to the milky latex occurring in the bark of certain species 
 of trees. The latter term is variously derived by authors 
 from the vocabularies of South-American Indians, but it is 
 not proposed to say anything here on the point. In this 
 work the common English name of “india-rubber,” or, more 
 shortly, “ rubber,” will alone be employed, though having 
 regard to the multifarious uses to which the substance is now 
 put, this old name, which bears reference to its original 
 use, cannot be considered an ideal one. In America and 
 on the Continent the term “gum,” or its foreign equivalent, 
 is commonly used—a practice which has little to recom¬ 
 mend it, and, indeed, is decidedly objectionable as tending 
 to confusion with the real gums which are soluble in cold 
 water. Still, the American “gum,” the German “gummi,” 
 the French “ gomme elastique,” the Italian “ gomma 
 elastica,” and the Spanish “goma elastica,” bear testimony 
 to the extent of its adoption. 
 
 With regard to the history of its introduction into 
 Europe, the little that is known with certainty has been 
 
 I.R. 
 
 B 
 
2 
 
 INDIA-RUBBER. 
 
 said so often, and allows such small scope for elaboration, 
 that merely a few words will be sufficient. Two or three 
 Spanish authors in the sixteenth and seventeenth centuries 
 referred to games played by the natives of South America 
 and Mexico with an elastic ball obtained from the white 
 exudations of certain trees. It was reserved, however, for 
 the French travellers, De la Condamine and Fresnau, to 
 make known to the scientists of Europe the nature of the 
 substance and the various uses to which they found it 
 applied. This was during the years 1781—1736, and it 
 was soon after experimented upon by French chemists, and 
 also by the English chemist, Priestley, who is credited 
 with the proposal to use it for effacing pencil marks. In 
 1791, Samuel Peal took out a patent for waterproofing 
 cloth by brushing the hot rubber on it, and in 1818 
 John Clark dissolved rubber in turpentine and applied the 
 solution to the manufacture of air beds. 
 
 It was not, however, until 1820, when Charles Macin¬ 
 tosh, F.E.S., of Glasgow, proposed the use of a solution of 
 india-rubber in coal-tar naphtha for the manufacture of 
 waterproof garments, that the substance became important 
 as the raw material for an industry. Macintosh entered 
 into partnership with the Messrs. Birley, of Manchester, 
 and the year 1823 witnessed the foundation of the pioneer 
 firm of Messrs. Charles Macintosh and Co. in an industry 
 which was destined to have such great developments in 
 succeeding years. This firm is still in the forefront of the 
 trade, and although numerous extensions have been made 
 to the premises, the original building in which the first 
 rubber-spreading machinery was erected is still being 
 utilised for the same class of work. With regard to 
 
INTRODUCTION: HISTORICAL AND GENERAL 
 
 3 
 
4 
 
 INDIA-RUBBER. 
 
 actual priority of manufacture, there is very little between 
 Charles Macintosh and Thomas Hancock. The latter was 
 in the year 1819 energetically pursuing investigations on 
 india-rubber, and if it had occurred to him to use naphtha 
 instead of turpentine, a well-known article of clothing 
 would doubtless have received some other name than that 
 by which it is so universally known. In other respects, 
 however, in its influence upon the development of the 
 trade, Hancock’s work as regards the mastication and 
 vulcanization of india-rubber was of far greater importance 
 than was Macintosh’s, and a business arrangement was 
 formed in 1826 between Hancock and the Macintosh firm 
 at Manchester for their mutual advantage. The former’s 
 original factory in Goswell Road, London, is still carried 
 on by his descendants, and can legitimately be called the 
 oldest factory in the trade, though, as far as vulcanized 
 rubber is concerned, that distinction belongs indisputably 
 to Charles Macintosh and Co. Those who would know more 
 of Hancock and his work will find it fully treated in his 
 “ Personal Narrative of the Origin and Progress of the 
 India-rubber Manufacture in England,” published in 1857. 
 It indicates the indomitable perseverance with which he 
 applied himself to the solution of baffling problems, though 
 naturally in the advanced knowledge of these later times 
 it is not always easy to appreciate the disabilities under 
 which the forerunners in this industry laboured, or to make 
 due allowance for their failure to grasp the significance of 
 what we have come to look upon as obvious. The book 
 has, of course, been long out of print, and many will, 
 therefore, probably find it difficult of access. Hancock’s 
 first important discovery was that scraps of pure rubber 
 
INTRODUCTION: HISTORICAL AND GENERAL. 
 
 5 
 
 could be made into a solid block by mechanical action. 
 In this form the rubber could be cut into sheets, and it was 
 at once recognised that the discovery would have an im¬ 
 portant bearing upon its applications. The “ masticator,” or 
 “ pickle,” by which latter name Hancock called the machine 
 he had invented, only produced blocks of a few inches in 
 length and breadth, but in principle, as we shall see in a 
 later chapter, it has undergone very little change in the 
 course of its existence, except in increased dimensions and 
 capacity. No patent was taken out by Hancock for his 
 machine, and it was kept a secret for twelve or thirteen 
 years until a workman divulged its details. Having 
 obtained a licence from Macintosh to work his patent, 
 Hancock soon found that in his masticated rubber he had 
 an advantage over the Manchester firm, as he could make a 
 much stronger solution with the same quantity of naphtha. 
 It was this fact which led to the business arrangement 
 already notified as having been entered into in 1826 
 between Hancock and the Macintosh Company at Man¬ 
 chester. During the next twenty years, although business 
 proceeded steadily, no particularly rapid progress was made 
 in applying rubber to the needs of the arts and manu¬ 
 factures. This was due to the fact that it was affected so 
 largely by heat and cold, and it was not until after 1844, 
 when the discovery of vulcanization had been made, that 
 the manufacture showed any considerable expansion. It 
 is impossible to exaggerate the importance of the vulcaniza¬ 
 tion process; without it, it is clear that the industry of 
 to-day, subserving as it does so many of the needs and 
 fancies of mankind, could never have attained to its 
 imposing dimensions. 
 
6 
 
 INDIA-RUBBER, 
 
 Since 1845, although the new applications of vulcanized 
 rubber have been numerous enough, there has been no 
 discovery of any revolutionary character in connection with 
 the manufacture, progress having been pretty generally 
 confined to improvements in the processes and plant of 
 sixty years ago. A momentous advance has been made, 
 however, in the way of reducing the amount of rubber in 
 some classes of goods to a negligible quantity, hut this sort 
 of progress has very dubious claims to consideration. It 
 has been contended that for the last fifty years there has 
 been no discovery of a revolutionary character as far as the 
 manufacture is concerned. Exception may he taken to 
 this dictum by those chemists who have credited Mr. 
 Kelway Bamber with having inaugurated a new era. Mr. 
 Bamber has recently proposed to vulcanize the coagulated 
 rubber in the precincts of the plantation or forest with 
 chloride of sulphur in order to prevent the fermentation of 
 albuminous matters during transit to Europe, hut the nip¬ 
 ping in the bud here proposed is likely to create fresh evils 
 of greater potency than those it is sought to eradicate. 
 Perusal of the following pages will make it abundantly clear 
 that rubber goods are made in a variety of ways, and in the 
 majority of cases from a mixture of materials; moreover, 
 the vulcanization is always one of the final processes in the 
 manufacture, and it is difficult to see the value of the 
 proposal. 
 
 As already stated, the French scientists were the first to 
 make the substance and its properties known in Europe, 
 hut the credit of establishing the rubber manufacturing 
 industry belongs to Great Britain, though it was not many 
 years after the commencement that works were started in 
 
INTRODUCTION: HISTORICAL AND GENERAL. 7 
 
 France, Germany and America. At the present time, in 
 addition to these countries, we find factories in Austria- 
 Hungary, Italy, Holland, Russia, Denmark, Norway, Sweden, 
 Belgium, Switzerland, and Portugal, as well as in Australia 
 and Japan. The term “india-rubber works” is, however, a 
 very comprehensive one, some of the concerns being quite 
 small ones, limited both in their output and as to the nature of 
 the goods they manufacture ; others of imposing dimensions 
 are occupied almost entirely in one class of production, for 
 instance, goloshes; while others, again, may turn out practi¬ 
 cally all the rubber goods which have so far been introduced. 
 The qualifying term “practically” is used of set purpose, 
 because the author is not aware of any factory where rubber 
 goods of all kinds are manufactured. There are large 
 concerns in existence where the omissions are extremely 
 few in number, and these may be attributed either to want 
 of room for the necessary work, or to a feeling that the 
 branch does not offer sufficient pecuniary profit for the risk 
 of the capital. In one or two branches specialisation may 
 be attributed largely to the fact that the details of the 
 processes involved are by no means generally known, and 
 that skilled supervision and labour would be with difficulty 
 obtained by new firms wishful of competing with old-estab¬ 
 lished ones in some special branch of the trade. For 
 example, until comparatively recent times, two or three 
 large English works supplied the requirements of the world 
 as regards fine-cut sheet and elastic thread, and their status 
 in the markets still remains. From America, France, Italy 
 and Germany, however, competition has now to he met, 
 with the consequence of diminished profits. The tendency 
 in the large European works has been to make all sorts of 
 
8 
 
 INDIA-RUBBER. 
 
 goods, while in America specialisation in particular branches 
 has been the general rule. The advantages of specialisa¬ 
 tion in the way of getting out quantity at a minimum 
 expense are well known; its disadvantage lies in the fact 
 that any decreased demand may rapidly bring about 
 financial trouble. Where a factory makes all classes of 
 goods a falling off in the demand for any one of them does 
 not make itself so severely felt. In this respect, on looking 
 back into history, we have to note the great falling off in 
 the demand for elastic thread for shoe elastic; the manu¬ 
 facturers, however, soon found expansion in other depart¬ 
 ments to make up the loss of trade. In quite recent times 
 we have witnessed the decline of the macintosh as a 
 popular article of apparel. As a number of firms were 
 engaged in this branch only, it is not surprising that several 
 have entirely closed their works. The plant and machinery 
 did not permit of their being put to other purposes, and 
 taking up an altogether new branch, such as the manufac¬ 
 ture of pneumatic tyres, meant the employment of a much 
 larger capital. 
 
 If one can correctly gauge the pulse of the trade the 
 tendency of the near future will be to close existing works 
 rather than open new ones. The volume of trade has of 
 course increased, but it is the general complaint that too 
 much competition exists, and this not only in Great Britain, 
 but in leading Continental countries. Despite the great 
 access of business resulting from the increase of motor 
 vehicles, existing factories have managed to cope with it, 
 with or without extension of premises. Germany, alone, 
 has about sixty india-rubber factories, many of the leading 
 firms of the Fatherland, as well as those of other countries, 
 
INTRODUCTION: HISTORICAL AND GENERAL. 
 
 9 
 
 halving offices and agents in London. With the advent of 
 neiw countries into the manufacturing arena the foreign 
 miarket for the older-established ones becomes more and 
 nnore restricted, a specific instance of this being the large 
 decline of German exports to Scandinavia since Norway 
 amd Sweden started their own rubber factories a few years 
 ag'O. That the manufacture has advanced beyond require¬ 
 ments in Austria is testified to by the recent formation of 
 a manufacturers’ union, one of the objects of which was 
 the concentration of certain classes of work in particular 
 factories. The fact that with the great rise in the price of 
 tine raw material there has been a steady increase in the 
 vodume of the business done in manufactured goods is 
 ekoquent testimony to the recognition of rubber as a 
 necessity rather than a luxury. Nor must this increased 
 demiand be considered to have emanated from one source 
 ondy. There is a tendency to give the motor tyre the sole 
 credit for the recent expansion in the rubber industry. 
 Tdhis article perhaps comes more before the public eye than 
 is the case with many others; but though, of course, the 
 tyre is responsible for much of the increased business, a 
 g r ’eat deal of rubber goes nowadays to places where it is 
 comcealed from the public vision. For instance, in a 
 modern man-of-war, besides the engine valves and washers, 
 thiere is the large number of armour plate bolt washers, the 
 U&e of which is enjoined by modern practice. To these must 
 be added stair treads and mats and various other articles 
 wlhicli come from the mechanical goods department of the 
 ruibber works. Then the electric cable industry must not be 
 overlooked; but not to follow this topic further, it will 
 suiffice to say that the increase in the demand is a very 
 
10 
 
 INDIA-RUBBER. 
 
 general one from a variety of sources, and this under the 
 prevailing conditions of price must be taken as a good 
 augury for trade prospects for some years to come at any 
 rate. 
 
 A word as to the mechanical power used in rubber 
 factories may not he without interest. Although the great 
 bulk of the factories employ steam power, this has been 
 replaced in recent years by electrical power in several 
 cases, and with very satisfactory results. As far as Great 
 Britain is concerned, this innovation is only to be found 
 in two or three factories, of which that of the Leyland and 
 Birmingham Company invites special mention. The 
 current was installed in 1888. Besides the heavy rubber 
 machinery, many of the smaller machines are run by 
 motors fixed in the various workrooms. Electric power 
 has also been used for many years in the rubber depart¬ 
 ment of Messrs. Siemens’ cable works at Woolwich, and is 
 now installed at the works of the Avon Rubber Company at 
 Melksham, and at the St. Helens Cable and Rubber Com¬ 
 pany of Warrington. Of Continental firms using this 
 source of energy, the large factory of Pirelli et Cie at 
 Milan may be mentioned. And in America electrical driving 
 is employed in the new factory of the United States Rubber 
 Reclaiming Company at Buffalo, the current being obtained 
 from Niagara Falls. As electrical power has such an 
 advantage over steam in the ease and economy with which 
 its transmission in the factory is effected, we may expect to 
 see it more largely adopted in the future. Water power as 
 the direct source of energy is not unknown in the rubber 
 factory. In France, at the works of Torrilhon et Cie., at 
 Clermont Ferrand, the washing plant, which is situated at 
 
INTRODUCTION: HISTORICAL AND GENERAL. 
 
 11 
 
 a short distance from the main factory, is driven by a 
 water-wheel. This is a special instance where local 
 conditions are advantageous, but in a general way water 
 power cannot be considered as suitable for a rubber factory, 
 because of the great variations in the power required for 
 different brands of rubber on the mixing rolls. The steam 
 turbine of the De Laval type has been advocated by 
 American engineers as suitable for rubber factory driving, 
 but details of any installation are not yet to hand. 
 
 Hygiene in the Rubber Factory .—Reference is made else¬ 
 where to poisoning by carbon bisulphide, and if we leave 
 this body out of account there is really nothing in the 
 manufacture that can be considered particularly injurious. 
 
 With regard to naphtha fumes, there is rather conflicting 
 evidence. As far as the spreading machines are concerned, 
 nothing serious can be urged against the naphtha vapours ; 
 where they are too dense the workman who gets too strong 
 a dose rapidly removes himself to a distance, and the 
 danger of fire from concentration of the vapours has led in 
 the majority of cases to efficient ventilation being provided. 
 In the case of large numbers of girls working with rubber 
 solution in a warm and badly-ventilated room in the 
 making up of macintosh garments or pneumatic tyres, 
 there have been several instances of light-headedness or 
 even stupefaction occurring. No doubt in the majority of 
 cases efficient ventilation would have obviated this, but 
 idiosyncrasy in the individual worker is a factor which must 
 not be overlooked. An amount of vapour which will work 
 havoc on one constitution will leave another practically 
 unaffected, and for work of this sort it must not be assumed 
 that all hands are equally suited either in their own 
 
12 
 
 INDIA-RUBBER. 
 
 interests or in that of their employers. A judicious 
 weeding out of the constitutionally unfit is desirable in such 
 cases. Dismissal need not necessarily follow if this sugges¬ 
 tion were adopted; it would merely mean transference 
 from one department to another. It can hardly be a 
 matter for contention that the more healthy the surround¬ 
 ings of the factory the more chance the workers have of 
 combating any dangers to health which may arise from the 
 incidence of their employment, and therefore it is advisable 
 to take into consideration not only heredity in individuals, 
 but also environment, before generalising upon the 
 healthiness or otherwise of the rubber trade. 
 
CHAPTER II. 
 
 PRODUCTION OF RAW INDIA-RUBBER. 
 
 All the trees which produce india-rubber of economic 
 importance are found growing in the inter-tropical area 
 comprised within a distance which may be roughly put at 
 250 miles both north and south of the equator. The 
 climate is, generally speaking, warm and moist, and the 
 rainfall, though varying considerably according to locality, 
 averages about 80 inches a year. Outside this region many 
 plants have been described which contain a milky juice not 
 unlike india-rubber latex in appearance, but despite various 
 attempts which have been made to utilize them, no success 
 has been attained, and they need not be further considered 
 here. 
 
 The rubber plants growing in the equatorial belt belong 
 to different botanical orders, which are shown in the 
 annexed table, together with some of the more important 
 species from which the different raw rubbers of commerce 
 are obtained. 
 
 Recent botanical research has added largely to the 
 number of species yielding marketable rubber, and has 
 also done a good deal to clear up the confusion which only 
 a few years ago was so apparent on the subject, more 
 especially in regard to African brands. The topic can only 
 be dealt with cursorily in these pages owing to limitation of 
 
14 
 
 INDIA-RUBBER. 
 
 space, and those who are wishful of gaining fuller insight 
 must consult the manuals on botany. Much information 
 has also been collected by Seeligmann, 1 Franz Clouth 2 and 
 Chapel, 3 in whose hooks the existing situation up to a few 
 years ago is ably summarised. Among the alterations in 
 nomenclature, attention may be called to the fact that the 
 
 Natural Order. 
 
 Genus. 
 
 Species. 
 
 Locality. 
 
 Et/PHORBIACEjE . 
 
 Hevea . 
 
 //. Brazil.ie.nsis . 
 
 Amazon, Orinoco. 
 
 
 Manihot 
 
 M. (jlaziovii 
 
 Ceara. 
 
 Artocarpaceje . 
 
 Micranda 
 
 M. major . 
 
 Amazon. 
 
 Castilloa 
 
 (i. elastica 
 
 Central America. 
 
 Apocynaceas 
 
 Ficus 
 
 F. elastica 
 
 F. Voi/elii 
 
 F. various 
 
 Assam, Rangoon, 
 Java. 
 
 Gold Coast. 
 Soudan, Vene¬ 
 zuela. 
 
 Rancor uia 
 
 //. speciosa 
 
 Pernambuco, 
 
 Peru. 
 
 
 Urceola . 
 Funtumia 
 
 U. elastica 
 
 F. elastica 
 
 Borneo. 
 
 
 {Kicksia 
 
 K. Africana ] 
 
 Central Africa. 
 West Africa. 
 Congo region. 
 
 Asclepiadete . 
 
 L an do Ip ilia . 
 
 Large number . 
 
 Madagascar. 
 
 Mozambique. 
 
 Callotropis 
 
 C. yigantea 
 
 Assam. 
 
 Kicksia elastica of West and Central Africa is now known as 
 the Funtmnia elastica. Of the trees mentioned in the table, 
 one, the Ficus elastica, will be well-known to many as the 
 familiar liot-house plant. It is but rarely to be met with in 
 Europe of the size it attains in East Indian districts, and 
 
 1 “India-rubber Manufacture,” by Seeligmann, Torrilhon, and 
 Falconnet. 
 
 2 “India-rubber, Gutta-percba, and Balata.” 
 
 8 “Le Caoutchouc et la Gutta-percha.” 
 
16 
 
 INDIA-RUBBER. 
 
 it is hardly necessary to say that, as found in England, it is 
 ornamental rather than useful. 
 
 India-rubber trees show great variations in form and size. 
 While the Hevea of the Amazon swamps often attains a 
 height of 120 feet and the Hancornia of 50 feet, the bulk 
 of the Landolphias of W r est Africa are merely of the creeper 
 or liane kind, depending for their support upon other trees 
 of the forest. The greatest insignificance, however, is 
 found in the shrubs from which the root rubber of the 
 Congo State is obtained. These plants have no climbing 
 powers, merely growing from 1 to 2 feet high above the 
 sand. It was with these plants, of which the Carpodinus 
 lanceolatus and the Clitandra species may be mentioned, 
 that the somewhat sensational paragraphs which went the 
 round of the daily papers two or three years ago were 
 concerned. Wonderful visions were conjured up of the 
 new source of wealth that had been discovered, though, as 
 a matter of fact, the discovery by the papers was somewhat 
 belated, rubber from this source having been exported from 
 the Congo regions for many years in greater or less quan¬ 
 tities. This rubber is obtained, it should be mentioned, 
 from the rhizomes or underground stems. 
 
 Tapping the Trees .—The latex or india-rubber milk must 
 not be confused with the regular sap of the tree. Scientists 
 are not yet agreed as to the particular function played by 
 this peculiar secretive body, but it seems to have been 
 satisfactorily proved that, although necessary to the life of 
 the plant up to a certain age, after that time it is no longer 
 so. It will be sufficient to state that after the tree has 
 attained to a certain growth it can be tapped without 
 injury at intervals of time. Generally speaking, young 
 
PEODUCTION OF RAW INDIA-RUBBER. 
 
 17 
 
 trees should be six or seven years old before they are 
 tapped, and an interval of a year should elapse between a 
 series of tappings. 1 There can be little doubt that prema¬ 
 ture tapping injures the trees, and gives, moreover, an 
 inferior product to that extracted from old trees. The 
 
 FIG. 3.—HEVEA BRA/.ILIENSIS. 
 
 exact life of a rubber tree is probably not known, but it is 
 within the knowledge of old South American collectors that 
 Para trees have been yielding rubber for at least fifty years. 
 
 1 The latest idea amongst rubber planters is that after the tree has 
 grown old enough to bear tapping, it can be tapped at very frequent 
 intervals with advantage to the yield of latex, provided the tree is not 
 at any tune bled to excess. 
 
 I.R. 
 
 C 
 
18 
 
 INDIA-EUBB EE. 
 
 The rubber latex is secreted in the intercellular veins 
 which are found in the interior of the bark, and though in 
 close proximity to the sap veins, they are quite distinct 
 from them. For further details of scientific interest 
 botanical works must be consulted. Of especial importance 
 are Morellet’s contributions to the subject. 
 
 There are two methods followed in obtaining the rubber 
 latex, the first or rational one being by making incisions in 
 the bark and collecting the fluid as it exudes, and the 
 second or barbarous method that of cutting down the tree. 
 In the first case, the collector, though desirous of getting as 
 much rubber as he can, works with an eye to the future, 
 while the advantage of the moment is all that enters into 
 the consideration of the rubber gatherer in the second case. 
 In order that full justice shall be done, it ought to be said 
 that all the rubber-producing trees do not lend themselves 
 equally to the tapping process, nor are the conditions of 
 labour identical, for instance, in West Africa and the 
 Amazon region. All the same, it will be generally conceded 
 that the destruction of trees has in the past been carried to 
 a quite unnecessary extent, and that a course of procedure, 
 which is on the face of it irrational, calls, at any rate, for 
 careful consideration, if not for universal condemnation. 
 Human nature being what it is the world over, it is perhaps 
 too much to expect that the untutored collector in little- 
 explored districts will take much thought for the morrow if 
 he himself has little chance of deriving benefit from the 
 result of his forethought. “ It is all very well,” we can 
 imagine him saying, “for companies who own their own 
 collecting areas to safeguard the interests of the future; 
 their position is such that they can afford to bide their 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 19 
 
 time.” It is pretty clear, therefore, that the native collector, 
 unless under Government supervision, will continue to cut 
 down rather than tap the trees. The reason given for 
 felling the caucho trees in Peru is that the latex will not 
 flow from the upright trunk, also that the tree occurs in 
 such superabundance that any failure of supply is to be 
 considered an exceedingly remote eventuality. This may 
 or may not be the case as regards the latter contention, but 
 if the former statement is not exaggerated it certainly 
 seems to be a matter calling for the attention of experts. 
 There is no doubt that the caucho tree has been exhausted 
 in many districts for the time being, the attention of the 
 collectors being now transferred to what is known as Jebe 
 rubber, a product of the TIevea guayanensis, until a new 
 generation of caucho trees arrive at maturity. 
 
 The actual process of tapping the Para rubber tree has been 
 so often described, and in considerable detail, that one hesitates 
 to occupy space with matter which is presumably pretty well 
 known. In order, however, to ensure completeness in the 
 treatment of the subject, a condensed account is appended. 
 
 The work is carried out by “ seringueros,” natives who are 
 acclimatised to the miasmatic swamps in which the bulk of 
 the work is carried on. Their number is nowadays largely 
 augmented by learners, who engage themselves during the 
 collecting season to work for the rubber merchants in Para 
 and Manaos, by whom they are supplied with the necessary 
 equipment. Good native labour is by no means superabun¬ 
 dant, this being due not only to lack of population, but 
 also to the claims of coffee planters for labour. Moreover, 
 the mortality among even the acclimatised collectors is 
 sufficiently alarming to act as a deterrent to recruits when 
 
 c 2 
 
20 
 
 INDIA-RUBBER. 
 
 labour under more hygienic conditions can be obtained. 
 However, to follow the collectors to their work. On arrival at 
 a suitable tree, they proceed to make incisions in the bark 
 with a small axe, called the “ machado,” which does not 
 damage the tree, as the instruments formerly employed used 
 to do. The incisions take various forms, sometimes being 
 merely vertical cuts; at other times they take a V-sliape, or 
 they may be in curves. Undereach of the cuts the collector 
 fixes a small tin cup by means of moist clay, and in this cup 
 the latex slowly collects. Those who have travelled through 
 the Landes from Bordeaux to the Spanish frontier, or on 
 the line from Burgos to Madrid, will no doubt have seen the 
 collecting of turpentine from the sea-pine by means of tin 
 cups affixed to the stems of the trees, the effect in a general 
 way being similar to that seen in the case of Para rubber. 
 
 Although the rubber may be collected at any time of the 
 year, the best yield is obtained from the beginning of Sep¬ 
 tember to the beginning of February, and the work is 
 usually carried out at this season, which is the period of 
 greatest rainfall. On an average half a pound of rubber is 
 obtained from each tree, not at all a large amount when we 
 compare the yield which is being obtained from cultivated 
 sources. It is probable that the future will see develop¬ 
 ments in the methods of tapping the trees adopted in South 
 America on the lines which careful study on the Ceylon 
 plantations has shown to be advantageous. At the same 
 time we must remember that the Ceylon planters are only 
 feeling their way, while the Brazilian collector has the 
 experience of his forefathers to guide his actions. 
 
 Having obtained a quantity of the rubber latex, the col¬ 
 lector proceeds to coagulate it in the following manner :— 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 21 
 
 In a ruclely-constructed oven, called the “fumeiro,” having 
 a cone-shaped top, a fire of faggots is made and kept going by 
 
 FIG. 4.—SMOKING PARA RUBBER WITH PALM NUTS BY THE PADDLE 
 
 METHOD. 
 
 the addition of palm nuts (Attalea excelsa). When a sufficient 
 amount of smoke is being evolved the collector takes a sort 
 
22 
 
 INDIA-RUBBER. 
 
 of wooden paddle 1 4 or 5 feet long, dips it in the latex, 
 and turns it over in the smoke, when the water evaporates, 
 leaving a thin layer of india-rubber. This process is con¬ 
 tinually repeated until a “ biscuit ” of ten or eleven pounds 
 weight is formed, and this, after being removed from the 
 paddle by a knife cut, is ready for transport to the trading 
 centres. It is understood that the use of the particular 
 nuts mentioned above is almost confined to the lower 
 Amazon, wood alone being used in the upper regions. 
 Whether these nuts have any very special properties 
 beyond what are to be found in the ordinary timber of the 
 forest does not seem to have been definitely proved, and at 
 any rate the difference, if any, between the products of the 
 nut and the wood smoking is so small that it need not be 
 considered here. The main point is that this smoking 
 process, which is confined to South America, yields the best 
 rubber in the world. This is due, no doubt, to the inter¬ 
 action of several causes, of which the original strength of 
 the rubber latex is a prominent one. There can also he 
 little doubt that the smoking has a beneficial action in 
 arresting any tendency to fermentation on the part of the 
 albuminous matter present. Wood smoke, of course, con¬ 
 tains antiseptic matters which may be lumped under the title 
 creosote, a body which is well known as a preservative 
 agent. The amount of moisture in wood and also the large 
 percentage of oxygen contained is conducive to the formation 
 of bodies like creosote and acetic acid, and it seems quite 
 sufficient to ascribe the antiseptic properties of the smoke to 
 these bodies without suggesting, as Clouth does, that the 
 
 1 The form of this implement so long in nse has recently undergone 
 a change. 
 
PRODUCTION OP RAW INDIA-RUBBER. 
 
 23 
 
 beneficial action may be largely due to free carbon. To 
 judge from the phenomena of charcoal burning as carried 
 out in forest regions, the production of free carbon in the 
 smoke we are considering seems very doubtful, or at any 
 rate, if it is produced the quantity would appear to be so 
 small that its beneficial action must be largely exceeded by 
 that of the creosote, which gives to the Para rubber its 
 well-known and characteristic smell. The proneness of the 
 rubber latex to spontaneous coagulation is counteracted by 
 the addition of a small quantity of ammonia when it has to be 
 carried any distance from the trees to the place of treatment. 
 
 With regard to the composition of the latex, analyses have 
 been made, showing about 32 per cent, of rubber to be 
 obtainable from it. The following figures were obtained 
 by the author in 1890 from rubber latex sent from Para in 
 bottles, having previously been mixed with some ammonia :— 
 
 Product of the Hevea Braziliensis Para. 
 
 Per cent. 
 
 India-rubber 
 
 . 31-9 
 
 Resins . 
 
 . 1-5 
 
 Albumen . 
 
 . 0*5 
 
 Water and salts . 
 
 . 66*1 
 
 
 100-0 
 
 According to Clouth, the latex of the Ileveas and the 
 Micrandas contains :— 
 
 Per cent. 
 
 Caoutchouc ...... 32 
 
 Organic matters (of decomposing pro¬ 
 perties) . . . . . .12 
 
 Water.56 
 
 100 
 
24 
 
 INDIA-RUBBER. 
 
 with traces of resin. This seems a large proportion of 
 albuminous matters, which were quite small in amount in 
 the above sample. Compared with the amount of work 
 which has been clone in raw rubbers of all kinds, it is some¬ 
 what surprising that so few analyses of the latex have been 
 published. The difficulty of getting the liquid to Europe in 
 an unaltered condition may well account for this in the past, 
 but nowadays, when rubber is being cultivated in the East 
 at no great distance from chemical laboratories this difficulty 
 has lost its imposing dimensions. That the Para latex is of 
 very uniform composition is seen by comparing the figures 
 given above with an analysis made by Faraday many years 
 ago, the oldest analysis on record. These are his figures :— 
 
 Rev cent. 
 
 Caoutchouc . , . . . 
 
 31-70 
 
 Albumen ...... 
 
 1-90 
 
 Other nitrogenous and saline matters . 
 
 10-03 
 
 Water ...... 
 
 5637 
 
 
 100-00 
 
 The second quality of Para rubber, known as entrefine, 
 consists in part of remnants from the cuts in the trees and 
 also of what has coagulated in the cups and in part of 
 smoked rubber, it being customary to dip the pieces of the 
 former into fresh latex and then subject the whole to the 
 smoking process. Though free from dirt, this rubber is 
 naturally, owing to its composite nature, not of the same 
 high quality as that which has been carefully smoked 
 throughout. Various other scraps of the rubber, including 
 a good deal which has fallen on the ground and got mixed 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 25 
 
 with impurities, are made into blocks without going through 
 the smoking process, and are sold as “ Sernamby ” in South 
 America and “ Negroheads ” in the European and United 
 States markets. 
 
 The methods of production elsewhere than in the Amazon 
 
 FIG. 5. —SMOKING PARA RUBBER WITH PALM NUTS BY THE METHOD 
 WHICH HAS RECENTLY SUPERSEDED THE PADDLE TO A GREAT 
 EXTENT. 
 
 district prove that nowhere are the operations carried out 
 with such care and regularity. Various methods of tapping 
 are in use where the trees are not cut down, and coagulation 
 is brought about in a multiplicity of ways, many of which 
 could easily be improved. A Mexican process consists in 
 passing the tapped latex through a sieve into an iron vessel 
 in which it is heated until separation of the rubber on the 
 
26 
 
 INDIA-RUBBER. 
 
 surface takes place. The defect of this process is that the 
 heating is not sufficient to prevent subsequent fermentation. 
 This method is also said to be employed in Assam. In 
 West and Central Africa a common method is for the 
 collectors to smear the latex over their bodies and to peel 
 off the rubber when the water has evaporated. In other 
 districts, especially in the case of the sluggish latex of the 
 Ceara trees, coagulation takes place on the trunk of the tree 
 by natural heat. The solar rays are also the coagulating 
 medium employed in the case of some of the African rubbers, 
 the latex being allowed to flow from the tree on to the 
 ground, a careless proceeding which cannot be commended. 
 Sometimes, also, the latex is mixed with water in variable 
 proportions according to the custom prevailing in the 
 several districts where the system is in operation ; after a 
 time the rubber separates out and rises to the surface. 
 With regard to the coagulation processes used in the Congo 
 region much interesting information has been obtained by 
 Gustave van der Ixerckhove, and an article written by him 
 in the India-rubber World for October, 1904, has been 
 drawn upon in the following remarks. At least six or seven 
 different methods of coagulation are used by natives in the 
 Congo Free State, and as a rule they show so much acumen 
 in choosing the most suitable process for a particular rubber 
 that the advent of civilization has done little but check 
 adulteration. As the Kassai rubber will be referred to later 
 as the best product of the Congo State, it will be of interest 
 to refer to its preparation. In some cases the method, just 
 mentioned as common in Africa, of smearing the latex over 
 the body and allowing it to dry is followed, while in other 
 cases, instead of using the body, the rubber is allowed to 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 27 
 
 coagulate as it exudes from the cuts in the vines and is then 
 wound round the finger or on small sticks. What is known 
 in the market as prime red Kassai is prepared by the latter 
 method, while the prime black Kassai is the product of a 
 boiling and smoking process, the natives apparently having- 
 discovered for themselves the antiseptic properties of smoke 
 without any assistance from those who would be familiar 
 with South American procedure. Another interesting- 
 method of coagulation now largely adopted is the addition 
 of an acid sap called “Bosanga,” obtained from a tree known 
 as the Costus Lucanusianus. On stirring up a small 
 percentage of this juice with the latex coagulation 
 immediately takes place, the resulting mass being shaped 
 into balls and left to dry in the shade or stored in a 
 bungalow. A noteworthy fact about this Bosanga juice is 
 that it only coagulates the latex from vines, that from trees 
 or from the sources of root rubber being unaffected by it. 
 In extracting the root rubber the natives of the Kwango 
 district and around Stanley Pool, where the particular 
 species known as the Landolphin Thollonii is so plentiful, 
 tear up the roots and, having cut them into small pieces, 
 expose them to the sun and afterwards put them into water. 
 The whole is then beaten with sticks to separate the bark. 
 After being dried, the rubber is shaped into sheets half an 
 inch thick, and afterwards cut up into little squares which 
 come into commerce under the name of “thimbles.” A 
 large number of processes depend upon chemicals as their 
 active agent for coagulation, alum, salt, sulphuric acid, 
 citric acid and acetic acid being well known in this 
 connection, while in a Peruvian process for treating the 
 Hancornia, soapy water is the agent employed. 
 
28 
 
 INDIA-RUBBER. 
 
 An interesting coagulation process carried out in Gambia 
 and on the Ivory Coast is a combination of beat with 
 chemical treatment. The collector makes slight cuts in 
 the stem of the creepers and puts some salt water on them. 
 As the latex oozes out it is partially coagulated by the salt 
 with which it comes in contact, and in this state it is 
 picked off the cut by the collector, who rolls it into a ball 
 with his hands; owing to the rapidity of the coagulation 
 with the salt, the latex is stiff enough to be drawn into 
 threads, and long lengths of such thread are gradually 
 wound up into a ball. They cannot be unwound again, as 
 they unite into one mass. Rubber balls prepared in this 
 way are known in the English market as “niggers,” and the 
 adjective “niggery” is often applied to them as a matter of 
 convenience in the rubber works, without leave having been 
 obtained from any authorities on the English language. 
 To revert, however, for a moment to these balls, they are 
 often as much as 2 lbs. in weight, and indeed have 
 been known to weigh 4^ lbs. In making balls of this 
 size, the collector lies down on his back and continues 
 rolling up the rubber while the ball is supported on his 
 body. 
 
 The alum method, known also, from the name of its 
 introducer, as the Strauss method, has been unfavourably 
 reported upon, as the chemical has a deteriorating effect 
 upon the rubber. Indeed, much the same can be said 
 of a good many of the chemical precipitation processes, 
 which owe their origin to a desire to get the necessary 
 work done in as expeditious a manner as possible by 
 any available means. The more these methods come 
 under the ken of the rubber expert the louder are their 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 29 
 
 obvious imperfections likely to be proclaimed, and the 
 nearer shall we approach to the period when this class 
 of work will proceed generally on lines dictated by 
 science. 
 
 Briefly summarised, the points which call for special 
 attention, leaving out of account the wasteful destruction of 
 trees by felling, are :— 
 
 1. More careful tapping so that other juices in the trees 
 shall not be allowed to mix with the rubber latex. 
 
 2. The injudicious mixing of juices of other trees 
 with the rubber latex for the purpose of adding to the 
 bulk. 
 
 3. The removal or sterilization of the fermentible albu¬ 
 minous matter present in greater or less quantity in all 
 rubber latices. 
 
 All three points are generally recognised as of importance, 
 and the two first may be dismissed as outside the pale of 
 controversy. With regard to the albuminous matters, 
 however, Weber has asserted that their presence in small 
 quantities in washed and dried rubber cannot be looked 
 upon as an incentive to decay, because the albumen is now 
 in the insoluble condition. Whether this he the fact or not, 
 there yet remain notable reasons why albuminous matters 
 should be eliminated as far as possible from the raw rubber 
 in the course of coagulation. Apart from the action which 
 their fermentation in the course of transit and during 
 storage exerts upon the rubber itself, there is the nuisance 
 caused by the smell they give, a nuisance which has given 
 rise to legal proceedings in connection both with the 
 broker’s store-rooms and the rubber factories. The above 
 statement of Weber’s must not be read as if he thought the 
 
30 
 
 INDIA-RUBBER. 
 
 presence of albuminous matters in the raw rubber of no 
 importance, as the proposals he made with regard to the 
 use of formaldehyde and other antiseptics during coagulation 
 point in the contrary direction. 
 
 A few analytical figures relating to African rubber are 
 given below. 
 
 The first analysis refers to some samples of rubber latex, 
 which the author received from the Colonial Office sixteen 
 years ago, at the very commencement of the Lagos rubber 
 industry, and they are of special interest when we compare 
 the improvement as regards resinous matters shown in 
 succeeding years. The five samples referred to different 
 varieties of the Ficus Vogelii. Nothing had been mixed with 
 the latex to retard coagulation, but this had only taken place 
 in three out of fifteen bottles sent. The bottles were under 
 considerable pressure from carbonic acid, the rubber latex 
 having a strongly acid reaction. It contained, besides 
 resins, small quantities of tannin glucose and albumen. 
 
 Rubber Latex, Lagos Coast. 
 
 Sample. 
 
 Rubber, per cent. 
 
 Resin, per cent, on 
 the Dried Rubber. 
 
 No. 1 
 
 30-0 
 
 31-5 
 
 No. 2 
 
 28-5 
 
 32-1 
 
 No. 3 
 
 24-5 
 
 32-0 
 
 No. 4 
 
 24-0 
 
 33-0 
 
 No. 5 
 
 21-0 
 
 31-0 
 
 Yield of Rubber per 
 Gallon of Milk. 
 
 lbs. ozs. 
 
 2 13 £ 
 2 11 
 2 7f 
 2 5 
 
 2 Of 
 
 It was explained that the samples were gathered at the 
 wrong time of the year, and would consequently be under 
 strength. 
 
 The raw rubbers known to commerce can be roughly 
 
PRODUCTION OP RAW INDIA-RUBBER. 
 
 31 
 
 classified, with regard to their origin, into four main 
 divisions :— 
 
 1. American j South American - 
 ' Central American. 
 
 2 African f West and Central African. 
 
 i East African and Madagascar. 
 
 3. Asiatic. 
 
 4. Australasian. 
 
 The actual designation under which the various sorts 
 come on the market is derived in many cases from the 
 export station; in other cases from the actual localities 
 whence they are gathered. Again, they may be known 
 simply from their physical state: thus we have such names 
 as Gold Coast “thimbles,” Mozambique “sausage,” and 
 “ biscuits,” “ balls,” “ tongues,” “ flake,” etc. Altogether, the 
 nomenclature is of a rough and ready kind, and, moreover, the 
 last twenty or thirty years have witnessed several changes 
 of names, especially in West African sorts. New sorts also 
 are continually coming into the market, while those which 
 were once well known to the older manufacturers have from 
 one cause or another ceased to have any commercial 
 importance. Where such changes occur, it will be recog¬ 
 nised that it is of little value to give details which in a 
 short period may be out of date, that is where an exhaustive 
 summary is aimed at. Moreover, a detailed list of the 
 rubbers of commerce would probably be of little attraction 
 to that class for whom this work is more especially written. 
 It is proposed, therefore, to limit the information on this 
 head to a short review of the more important brands of 
 rubber which are now coming with regularity upon the 
 
32 
 
 INDIA-RUBBER. 
 
 market. Those who require further detail on this and other 
 points relating to the natural history of india-rubber are 
 recommended to refer to the English translation of Franz 
 Clouth’s book on “ Rubber, Gutta-percha, and Balata,” the 
 author having, with the assistance of Leon Brasse’s investiga¬ 
 tions, put into a concentrated form a large amount of 
 botanical matter. Pearson’s book may also he consulted 
 for details regarding the occurrence of the various brands 
 of rubber. 
 
 Names and Principal Characteristics of the Chief 
 Crude Rubbers of Commerce. 
 
 I. South America. 
 
 1. Para .—Fine Para like the other Para sorts to be 
 mentioned, is derived from various species of Hevea, the 
 bulk of the supply coming from Hevea Braziliensis. It 
 comes in the form of loaves or biscuits of several pounds’ 
 weight, which are of a cream colour internally, though the 
 exterior is usually a dark brown or black. The biscuits are 
 built up in concentric layers of thin sheets, a result of the 
 curing process. The characteristic smell of wood creosote 
 is always present. 
 
 Fine Para rubber, which is the best and forms the 
 standard by which all other sorts are valued, varies slightly 
 in its properties and price according as it is “ Up-river 
 hard cure ” or “ Island soft cure.” The former comes 
 mostly from the wooded regions far up the Amazon valley, 
 being shipped from Manaos, while the latter is chiefly 
 obtained from the islands near the mouth of the river. The 
 two brands are very similar in appearance, though the 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 33 
 
 “ Up-river ” rubber generally comes in larger loaves or 
 biscuits than the “Island,” weighing, indeed, as much as 
 100 lhs. each biscuit. 
 
 A second grade is known as “ Entrefine.” It has a rather 
 lower value owing to its having been imperfectly smoked. 
 
 Then there is what is known as “ virgin ” rubber, which is 
 unsmoked fine rubber, coming in the form of rectangular 
 slabs of a pale yellowish white colour. Its source of origin 
 is mainly Matto-Grosso. 
 
 Fourthly, we have “ Sernamby”or “Negroheads,” already 
 referred to, which consists of irregular lumps of fine rubber 
 mixed with a good deal of bark, and often earthy matter. 
 This rubber is the scrap which is obtained from the trees 
 and the ground where it has escaped collection in the cups; 
 there are also the residues which have coagulated in the 
 cups. From these sources the heterogeneous rubber known 
 as “ Negrohead ” is derived. Though nominally the same 
 rubber as the fine Para, it has suffered by the irregularities 
 in its coagulations, and after allowing for its extraneous im¬ 
 purities it always has a lower value than the other Para sorts. 
 
 The fifth and last rubber to be mentioned under the 
 head of Para is “ Cameta,” which has only in the last ten 
 years become of importance on the European markets. The 
 name is derived from the part on the Tocantins river, south 
 of Para. It is unsmoked and appears to vary a good deal 
 in the amount of its impurities, which are of an albuminoid 
 rather than fibrous nature. It comes in the form of balls, 
 cups, and slabs ; these are usually very moist and clayey, 
 leading to a very high loss in washing; for the rest, the 
 rubber is hard and of good colour and texture. 
 
 2. Peruvian Ball and Slab .—Although Peru yields a good 
 
 I.R. 
 
 D 
 
34 
 
 INDIA-RUBBER. 
 
 deal of fine Para rubber, its more particular product is a 
 second-rate brand known as “Caucho,” more closely approxi¬ 
 mating in its qualities to Central than South American 
 rubbers. A few years ago it was comparatively little known 
 on the European markets, being chiefly used in the United 
 States. It is not cured by smoking but is coagulated by 
 some alkaline solution, or by the addition of soap. The tree 
 has recently been identified by Uhl as a Castilloa, and has 
 been named Castilloa Ulei by Warburg. Of late this rubber 
 has been extensively used in Great Britain as a medium 
 quality. Coming in large quantities and of fairly regular 
 quality, it suits the trade better than other brands which 
 only arrive spasmodically. 
 
 3. Bolivian, in the forms of “ fine,” “ entrafine ” and 
 “ Negroheads,” is practically the same rubber as Para. 
 Owing to its careful preparation and greater dryness, it 
 commands the highest price among raw rubbers. 
 
 4. Pernambuco or Mangabeira rubber is derived from a 
 Hancornia species and comes in wet rectangular slabs, often 
 containing an excess of impurities. Coagulation is usually 
 effected by alum. It arrives only in limited quantities and 
 is evidently one of those brands which would benefit under 
 more scientific and careful collection and preparation. 
 Maranham is another variety derived from the State of that 
 name. These rubbers are rather inelastic and usually 
 arrive in a very wet state. 
 
 What is known as Pernambuco and Assare scrap much 
 resembles Ceara scrap, being collected in the same manner. 
 It is even more sandy and barky and its stickiness renders 
 it difficult to clean thoroughly. It shows a very variable 
 loss in washing. 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 35 
 
 5. Bahia rubber comes from the Brazilian province of 
 Bahia. The tree is one of the Hancornia species, and the 
 rubber, which comes in lumps or slabs, is found to be of 
 variable quality, some of it being almost as strong as Para. 
 
 6. Columbian, also known as “Cartagena,” is derived from 
 
 FIG. 6. — CASTILLO A ELASTICA. 
 
 trees the identity of which is not well established. It is 
 possibly, in its many forms of sheet and strip, a product 
 both of Hevea trees and of the Castilloa elastica. The 
 production seems to have decreased of late years. The large 
 balls or slabs, in which form it is also exported, are black 
 on the outside and a dark grey internally. Coagulation is 
 
 d 2 
 
36 
 
 INDIA-RUBBER. 
 
 carried out by various methods, of which the use of the 
 bindweed milk may be mentioned, though this is said by 
 some authorities to produce an inferior rubber to what can 
 be obtained by other methods. 
 
 The same remarks as to improvement in the method of 
 collection apply here as to the Pernambuco rubber. 
 
 7. Guayaquil rubber, which comes from Ecuador, has 
 much the same origin and characteristics as the preceding. 
 The best quality has a whitish cut, while inferior sorts are 
 extremely porous and contain a good deal of decomposing 
 albuminous matters. 
 
 8. Gear a rubber is obtained from the Manihot glaziovii, 
 in the province of Ceara, Brazil. It is a very dry tough 
 rubber, coming in the form of a mass of shreds or ribbons. 
 It is allowed to coagulate on the tree as it exudes and always 
 contains bark and dirt. Owing to its nature it is not in 
 general demand, there being considerable difficulty in free¬ 
 ing it entirely from its impurities. The Ceara “Negrohead” 
 is more sought after. 
 
 Central America. 
 
 The indigenous tree in Central America and Mexico is the 
 Castilloa elastica, and the rubbers to be referred to are all 
 derived from it or from allied species. Their variations as 
 regards quality and market price must be attributed to the 
 greater or less care with which they are gathered and 
 prepared. In this summary it has been thought advisable to 
 adhere to geographical limits and not to include the produce of 
 the northern part of South America proper among “Central” 
 brands. In trade circles, however, it has become customary 
 to refer to all rubbers obtained north of the Amazon valley 
 
PRODUCTION OF RAW INDIA-RUBBER, 
 
 37 
 
 up to Mexico as “Centrals,” and there is good reason for this 
 on account of practically all of them being yielded by the 
 same species of tree and being of much the same value in 
 the manufacture. The point is not, of course, an important 
 one, and needs no further reference. 
 
 The usual method of coagulating the latex is with the 
 juice of the bindweed, though procedure in the different 
 countries is by no means uniform. According to Pearson, 
 the consumption of Central American rubbers in the United 
 States has much decreased in late years and only small lots 
 find their way to Europe. 
 
 Another trade name for Central American rubber is 
 “ West Indian,” though none of it actually comes from the 
 islands. 
 
 1. Nicaragua rubber comes in scrap and sheets of an 
 almost black colour. Greytown is the shipping port both 
 for this rubber and also for some of that derived from 
 neighbouring States. 
 
 The quality of this rubber is often very high and it comes 
 to the market in a drier state than many varieties of 
 “Centrals.” Indeed, it is considered by many to rank 
 directly after Para. 
 
 2. Panama rubber may be considered together with that 
 from Costa Pica and Honduras; what is shipped at Panama 
 being as a rule mixed up lots collected from different States, 
 not only in Central America but also in the north of South 
 America. All these are the reputed product of the Castilloa, 
 though there are variations in the methods of coagulation 
 practised. Certain species of Hevea trees are also reported 
 as being tapped along with the Castilloas in this area. 
 
 3. Guatemala sheet comes from the State of that name, 
 
38 
 
 INDIA-RUBBER. 
 
 and can always be recognised by the strong smelling 
 characteristic viscous liquid it contains. It is usually 
 coagulated with bindweed juice and there is little doubt 
 that the quality could be much improved by more careful 
 preparation. 
 
 4. Mexican rubber, which is produced in dark strips, has 
 shown a decreased output in recent years, and is now of 
 little importance in the European markets. As, however, 
 the numerous plantations have now begun to yield, there is 
 every probability of the country regaining its original 
 position as a producer. The Castilloa elastica is the common 
 tree, and coagulation is usually effected by boiling the latex 
 with the addition of water. The small balls of this rubber 
 are of much superior quality to the more common form of 
 large slabs. 
 
 II .—African Brands. 
 
 As already mentioned, large quantities of rubber come 
 from Africa, and despite a noticeable diminution from 
 certain districts the total output shows a continual increase. 
 In the following account the principal kinds, which are 
 more or less in regular use in British rubber factories, are 
 referred to, though not necessarily in order of merit. 
 
 1. Gambia is a very useful rubber for general purposes. 
 It comes mostly in mottled, stringy, wet balls, and like most 
 other African sorts, it is usually graded into four standards. 
 Though a fairly hard rubber as a rule, it is often mixed 
 with an inferior latex. 
 
 2. Sierra Leone or Massai rubbers are of somewhat 
 variable name and origin. They come in the form known 
 as “ niggers,” which have been previously described. These 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 39 
 
 are either red or white, the former being the most sought 
 after. They are often mixed with Conakry, and the better 
 qualities of Soudan “ niggers,” etc. The selected, or first 
 grade, is a very useful hard rubber, fairly clean, and it is 
 often bought months ahead by some manufacturers. The 
 other grades very often contain heated centres, besides 
 being more dirty. These rubbers also come in the 
 form of twists, which though a sound and useful rubber, 
 are not so clean or in such good condition as the red 
 “ niggers.” 
 
 3. Gold Coast. This rubber is known chiefly in the form 
 of lumps or slabs, and in small quantities also as “ niggers.” 
 The Gold Coast lumps are usually very wet, and when cut 
 show a yellowish-white colour. The interior of the lumps 
 are more or less spongy, and nearly always full of water 
 and uncoagulated latex, which naturally means a high loss 
 on washing. They are made up into two standards, Coast 
 selected or Liverpool selected as firsts, the softer and more 
 resinous lumps being classified as seconds. The rubber 
 is fairly clean, and always in good demand, though its smell 
 derived from fermenting nitrogenous matters makes it 
 objectionable for some purposes. The outsides of the 
 lumps are quite black and often very dirty, and some 
 manufacturers make two grades by cutting off the outsides, 
 and using them for one purpose and the insides for 
 another. 
 
 4. Benin lump is very similar to that last described, hut 
 usually firmer, of a closer grain, and not so spongy. It has 
 a yellow or bluish tint when cut, the colour being usually 
 deeper than in the Gold Coast lump. Like the latter, it is 
 divided into two grades for sale. 
 
40 
 
 INDIA-RUBBER. 
 
 5. Lagos lump .—The foregoing remarks apply to this, but 
 it is perhaps not quite so uniform in quality as the Benin, 
 The best selected, however, is one of the best lump rubbers, 
 being usually firmer and less resinous than the Gold Coast. 
 It can be distinguished from other brands by its peculiar 
 odour. 
 
 6. Liberian .—This is a lump rubber of rather variable 
 composition, and is not in great favour owing to its most 
 objectionable smell. On being cut open it shows variable 
 tints, from yellow to blue, the latter being generally con¬ 
 sidered the best quality. When the newly floated Liberian 
 Rubber Company has got thoroughly to work, no doubt we 
 shall see this rubber arrive in a condition which will ensure 
 it a better reception than is at present the case. 
 
 7. Niger .—This usually comes in bags in a solid mass, 
 which would be better described as slab than under its usual 
 name “niggers.” The colour varies from grey to red, some¬ 
 times, indeed, being almost black, as a result of over-heating. 
 A large proportion of red bark and dirt is also present, and 
 this means a good deal of trouble in washing. A drawback 
 to this rubber is that the colouring matter from the red bark 
 is apt to remain in the washed rubber, and this if used for 
 a white compound spoils the shade. Some of this rubber is 
 soft and resinous, and comes on the market as Niger gutta 
 or paste. This rubber would be much more useful if more 
 care were taken in its collection and preparation, and in 
 packing for transport. 
 
 8. Mozambique, a very strong and elastic rubber, comes 
 chiefly in the form of stringy balls of various size, and also 
 as sausages, that is, strings of rubber wound round pieces of 
 stick, which entail a good deal of trouble in their extraction; 
 
PRODUCTION OF RAW INDIA-RUBBER, 
 
 41 
 
 also it is found in the form of smooth cakes, to which the 
 descriptive name of “liver ” has been applied. All classes 
 of Mozambique rubber find a ready sale. 
 
 9. Madagascar, which principally comes as irregular cakes, 
 is generally referred to as pinky Madagascar, owing to its 
 characteristic colour. It is a good, clean and useful rubber. 
 The Majunga balls are not so clean, and very often contain 
 some of the pinky rubber found in these centres. Another 
 grade, known as East and West Coast “niggers,” is usually 
 very dirty, and this detracts a good deal from what would 
 otherwise be a very strong and elastic rubber. 
 
 10. Congo sorts .—The various grades of rubber coming 
 from the Congo Free State are in great demand, as they bear 
 the impress of a more careful preparation than is the case 
 with the bulk of the West African sorts. They come chiefly 
 in the form of small balls and strips, and are known under 
 many distinctive names, according to their gathering grounds. 
 Among the Upper Congo sorts best known in England are 
 Aruwimi, in the form of large balls, often heated in the 
 interior; Equateur, small balls, usually dry and clean; 
 Lopori, coming in ball, strip and sausage of very varying 
 quality; Uelle, in strips and cakes of rather low quality; 
 Mongalla, which arrives in ball and strip of good quality; 
 and lastly, Wamba thimbles, also of good quality. 
 
 As the loss of these rubbers in washing varies to such a 
 great extent in different lots, it has not been thought desir¬ 
 able to give any figures in the table of losses in washing to 
 be found further on. With regard to the variation in 
 quality often found in particular brands, there seems little 
 doubt that fermentation setting in in the hold of the steamer 
 is frequently the cause, and more careful conditions of 
 
42 
 
 INDIA-BUBBEE. 
 
 transit might be adopted with advantage. Antwerp is the 
 principal market for these rubbers, and they are not sold by 
 auction, as in England, but by tenders received on the 
 strength of sample lots which have been sent to prospective 
 purchasers. 
 
 III .—Asiatic Brands. 
 
 The Ficus clastica is the principal rubber-producing tree 
 of Eastern Asia, though recent botanical research has 
 caused the identification of distinct though allied species. 
 The rubber is not of the same high quality as the Para, and 
 it is noteworthy that in the plantations now springing up 
 in such profusion in the East general attention is being 
 restricted to the cultivation of the acclimatised Hevea trees 
 to the almost total neglect of the indigenous species. 
 Compared with the imports from South America and 
 Africa the amount of Asiatic rubber which comes to 
 England is quite insignificant. These rubbers, particularly 
 in the lower grades, are somewhat inelastic; they contain a 
 large quantity of fibrous and earthy matter, and show a 
 tendency to heat, i.e., become sticky very quickly. 
 
 1. Assam rubber is prepared in the form of balls com¬ 
 posed of the strings of rubber which have been allowed to 
 coagulate on the trees. There are four grades of it, differing 
 a good deal in their quality. This rubber was first exported 
 to London in 1828, and, as we shall see in another chapter, 
 it was the decreased yield in this part of the world which 
 gave rise to the idea of rubber planting. This rubber 
 contains a very hard resin as well as a soft one, their 
 respective melting points being 82° C. and 12° C. 
 
 2. Rangoon rubber comes from Burma, and much 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 43 
 
 resembles the Assam. Its output in recent years has 
 increased, while the Assam supply has diminished. 
 
 3. Penang comes principally from the island of that name, 
 and also from the Sunda islands, in the form of balls, slabs, 
 and “ sausages ” of a reddish colour. It varies very much in 
 
 FIG. 7 . — FICUS ELASTICA. 
 
 quality, and is generally inferior both as regards impurities 
 and elasticity to the Assam and Rangoon rubbers. 
 
 4. Java rubber differs but slightly from Assam, though it 
 can generally be distinguished by its darker tint and 
 occasional red streaks. Admixture with gutta-percha is not 
 unknown. 
 
 5. Borneo rubber is not in much demand on account of 
 the amount of water and dirt it usually contains. In 
 
44 
 
 INDIA-RUBBER. 
 
 general appearance it comes in slabs of a whitish colour, 
 turning pink when stored for any length of time. It 
 contains, or used to do so, a good deal of a curious volatile 
 sugary substance, first extracted by Girard in 1871, and 
 called by him “bornesite.” A very similar body had pre¬ 
 viously been found by him in the Gaboon rubber of West 
 Africa. 
 
 Whether this is a natural constituent of the latex or is 
 an adulterant added by the native collectors does not seem 
 to have been satisfactorily cleared up. Borneo rubber 
 usually arrives very wet, and is apt to contain many small 
 pieces of wood, which are not detected until the balls or 
 slabs are cut up small. The lower qualities are also very 
 gritty and dirty. This rubber is always characterised by its 
 white colour and great humidity. It is the product of the 
 Urceola elastica, a tree which has been known to send out 
 lianes 180 metres long, according to Chapel. 
 
 IY .—A ustralasian. 
 
 Of even less importance commercially than the wild 
 Asiatic supply is that which comes from Australasia from 
 certain species of Ficus :— 
 
 1. New Guinea balls come in the form of strings of 
 small balls, sometimes of superior quality, but showing 
 great variations in this respect. 
 
 2. New Caledonia rubber, which is quite a recent intro¬ 
 duction to the European market, besides coming in balls is 
 also found in the biscuit form like Sara. 
 
 8. Noumea is another rubber similar in almost every way 
 to the last named. 
 
PRODUCTION OP RAW INDIA-RUBBER. 
 
 4o 
 
 Pseudo Rubbers. 
 
 The raw rubbers which have been mentioned, as well as 
 several more which have not been specifically referred to, 
 by no means comprise all the crude material which the 
 tropical forest supplies to the rubber trade. There are 
 several substances which, for want of a better term, are 
 known as “pseudo rubbers,” which come into the market 
 in greater or less quantities. Some of them resemble 
 rubber, some gutta-percha, while others are practically 
 all resin. There is little doubt that in parts of Africa 
 the natives mix resinous latices of this class with the 
 rubber so as to increase the bulk. Looking at the various 
 pseudo rubbers which have appeared in the market so far, 
 the chief point about them is their slight value compared 
 with sound rubber. They are referred to as low grade 
 rubbers, but as they consist for the most part of resins, it 
 would be more correct to term them superior resins, superior 
 that is for rubber-manufacturing purposes. One of these 
 bodies, known variously as potato rubber, almeidina or 
 euphorbia gum, was introduced into England more than 
 twenty years ago by a London firm of produce brokers. On 
 the strength of its supposed properties some rubber manufac¬ 
 turers bought a good deal of it at 6d. per lb. (Fine Para being 
 then 2s. Qd .per lb.),but had cause to repent the transaction. 
 The potato rubber, so called from the form in which it is 
 imported, is obtained from the tuber-like roots of a tree or 
 shrub which has been found principally in Portuguese West 
 Africa, the Cameroons and the Solomon Islands. Its com¬ 
 position, roughly speaking, is 90 resin and 10 rubber. 
 It will be seen, then, that its value is very small, and what 
 
46 
 
 INDIA-RUBBER. 
 
 was bought on its introduction at 6d. per lb. was afterwards 
 valued at 2 d. In recent years it has not increased in favour, 
 as it can only be used in admixture with rubber for certain 
 low quality goods, and even then, in the author’s opinion, 
 it could be profitably dispensed with in favour of other 
 material. When put into boiling water potato rubber can 
 be drawn out into threads. A rather curious point about the 
 substance is its supposed poisonous properties, men who 
 have worked it on the hot rollers complaining generally of 
 the effect of a pungent vapour it gives off. Whether this 
 effect is due merely to an irritant or to some specific poison 
 does not seem to have yet been determined. Another body 
 which has been used in large quantities in recent years is 
 Pontianak, also called Jelutong in the United States. It 
 comes from the town of Pontianak, in Borneo, in white 
 lumps, smelling strongly of petroleum. Its composition in 
 the dry state is 75 to 90 per cent, resins, and 25 to 
 10 per cent, rubber-like substance. The increased demand 
 indicates that it is of more value than potato rubber, 
 though it has hardly any claim to be considered 
 as a raw rubber. It has been used to some extent in 
 England as a binding material in the reclaimed rubber 
 manufacture, and, it is said, is now being used for proofing 
 purposes. In America it has had a wider application in 
 connection with the rubber manufacture. 
 
 The removal of the resins by solvents formed the basis 
 of a secret process recently exploited for the treatment of 
 Pontianak, but it is difficult to see how any such project 
 could be financially successful, because not only is the 
 proportion of resin very large, but the purified rubber is 
 only of low quality. With regard to the production of 
 
PRODUCTION OF RAW INDIA-RUBBER, 47 
 
 Pontianak, it is got from the tree known as By era costulata, 
 by breaking the bark and allowing the resinous exudation 
 to collect in tins. The coagulation, or rather preparation, 
 is effected by mixing it with water and petroleum spirit, a 
 small quantity of a special powder obtained from China 
 being also added. This powder has been shown to consist 
 of fibrous gypsum, and its supposed utility is not apparent. 
 The above materials having been well mixed together the 
 product is rolled into the balls in which it is exported. 
 Although numerous other substances have a legitimate 
 claim for consideration here, there are only two more 
 which seem to have any regular use. These are Chicle 
 gum, obtained from the Achras saytota, a common Central 
 American and Mexican tree, and Tuno, which is the 
 coagulated latex of the sterile rubber tree of Nicaragua and 
 Honduras. The latter is said to be used in conjunction 
 with balata in the belting manufacture, while the former, 
 though its principal application is in the chewing-gum 
 business, is reputed to he used in connection with rubber 
 insulation. These last products are very little in evidence 
 on the European rubber market, the United States taking 
 the bulk of the output. 
 
 Congo India-rubber. 
 
 It is a good many years ago since Stanley prophesied the 
 future greatness of the district known now as the Congo 
 T i’G6 State as a source of india-rubber. At the time non¬ 
 expert writers saw in this announcement the impending- 
 fall of Brazil from her high position as the principal source 
 of the world’s supply. The fact that the Congo region 
 produces no rubber of anything like the high quality of 
 
48 
 
 INDIA-RUBBER 
 
 that of Brazil was entirely ignored. Before 1890 there 
 was practically no raw rubber market at Antwerp. In 
 that year the rubber changing hands amounted to thirty 
 tons, five years later it rose to five hundred and thirty-one 
 tons, while successive years showed rapid increases to the 
 neighbourhood of six thousand tons in 1900, although it 
 should be mentioned that the Antwerp imports are not by any 
 means confined to rubber from the Congo State. One result 
 of the methods employed is that large areas in readily avail¬ 
 able districts have been rapidly depleted, a circumstance 
 which is reflected in the diminution shown in the exports to 
 Antwerp in 1902. A word or two may be said on technical 
 points, though much that bears upon these has already had 
 mention in other chapters. The trees belong almost entirely 
 to the Landolphia class, already mentioned as giant creepers, 
 and owing to the density of the forests rubber-bearing parts 
 often have to be cut away at a considerable height where 
 they have climbed towards the light by the support of the 
 other trees. This necessitates a good deal of climbing, 
 adding considerably to the ordinary danger and labour 
 associated with rubber gathering. With regard to the 
 rubber itself a great improvement is noticeable compared 
 with the Landolphia rubber shipped from the Congo region 
 twenty years ago. Not only has the open sophistication 
 with extraneous matter ceased—this was only to be 
 expected in the circumstances—but the coagulation of the 
 rubber latex is being carried out on lines which give a 
 superior product. More attention is now being paid than 
 at first to drying the coagulated rubber out of the direct 
 rays of the sun, a procedure that led to a superficial sticky 
 composition. No doubt also we may look for improvements 
 
PEODUCTION OP RAW INDIA-RUBBER. 49 
 
 in coagulation which will give the manufacturers less reason 
 to complain of “ sweated ” rubber. This not very appro¬ 
 priate name is given to rubber which on arrival in Europe 
 shows a sticky decomposition in the interior of the balls, 
 due no doubt to fermentation of albuminous matters. 
 
 FIG. 8.—LANDOLPHIA OWARIENSIS. 
 
 That considerable improvement is already shown in West 
 Coast rubbers generally is testified by the keenness of the 
 British in bidding at the Antwerp sales. 
 
 Raw Rubber: Some General Considerations. 
 
 We may briefly discuss now one or two points of some 
 importance with regard to the collection and exportation of 
 
 I.E. 
 
 E 
 
50 
 
 INDIA-RUBBER 
 
 rubber. It is not surprising that the increase of intelli¬ 
 gent supervision has led in some cases, and promises to do 
 so in others, to an improvement in the methods of tapping, 
 coagulation and other processes by which the rubber is 
 prepared for export. Originally all this technical work was 
 left entirely to the native collector, who operated according 
 to his own lights, and it certainly seems more in accord 
 with the fitness of things that a commodity of such a high 
 value should receive skilled supervision in its preparation 
 as well as in its manufacture. Of course the chief diffi¬ 
 culty lies in the practical impossibility of exercising super¬ 
 vision over the natives who carry on their work at scattered 
 points in the depths of the forests, and where, moreover, 
 the climatic conditions are apt to prove rapidly fatal to 
 
 Europeans. It is easier to say what is desirable than to 
 
 indicate precise methods for accomplishing the ends desired. 
 There is plenty of evidence, however, that those who are 
 concerned with the harvesting of the rubber crop, especially 
 in West Africa, are likely in the future to achieve consider¬ 
 able success as a result of the reforms which have been 
 
 initiated, and which are being pushed with all the energy 
 that circumstances will allow. The wholesale destruction 
 of trees has in most of the districts been forbidden by law, 
 and where the yield of certain areas has suffered serious 
 diminution owing to the reckless gathering, laws have been 
 passed prohibiting the export for a certain period of time. 
 This was done, for instance, in the case of Lagos rubber. 
 Owing to the great falling off in the export a few years ago, 
 the gathering was prohibited for five years. Lagos rubber, 
 which on its first introduction in 1890 was not highly 
 thought of by the manufacturers, owing to its high content 
 
PRODUCTION OP RAW INDIA-RUBBER. 
 
 51 
 
 of resins, was later received with greater favour owing to 
 the improvement shown in its quality. 1 It was not un¬ 
 natural, then, that the threatened collapse of an industry 
 which was an important source of revenue to the colony in 
 the way of export duties should have been regarded with 
 apprehension by the authorities, and it will be admitted 
 that the somewhat drastic steps taken to insure the future 
 of the industry were conceived in the best interests of all 
 concerned. Experimental work is being actively carried on 
 by botanists at several Government botanical gardens, as 
 well as by private individuals; the work of the Liverpool 
 Institution of Tropical Research should also be mentioned 
 in this connection. A feature of the situation is the great 
 increase of interest in the raw rubber supply which is being- 
 evinced by the manufacturers, compared with what obtained 
 twenty years ago. The community of interests needs no 
 emphasis, and those who are working on the botanical side 
 have now little or nothing to complain of with regard to the 
 attitude taken up by the manufacturers respecting then- 
 work. Here, without wishing in any way to be didactic, 
 the author feels constrained to pass a word of comment on 
 a certain matter. A tendency is noticeable among the new 
 scientific investigators to show impatience at the caution 
 evinced by manufacturers in buying any new product. The 
 experience gained in years of work in the factory, largely 
 empirical though it may be, enables the manufacturer to 
 lay a safe course, and he knows that any deviation 
 may prove disastrous. It is not surprising, therefore, 
 that the enthusiastic investigator often finds him slow to 
 recognise the importance of a discovery and its predicted 
 1 Recently, however, it has again deteriorated. 
 
 E 2 
 
52 
 
 INDIA-RUBBER. 
 
 far-reaching effect upon the trade. The practical man in 
 the rubber factory has often failed to receive justice at the 
 hands of scientific writers, but those who really know the 
 trade, its intricacies and its pitfalls, will be slow to condemn 
 his conservatism. When he is shown half-an-ounce of an 
 inferior rubber transmuted by up-to-date methods into 
 Para, his habitual caution arouses a desire to see a ton of it 
 before giving the discovery the seal of his approval. It may 
 be a perfectly practical process as far as he knows, hut he 
 prefers to adopt a negative attitude until he is satisfied on 
 all material points. The period of probation, then, must 
 perforce he somewhat lengthy; hut apart from this it may 
 be taken that, the interest of the manufacturers having now 
 been aroused, their support and encouragement will continue 
 to be at the service of those who from one cause or another 
 are endeavouring to utilise to greater economic advantage 
 the natural resources of the rubber forests. The improve¬ 
 ments which have been already effected in the preparation 
 of several of the West African brands of rubber will no 
 doubt in the course of time be extended to others. There 
 is no good exporting sand, fibre and water, and the practice 
 of mixing the resinous saps of other trees with the rubber in 
 order to swell the hulk has certainly no justification. More¬ 
 over, the over-heating of the rubber, due to exposure to the 
 sun’s rays, is a source of damage that could no doubt be 
 largely minimised. At the same time, speaking more par¬ 
 ticularly of mechanical impurities, it is not at all clear that 
 their removal by the exporter is a matter of expediency. 
 To take a concrete instance, the British manufacturer com¬ 
 plains of the amount of sand and fibre which he gets with 
 the Ceara rubber ; he says it ought to be exported in a 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 53 
 
 cleaner state. As a matter of fact, the collectors in Ceara 
 have gone into the case carefully, and find that the differ¬ 
 ence in the price which they can obtain for the purified 
 rubber does not pay them for the extra labour involved. 
 This, of course, does not answer the whole objection; it 
 remains to be seen whether the rubber cannot be prepared 
 in such a way that sand and bark are not allowed to get 
 intermixed with it. Until a new method of procedure is 
 evolved, the rubber will continue to be shipped in an impure 
 state. Possibly this case has its parallels in West Africa, 
 and before we can expect the rubbers in a cleaner condition 
 it will have to be shown that the necessary work will prove 
 remunerative to the exporters, including in this term the 
 collectors. Turning to another matter, nothing seems to 
 have been advanced in recent years in support of the 
 idea that rubber of an inferior quality would be found 
 equal to Para rubber if its impurities, especially its resins, 
 were removed. The whole subject is a very intricate one, 
 and on the present occasion it is sufficient to state that, 
 while some of the Landolphia rubbers when well prepared 
 are quite equal to second-grade Para sorts, yet, whether on 
 account of some chemical difference in the latex, or from 
 the methods adopted in collection and coagulation, the very 
 best rubber has not yet been obtained from other sources 
 than the Para rubber trees of South America. Some years 
 ago the author extracted the resins from a quantity of first 
 quality African ball rubber and had the latter made into 
 elastic thread under ordinary conditions. The product, 
 however, proved to be decidedly inferior to ordinary Para 
 thread in tensile strength. It is not contended that this 
 experiment proves more than that the removal of resins in 
 
54 
 
 INDIA-RUBBER. 
 
 the rubber is useless in order to convert a low grade of rubber 
 into the highest one. It may be shown that the intimate 
 association of the rubber and the resins has permanently 
 damaged the former. Possibly if the resins had never 
 intermingled with the latex, or had been separated from the 
 rubber during coagulation, the latter might have been found 
 to possess better qualities than is ordinarily the case. With 
 few exceptions the attention of planters is being confined to 
 the best quality of rubber; points such as the above will 
 therefore more naturally come under the notice of those 
 who are engaged in exploiting the product of untended 
 nature, or are concerned with the replanting of the 
 indigenous trees in denuded districts. 
 
 Apart from various Congo sorts and the very partial 
 introduction of brands from Australasia, there has not been 
 much of novelty—plantation rubber apart—to engage the 
 manufacturers’ attention lately in the raw rubber market. 
 Reference may, however, be made to the Manicoba rubber, 
 about the origin of which some misunderstanding is current. 
 This rubber is not derived from any new source; it is 
 merely the product of the ordinary Ceara rubber tree, Mani- 
 hot (jlaziovii, grown in Ceara from seed. Of late there has 
 been a disposition among the Cearense to put to use in their 
 own country the knowledge concerning Para rubber which 
 they have acquired when collecting in the Brazilian swamps. 
 An instance of this is seen in the smoked Ceara rubber 
 which is now on the market, and which is known locally as 
 “profumada,” to distinguish it from the ordinary unsmoked 
 sort. The Man^oba rubber is not smoked, and ranks with 
 good second-quality Para sorts. If it were not for the 
 large amount of fine sand which it so often contains, and 
 
PRODUCTION OF RAW INDIA-RUBBER. 55 
 
 which makes it so difficult to thoroughly wash, it could 
 be used for best quality purposes, as it has a high tensile 
 strength. 
 
 Guayule rubber is a new product which calls for more 
 than passing notice, as its preparation involves a somewhat 
 new departure. The plant which yields it (Parthenium 
 argentatum) is found in abundance on large tracts of waste 
 land in Mexico and Texas. It is a shrub containing rubber 
 in its branches, and several patents have been taken out in 
 America in connection with processes for its economical 
 extraction. The yield of rubber has been variously stated, 
 but according to the India-rubber World, which has devoted 
 considerable space to what is being done with Guayule, the 
 yield, as gauged from comprehensive experiments, is 8 per 
 cent, of the refined rubber. As tapping is out of the ques¬ 
 tion, the process adopted consists, roughly speaking, of 
 cutting the shrubs into pieces and separating the rubber 
 substance by maceration in water. There are, however, 
 several patent processes of extraction in operation, and the 
 last word has by no means been said as to which is the most 
 satisfactory method of procedure. The International Guayule 
 Rubber Company has been formed to exploit a large acreage 
 of ground in Mexico, and they estimate that their special 
 machines will extract 3,000 tons per year. Unlike the 
 Colorado rabbit-weed rubber, which has so far utterly failed 
 to substantiate its much-vaunted claims, Guayule rubber is 
 already on the market. Large quantities have been used in 
 America, and it is now before the notice of European 
 manufacturers. With regard to its value, it is pretty clear 
 that this was at first overrated, and it is not surprising that 
 it is now being sold at about half the price originally asked 
 
56 
 
 INDIA-RUBBER. 
 
 for it. A good-class sample recently analysed in the author’s 
 laboratory gave the following figures :— 
 
 Per cent. 
 
 53*02 
 
 21*82 
 
 24*78 
 
 *38 
 
 Eubber 
 Eesins 
 Water 
 Ash . 
 
 100*00 
 
 Time alone will show whether the extraction process will 
 justify the expectations of those who have embarked in the 
 industry with so much enthusiasm, but it is noteworthy 
 that a factory on a large scale is being started in Germany, 
 where, of course, freight will have to be paid on the raw 
 material. 
 
 The Continental Guayule Company, which was recently 
 incorporated under the laws of New Jersey with a large 
 capital, have obtained possession of Lawrence’s American 
 patent for the extraction of guayule. Two or three quite 
 distinct processes are involved in these patents. In one of 
 these the shrubs are put through corrugated rollers and 
 extracted with naphtha. The solution obtained is then dis¬ 
 tilled down to a certain point and alkali is added ; this 
 dissolves the resin and causes the rubber to separate out. 
 In another process the guayule is obtained, as already 
 mentioned, by maceration in water, but it is afterwards 
 treated with wood naphtha or alkali in order to extract the 
 resins. From one or other of these processes a guayule 
 rubber, practically free from resin, has recently been put on 
 the market in trial lots, and as long as the raw material 
 lasts no doubt it will remain a regular article of commerce. 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 57 
 
 It has been stated on page 37 that although the expression 
 West Indian is often used for Central American rubbers no 
 rubber comes actually from the West Indian islands. This 
 is correct for the present, but in all probability the rubber 
 vines which are found in Jamaica will be utilised before 
 long. Samples of the rubber coagulated by exposure to the 
 sun have been examined in England, and the quality is 
 beyond question. According to the Kew authorities, the 
 rubber is yielded by the Forsteronia floribunda. It will 
 probably be found that this creeper is common enough in 
 Hayti and San Domingo, though the weak point about the 
 prospective West Indian wild rubber industry seems to be 
 that its life must inevitably be short. In addition to the 
 limited area of the gathering grounds, there is the fact of 
 it being necessary to destroy the vines to get the rubber. 
 Moreover, replanting of indigenous trees is hardly likely to 
 be carried on, because if anything is done in the plantation 
 way attention will assuredly be concentrated on the Para 
 rubber tree, which yields the best return to the investor. 
 
 The two principal ports into which the raw rubbers referred 
 to in the previous chapter come are Liverpool and London. 
 Their pre-eminence in this respect, as far as continental 
 supplies are concerned, has suffered a serious diminution 
 during the last ten years owing to the rivalry of Antwerp, 
 Hamburg, Rotterdam, Havre, Marseilles and Bordeaux. The 
 great bulk of the supplies comes to brokers who make a 
 speciality of the business, and it is sold by auction to the 
 rubber merchants. Strange though it may seem to the 
 buyers of other commodities in bulk, such as metallic ores 
 and cellulose, chemical analysis is not used at all in deter¬ 
 mining the price to be paid. The ordinary procedure is 
 
58 
 
 INDIA-RUBBER. 
 
 for the merchants to post small sample lots of the rubber 
 on offer to the manufacturers, who buy on the strength of a 
 superficial examination alone. Sometimes the deal is 
 effected on post samples alone, or the manufacturers may send 
 their trained buyers to inspect the bulk. Undoubtedly crude 
 and open to errors as this procedure may be, it still remains 
 for those who have strenuously advocated chemical analysis 
 as the proper basis on which to found ideas as to value to 
 show how the alteration can be carried out. It will be 
 evident from what has been said as to the nature of the raw 
 rubber, its protean forms, and its varied characteristics, that 
 the taking of a correct sample indicative of the bulk, say, of 
 several tons, must prove an exceedingly difficult undertaking, 
 leaving out of consideration altogether the expense which 
 would be involved. Not only does the rubber arrive in most 
 cases in very small pieces, but the contained impurities are 
 very unevenly distributed. As the suggested alteration of 
 procedure has not so far been seriously considered by the 
 trade, its pros and cons need not receive detailed notice 
 here; it will suffice to say with emphasis that any change 
 will have to be made on very carefully considered lines, and 
 that if discrepancies are to be avoided a close understanding 
 must be arrived at between the chemists employed by both 
 buyer and seller as to the actual details of the methods of 
 testing adopted. Even in such a comparatively simple 
 case as the cellulose boards imported into England 
 from Scandinavia for paper-making purposes, it has been 
 found extremely difficult to arrive at the true percentage of 
 moisture, not because of faulty work on the part of individual 
 analysts, but because the water is unevenly distributed in 
 the mass, thus making the sampling procedure a matter of 
 
PRODUCTION OF RAW INDIA-RUBBER, 
 
 59 
 
 the first importance. With regard to fine Para rubber which 
 arrives year by year, of practically uniform composition, 
 there is little or no risk of loss by bad judgment under the 
 prevailing conditions ; it is in the lower grades of rubber, in 
 which the impurities vary to such an extent that the buyer’s 
 faculties of discernment come into prominence. Unlike the 
 tea-taster, who receives a large salary for his work of dis¬ 
 crimination and retires with his health ruined, the raw 
 rubber expert uses only the senses of sight and smell, and 
 if he is not paid on a princely scale it can be said that his 
 work is not of an unhealthy nature, although there certainly 
 are pleasanter substances to associate with than albuminous 
 rubber which is undergoing fermentation in a badly-ventilated 
 building. 
 
 Nowadays the grosser impurities—adulterations would be 
 a more correct term to use in this connection—such as 
 metal, added for weighting purposes, are not met with, and 
 the impurities that have to be ordinarily dealt with consist 
 of sand and w r oody fibre, together with some albuminous 
 and saccharine matter. Water is, of course, always present 
 in greater or less quantity, and there may also be evidence 
 of the chemicals used in coagulation. These impurities 
 have all to be removed, or as far as possible removed, by 
 the manufacturers before the rubber can be used. The sum 
 total of these impurities is known as the “loss in washing,” 
 and the figures for the various brands of rubber are of con¬ 
 siderable importance in the economy of the manufacture. 
 It is not surprising that these figures, as obtained in different 
 works, show considerable variation, particularly in the lower 
 grades of rubber. This is the case in those published by 
 Chapel, Pearson, Clouth, and Weber in their respective 
 
60 
 
 INDIA-RUBBER. 
 
 books. The differences may be attributed to two main 
 causes, the most prominent one being the probable variation 
 in the raw rubbers, and the other the varying degree of 
 exactitude with which the washing and drying operations 
 were carried out. In the following table, which does not 
 claim to be an exhaustive one, will be found figures, kindly 
 furnished by one of our prominent manufacturing firms, as 
 the mean result of their own experience. It is thought that 
 a table giving the recent results of an English firm will 
 prove of more interest than any reproduction of figures 
 already published, authoritative though they may be. 
 
 Another, and the most important, impurity in crude 
 rubber has now to be mentioned. This is the resin, to use 
 the singular number for a group of bodies which are found 
 in the various brands of rubber. Although, of course, their 
 existence was known, nothing definite with regard to them 
 seems to have been published until 1889, when the author 
 read a paper on the subject before the Society of Chemical 
 Industry. 1 In this paper he showed that not only did all 
 the brands of rubber contain resinous bodies largely peculiar 
 to themselves, but that these resins were quite distinct from 
 the oxidation product of vulcanized rubber previously 
 described by Spiller. The further reference to this topic 
 will come more fitly under the head of the chemistry of 
 india-rubber. 
 
 The chief point of practical importance about these 
 resinous matters is that, unlike the other impurities, they 
 are not removed from the rubber in the ordinary washing 
 process, and they therefore form a component part of rubber 
 goods. 
 
 1 Jour. Sue. Chem. Ind... 1889. 
 
PRODUCTION OF RAW INDIA-RUBBER. 
 
 61 
 
 For the sake of convenience, the percentages of resin in 
 the different rubbers are tabulated next to those referring 
 to the loss in washing, the figures being calculated on the 
 washed and dried rubber, and not on the raw product. It 
 is only in this way that comparative figures of any value 
 
 FIG. 9.—CARPODINUS LANCEOLATL'S (AFRICAN ROOT RUBBER). 
 
 can be obtained, otherwise it is obvious that the stated 
 amount of resins would depend as much on the other 
 impurities present as upon the rubber. Since the publica¬ 
 tion of the author’s original paper considerable attention 
 has been paid to the subject of resins in raw rubber, and 
 numerous estimations have been made. Of those who have 
 
62 
 
 INDIA-RUBBER. 
 
 published figures we have C. 0. Weber, 1 Clouth, 2 and L. M. 
 Bourne. 3 As the figures are obtainable by a simple labora¬ 
 tory operation necessitating no particular skill, and as such 
 determination now forms part of the regular routine in the 
 more important factories, it is not proposed to quote any 
 individual authority. The figures given in the table are 
 derived from other sources as well as from the authors’ 
 note-books, and are given as being most generally true for 
 the particular rubber brands concerned :— 
 
 
 Loss on Washing. 
 
 Resin in Washed Rubber. 
 
 A merican — 
 
 Per cent. 
 
 Per cent. 
 
 Para .... 
 
 f 
 
 16—20 
 
 Best 1—4 
 
 2‘5—3'5 
 
 Ceylon Para 
 
 Inferior crepe and 
 
 1-8—2-5 
 
 Sti £iits ,) • • | 
 
 scrap lose a good 
 
 I Do 
 
 i 
 
 deal more. 
 
 I 
 
 Virgin . 
 
 18—22 
 
 2-5 
 
 Negroheads 
 
 40—50 
 
 3—4 
 
 Ceara Scrap 
 
 25—35 
 
 3—4 
 
 Manitoba. 
 
 20—50 
 
 3—4 
 
 Peruvian Ball . 
 
 25—30 
 
 4—5 
 
 Cameta .... 
 
 40—50 
 
 2—3 
 
 Mangabeira 
 
 30—40 
 
 5-6 
 
 African — 
 
 
 
 Red Sierra Leone Niggers 
 
 12—25 
 
 7—9 
 
 Lagos Lump 
 
 40—45 
 
 18—20 
 
 Upper Congo . 
 
 Various 
 
 
 Red Ivassai 
 
 6—8 
 
 4—5 
 
 Benguela .... 
 
 20—30 
 
 4—5 
 
 Mozambique Ball 
 
 12—25 
 
 6—7 
 
 ,, Sausage 
 
 Madagascar Pinky . 
 
 12—25 
 
 6—7 
 
 20—35 
 
 10—11 
 
 The following figures for “loss on washing” are from 
 
 1 Jour. Soc. Chem. Ind., 1894. 
 
 2 Loc. cit. 
 
 3 India-rubber World, December, 1906. 
 
PRODUCTION OF RAW INDIA-RUBBER, 63 
 
 other sources, and are included so as to give a general idea 
 of the Asiatic products :— 
 
 
 Loss on Washing. 
 
 Resin in Washed Rubber. 
 
 Asiatic — 
 
 Per cent. 
 
 Per cent. 
 
 Rangoon .... 
 
 20—30 
 
 5—7 
 
 Penang .... 
 
 10—30 
 
 6—7 
 
 Borneo .... 
 
 20—60 
 
 7—8 
 
 Assam .... 
 
 10—45 
 
 5—9 
 
 Java .... 
 
 10—40 
 
 6—7 
 
 All these are sold in two, three, or more grades, according 
 to their general purity, and it is evident that the figures for 
 loss and resin will vary considerably in the different grades. 
 The raw rubber production of the world for 1906 has been 
 calculated at 65,000 tons, of which 41,000 tons came from 
 tropical America, 22,000 tons from Africa, and 2,000 tons 
 from Asia. 
 
CEAPTEE III. 
 
 CHEMICAL AND PHYSICAL PROPERTIES OF INDIA-RUBBER. 
 
 India-rubber —that is, the purified unmanufactured body— 
 is a tasteless opaque white substance having a more or less 
 pronounced odour, characterised to some extent by its mode 
 of coagulation; in smoked Para the smell of creosote is 
 always perceptible, while the odour of rotten cheese is 
 generally associated with low class brands from Africa and 
 Central America. The specific gravity has been variously 
 stated. Faraday gives it as ‘925, Julian as '920, Weber 
 •915 to -931, while the author, as the result of careful 
 determinations made on Para rubber cleaned and compressed 
 into a block, has found it to be *924. 
 
 Chemically speaking, the analyses made respectively by 
 Faraday, Ure, Greville Williams, Berzelius, Adriani 
 Gladstone and Hibbert, and by Weber amongst the most 
 recent investigators, show that it must be considered a 
 hydrocarbon, of the terpene type, Cio Hi 6 , this formula 
 representing the composition of turpentine. As a matter of 
 fact, however, india-rubber is never found entirely free 
 from oxygen, this element being contained in a small 
 portion of the whole which is insoluble in the ordinary 
 solvents. This insoluble body was first described by Payen 
 and has been studied closely by more recent observers. 
 The statements of some authors as to the amount of this 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 65 
 
 constituent present in ordinary rubber are no doubt greatly 
 exaggerated, Gladstone and Hibbert having found only 
 4 per cent, of it in Para rubber, and Weber, as the result of 
 repeated experiments, from 3 to 6*5 per cent. 
 
 Expressed in percentages, the composition may therefore 
 be taken to be, if we adopt the figures of Gladstone and 
 Hibbert— 
 
 Per cent. 
 
 Carbon . . . . 
 
 . 87-46 
 
 Hydrogen . . . . 
 
 . 12-00 
 
 Oxygen and ash 
 
 '54 
 
 
 100-00 
 
 Into the protracted researches which have been made by 
 various chemists, in recent years, to determine the correct 
 formula and the molecular weight, it is not proposed to 
 enter. Their discussion would lead into scientific regions 
 in which those who are not equipped with a knowledge of 
 organic chemistry would find it difficult to make any 
 headway. The limited space available will, therefore, be 
 utilised for the discussion of matters of easier compre¬ 
 hension, and of more general import with regard to the 
 manufacture. 
 
 India-rubber is quite insoluble in water, but it will absorb 
 about 25 per cent, into its pores after soaking for some 
 time. As showing that rubber is not entirely impervious to 
 water, mention may be made of an interesting experiment 
 carried out by Hancock, who having filled a rubber bag 
 with water and sealed it hermetically, found the weight to 
 continually decrease, until after thirty years it proved 
 on being cut open to be quite dry Alcohol is also absorbed 
 
 I.R. 
 
 F 
 
66 
 
 INDIA-RUBBER. 
 
 by india-rubber, but has no solvent action upon it. With 
 regard to acetone, which was first suggested by Weber as a 
 useful medium in rubber analysis, and has been stated by 
 him to have no solvent action whatever upon the rubber, it 
 would appear from a recent statement of Ditmar that it is 
 not above suspicion in this respect, and that, in fact, it will 
 on occasion dissolve appreciable quantities of rubber. These 
 statements are given for what they are worth; that the 
 point is an important one will be at once recognised by 
 those who use this solvent largely in the analysis of 
 india-rubber goods. Ether, chloroform, carbon tetra¬ 
 chloride, turpentine, carbon bi-sulphide, petroleum spirit, 
 and benzene, and its homologues found in coal tar 
 naphtha, dissolve rubber readily, though only the two last- 
 named have any regular application in the manufacture of 
 india-rubber goods. The term solution is not a particularly 
 good one in this connection. It implies, in technical circles, 
 a viscous mass resulting from the swelling up of the rubber 
 in the solvent. As a colloid substance, distinct from what 
 is crystalline, it cannot be said to form true solutions, but 
 as we are discussing technical matters the common designa¬ 
 tion will be adhered to. Lack of volatility, extreme 
 volatility and consequent danger from fire, or the item of 
 expense are the main causes which have militated against 
 the adoption of solvents other than those derived from coal 
 tar or petroleum, the first employment of which by Macin¬ 
 tosh gave rise, as we saw in the first chapter, to the 
 establishment of the rubber industry. Mention ought not to 
 be omitted of the partial use of shale spirit as a solvent; this 
 is a product of the paraffin shale industry of Scotland, and 
 differs chemically from the coal tar and petroleum naphthas. 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 6 ' 
 
 These solvents find their principal application in the water¬ 
 proof branch, and special reference to them will be found 
 in another chapter. A very important property of india- 
 rubber, and one which hardly needs mention, is its 
 elasticity. It possesses this property to a much greater 
 degree than any other known substance. 
 
 Some scientific authors prefer to use the term distensi- 
 bility for that of elasticity, saying that the general use of 
 the latter by the rubber manufacturers and the public 
 arises from a misconception of facts. They point out that 
 the hardest steel is more perfectly elastic than a piece of 
 india-rubber. This may be strictly true and capable of 
 experimental demonstration, but at this time of day it 
 seems hopeless to expect that any reformed procedure in 
 this respect would he supported by the public, however the 
 manufacturers might come to regard it. It is proposed, 
 therefore, to use the expression “ elasticity ” in this 
 volume. 
 
 Action of Heat and Cold upon India-rubber .—At tem¬ 
 peratures below the freezing point india-rubber loses its 
 elasticity, becoming quite rigid, and indeed on immersion 
 in liquid air it becomes as brittle as glass. 
 
 At higher temperatures it becomes increasingly soft and 
 plastic until, at a point which varies according to the quality 
 of the rubber, it melts into a sticky mass which cannot again 
 assume the form and characteristics of the original sub¬ 
 stance. The temperature at which it begins to melt may 
 he put .at about 350° F., and after 400° F. it passes 
 into the condition of an oil. On destructive distillation 
 it yields a series of oils first investigated by Himly, Bov- 
 chardat and Greville Williams. The product of this 
 
 f 2 
 
68 
 
 INDIA-RUBBER. 
 
 distillation finds considerable reference in old treatises on 
 india-rubber, but although it has been mentioned as suitable 
 for many applications, it does not appear to have ever come 
 into regular use, and it must be looked upon merely as of 
 scientific interest. Some years ago the author prepared a 
 quantity by distillation in an iron retort fitted with a con¬ 
 densing arrangement. A considerable amount of charcoal 
 was left in the retort, which was finally heated to dull redness. 
 The crude distillate was redistilled into several fractions, 
 the lightest of which was of a pale lemon colour and had a 
 pleasant ethereal smell. Samples of these oils were tried 
 for purposes for which they had been recommended, but 
 in all cases the results were unsatisfactory. What has been 
 termed caoutchouc oil, used in the German army as a rust 
 preventative, is a solution of rubber in linseed oil, and is, 
 therefore, quite a different substance from the true oil of 
 caoutchouc, the pure distillation product. 
 
 Reverting to the effect of low temperatures upon india- 
 rubber, reference may be made to an erroneous statement 
 to be met with in some of our text-books on physics. It is 
 to this effect:—“ India-rubber, unlike the great majority of 
 substances, contracts when it is heated.” That there must 
 be something wrong about this is evident to the practical 
 man who is familiar with the expansion of india-rubber 
 goods when being vulcanized in moulds, and the explanation 
 of the anomaly is to be found in the omission of the writers 
 to use the qualifying adjective stretched. The fact is that 
 rubber in a normal condition expands on heating, but if it 
 is distended and then exposed to heat it certainly does con¬ 
 tract. This was demonstrated by Tyndall, who used a tube 
 of vulcanized rubber stretched to three times its length. 
 
CHEMICAL AND PHYSICAL PEOPEETIES. 
 
 69 
 
 Another example of this is seen by taking a thin strip of 
 rubber cut from a Para “ biscuit,” and stretching it out. 
 It will remain in this elongated condition for any length of 
 time, provided it is not warmed. If, however, it is merely 
 placed in the hollow of the hand, it will commence to 
 wriggle about and contract to its original dimensions. On 
 again being heated it will expand in the ordinary course. 
 Rubber in many of its manufactured forms is under tension ; 
 this is notably the case with fine cut sheet, and when this is 
 subjected to what is known as “ shrinking ” in the course 
 of the manufacture of certain goods, the result attained is 
 contraction in one dimension, and expansion in another. 
 Thus a piece of cut sheet rubber measuring 788 square 
 inches showed after five minutes “ shrinking ” on the steam 
 chest a superficies of 776 square inches when it had cooled 
 down. To leave this point and to pass on to another 
 of some scientific interest, it was noted by Lord Kelvin, 
 more than forty years ago, that rubber becomes hot 
 when stretched instead of becoming cooler, after the 
 manner of metals. Some experiments on this subject 
 were also published by Joule in the Philosophical Maga¬ 
 zine for 1857. This action can be readily observed by 
 stretching a piece of rubber on the bulb of a delicate 
 thermometer. 
 
 The specific heat of india-rubber has been determined by 
 the author and W. W. Haldane Gee, 1 and found to be ’48, 
 the same as for turpentine. 
 
 The thermal conductivity of rubber compared with some 
 other substances is here given, the figures representing 
 units of heat transmitted per square foot per hour by a plate 
 1 Proc. Man. Lit. and Phil. Soc., 1891. 
 
70 
 
 INDIA-RUBBER, 
 
 1 inch thick, the two surfaces differing in temperature by 
 
 1° F. The figures are due to Peclet. 
 
 
 Copper .... 
 
 . 515 
 
 Iron ..... 
 
 . 233 
 
 Marble .... 
 
 . 28 
 
 Glass..... 
 
 . 6 
 
 Oak ..... 
 
 . 1-7 
 
 India-rubber 
 
 . 1-37 
 
 Blotting-paper . 
 
 •27 
 
 Thus it will be seen that when vulcanizing in iron moulds 
 the heat will be transmitted through the iron and the rubber 
 
 in the ratio of 233 to 1*37, i.e., 170 
 
 times more quickly 
 
 through the iron than through the rubber. 
 
 The Diffusion of Gases through Rubber. —The fact that 
 india-rubber is capable of absorbing gases in its pores was 
 
 announced in 1831 by Dr. Mitchell, 
 
 of Philadelphia, his 
 
 experiments showing that those gases which were most 
 easily liquefied by pressure penetrated into the rubber the 
 
 most readily. Taking ammonia as 
 following table :— 
 
 unity, he gave the 
 
 Equal volume of gases. 
 
 Time. 
 
 Ammonia .... 
 
 1 min. 
 
 Sulphuretted hydrogen . 
 
 21 „ 
 
 Cyanogen .... 
 
 3J „ 
 
 Carbonic acid .... 
 
 „ 
 
 Nitrous oxide .... 
 
 61 „ 
 
 Olefiant gas .... 
 
 28 „ 
 
 Hydrogen .... 
 
 371 „ 
 
 Oxygen ..... 
 
 1 hr. 53 min. 
 
 Carbonic oxide 
 
 2 „ 40 „ 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 71 
 
 In 1867 the matter was closely studied by Graham, 
 Master of the Mint, in the course of his researches on 
 colloids, and he came to the conclusion that the passage of 
 gases through rubber could not be ascribed to simple gaseous 
 diffusion, but must be a case of liquid diffusion, the lique¬ 
 faction of the gases taking place in the pores of the rubber. 
 Of ordinary gases he found carbonic acid to penetrate the 
 most quickly, and he gave the following table with this gas 
 as unity. 
 
 Name of gas. Time ratio of diffusion. 
 
 Carbonic acid . . . • -1 
 
 Hydrogen . . . . • . 2‘47 
 
 Oxygen ...... 5*816 
 
 Marsh gas ...... 6*826 
 
 Air.H-850 
 
 Carbonic oxide ..... 12*203 
 Nitrogen ...... 13*585 
 
 Thus it will take thirteen and a half times as long for a 
 certain volume of nitrogen gas to pass through a film of 
 rubber as it does for the same volume of carbonic acid. 
 
 As far as the rubber manufacture is concerned, the sig¬ 
 nificance of these figures may he considered as limited to 
 the hollow ball branch, both ammonium carbonate and air 
 under pressure being used to bring about inflation. That 
 diffusion is continually going on may be demonstrated by 
 thoroughly washing a lawn-tennis ball and suspending it 
 in a sealed jar containing some Nessler solution—a delicate 
 test for ammonia—when the brown discolouration indica¬ 
 tive of ammonia will be seen after a short time. 
 
 Action of Alkalies and Acids. —Caustic alkalies, as would 
 
72 
 
 INDIA-RUBBER. 
 
 be expected in the case of a hydrocarbon, have no appreci¬ 
 able effect upon rubber, though where there is resin present, it 
 is dissolved to some extent. Neither have dilute hydrochloric 
 or sulphuric acids any action, though concentrated sulphuric 
 acid acts upon it energetically. 
 
 Nitric acid acts upon it in even very dilute solution in the 
 course of time with the formation of nitro-resinous bodies. 
 If the oxidation is carried far enough, the whole of the 
 rubber can be converted into oxalic and carbonic acids. In 
 some work the author did on this subject in 1891, 1 there was 
 obtained by the slow oxidation of pure sheet rubber 
 with dilute nitric acid a yellow body which gave on 
 analysis:— 
 
 
 Per cent. 
 
 Carbon 
 
 . 50-50 
 
 Hydrogen . 
 
 . 6-18 
 
 Oxygen 
 
 . 87-94 
 
 Nitrogen 
 
 . 5-48 
 
 
 100-00 
 
 At that time other matters being more pressing, the 
 investigation was dropped. Since then, however, a con¬ 
 siderable amount of work has been done by Harries, Weber, 
 and others, and the existence of definite nitro derivatives 
 has been established. 
 
 Much the same progress has to be reported with the 
 halogen derivatives, the first definite chlorine and bromine 
 compound having been prepared by Gladstone and Hibbert 
 in 1888, though it is interesting to note that a process for 
 preparing white rubber solution by passing chlorine into a 
 
 1 Proc. Man. Lit. and Phil. Soc., 1891. 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 73 
 
 solution of rubber in chloroform was described by Hurtzig 
 about thirty years ago. 
 
 The Action of Oxygen .—Of more general interest and 
 importance is the action of oxygen upon india-rubber, as 
 it is to this element that the decay of india-rubber goods 
 is mostly attributable. Attention seems to have been first 
 called to the subject by Spiller, 1 who found that rubber 
 which had decayed on exposure to the air contained a 
 quantity of a resin containing 27 per cent, of oxygen. 
 Later on, Burghardt 2 stated that besides this resin another 
 oxidation product, insoluble in alcohol and unsaponifiable 
 by alkalies was produced by atmospheric oxidation. In 
 1889 the author ( loc . cit.) pointed out that these oxidation 
 products differed considerably from the resins naturally 
 occurring in the different commercial brands of rubber, the 
 oxygen contents of these latter being from 10 to 14 per 
 cent. 
 
 Besins are not attractive bodies for the chemist to work 
 upon, and the labourers in this particular field have been 
 few. There is certainly room for further research into 
 details, although the main facts as far as the trade is 
 concerned may be considered established. As a result of 
 the work which has been done, it may be taken that 
 oxygen in the presence of the actinic rays is decidedly 
 injurious, and that the more the india-rubber is protected 
 from the light the longer will its life be. Further, the 
 more the rubber is “ worked” on the washing roller or in the 
 masticator, the greater is its tendency to oxidation. Opposite 
 views have been expressed on this point, but it would seem 
 
 1 Jour. Chem. Soc. [2] iii. 44. 
 
 2 Jour. Soc. Chem. Ind., 1883. 
 
74 
 
 INDIA-RUBBER. 
 
 that they are founded on unsatisfactory data. Burghardt 
 ( loc . cit.) gives a series of analyses of elastic thread showing 
 the increasing oxidation that takes place with time. 
 Though these figures undoubtedly are representative of 
 what goes on, it is surely incorrect to say that normal thread 
 contains no oxygen at all. The late Dr. Gladstone informed 
 the author that he found oxygen to the amount of 2 or B 
 per cent, in all his analyses of raw rubber, and the work 
 of more recent investigators all goes to confirm this. It 
 has been rather generally supposed that vulcanized rubber 
 is more sensitive to the insidious action of air and light 
 than is the unvulcanized; hut this has been controverted 
 by Weber, whose experiments certainly support his con¬ 
 tention as far as they go. There is plenty of proof, however, 
 that raw unmanufactured rubber has a much longer life 
 than the vulcanized rubber. Some of the samples of raw 
 Para rubber in Kew Museum must be now over sixty years 
 old, and the author lias a specimen in his possession 
 guaranteed to be forty-live years old and still quite sound. 
 This is in the form of drawn-out thread, and it has been 
 exposed to air all the time, though shielded from sunlight. 
 
 With regard to vulcanized rubber, evidence is wanting of 
 anything like such longevity. In the face of this experience 
 then, the statement that unvulcanized rubber is more 
 readily oxidised by atmospheric agency than is the 
 vulcanized substance must be taken with some reservation, 
 and with due regard to all the particulars involved. It is 
 evident that as regards liability to decay we must distinguish 
 between raw rubber as it comes from Brazil and un¬ 
 vulcanized rubber which has gone through the factory 
 processes of washing and drying. If we add to these 
 
CHEMICAL AND PHYSICAL PROPERTIES. 75 
 
 rubber which has been properly vulcanized by the aid of 
 sulphur and heat we have three distinct substances, and 
 the liability of each to oxidation or decay will depend very 
 largely upon the conditions under which the oxidation 
 takes place. Hence the exhortation as to caution in 
 accepting as axiomatic with regard to raw or vulcanized 
 rubber generally, what has been stated by this or that 
 observer as the result of special experiments. On the 
 present occasion the subject cannot be gone into more 
 fully, and it will suffice to summarise the results of 
 experience by saying that vulcanized rubber goods have 
 only a certain life; this life in the case of goods which are 
 not exposed to heat or friction depends to a considerable 
 extent upon exposure to the actinic rays—the less the 
 exposure, the longer the life. Wherever possible, then, 
 rubber articles when not in use should be stored in a cool, 
 dark place. This statement invites a special word of 
 warning to those dealers who, in order to attract the 
 attention of the passer-by, expose their goods in the shop 
 windows to the strong sunlight. Of course, there are 
 obvious difficulties in directing the public gaze to what is 
 stored in a dark cellar, but all the same it seems advisable 
 to draw attention to the risks involved in the ordinary 
 procedure, and, as for the rest, well, the shopkeepers must 
 be left to work out their own salvation. 
 
 Vulcanized rubber goods which are undergoing oxidation 
 have quite a distinct odour from those which are sound, and 
 this odour increases in power as the resinification proceeds. 
 In the case of thin coatings of compound rubber, such as are 
 to be seen in military ground sheets, the different stages of 
 oxidation can be seen in the gradual change to a plastic 
 
76 
 
 INDIA-RUBBEB, 
 
 substance which sticks to the fingers and on to a final 
 product which may be easily powdered. At this stage the 
 rubber is of no use to anybody, not even the waste rubber 
 merchant, with whose proceedings we shall be concerned 
 in a subsequent chapter. After seeing the above the 
 enquiring reader may be inclined to ask whether some 
 protective coating could not be applied to the rubber so as 
 to safeguard it against the insidious attacks of oxygen. 
 The answer to this is that various means have been 
 proposed but have resulted in nothing. If rubber had a 
 rigid surface the difficulty would probably not be great, but 
 seeing that elasticity is a prominent feature in most goods, 
 there is of course a pronounced tendency for a protective 
 coating to crack off when the rubber is under pressure or 
 tension. All the same, it cannot be said that the subject 
 has received that meed of attention which it would seem 
 to merit, and it is not desired to discourage further efforts, 
 although in regard to this matter it is not at all certain 
 that the discoverer of the elixir which is to indefinitely 
 prolong the life of rubber goods would be received with 
 acclamation by the manufacturers or by those who are 
 interested in india-rubber plantations. Besides the brown 
 resin, resulting from oxidation, decayed rubber always 
 contains 5 to 10 per cent, of water. From what has been 
 said as to the action of oxygen, it follows almost as a matter 
 of course that ozone has a strongly destructive action upon 
 rubber. 
 
 The Action of Grease vpon Rubber .—Users of rubber 
 goods, especially motor car owners, have been pretty 
 generally made aware of the fact that grease or oil is 
 injurious to rubber. Although the fatty oils, such as palm 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 1 7 
 
 oil, may be considered the most injurious, yet almost any 
 oil or fat is dangerous in that it softens the rubber and 
 partially dissolves it to form a sticky mass. In a general 
 way it may be stated that the damage done by oil is 
 directly proportional to the thickness of the rubber, con¬ 
 siderations of subsidiary, though not unimportant influence, 
 having relation to temperature and the general conditions 
 of exposure to sunlight. Those who have only heard of oil 
 as an enemy in connection with rubber may be surprised 
 to learn that it is a regular constituent of some classes of 
 goods, the heavy petroleum oil being most commonly 
 employed, though fatty oils are also used in this con¬ 
 nection. The injurious action of oil upon films of rubber 
 came into prominent notice about thirty years ago in 
 connection with the waterproofing of woollen cloths. Oil 
 is regularly used in the weaving process, and the decay of 
 a good deal of waterproofed cloth was traced to the presence 
 of this oil which sometimes amounted to 4 or 5 per cent. 
 Precautionary measures were then adopted, and it became 
 customary for waterproofers to test their cloths and reject 
 any which showed over 2 per cent, of oily extract. At the 
 present time such testing is but rarely resorted to because 
 those firms who make a speciality of textures for water¬ 
 proofing purposes guarantee that all their woollen cloths 
 have been scoured until practically free from oil. For 
 another reason the subject is of less importance than it 
 used to be, and this is because the cold curing process as 
 generally used twenty years ago has been succeeded by the 
 Dry Heat process and the rubber is not so likely to be 
 damaged by the presence of a small amount of fatty matter. 
 The action of oil upon rubber has been studied in detail 
 
78 
 
 INDIA-RUBBER. 
 
 by Thomson, 1 who experimented with elastic thread and 
 found that sperm tallow and neatsfoot oils at 100° E. 
 completely dissolved the rubber after some months, while 
 cotton seed oil, olive oil, cod liver and seal oils only caused 
 it to swell up, and that the only oil which had practically 
 no action was castor oil. Thomson’s experiments, though 
 of some scientific interest, were carried out under conditions 
 quite foreign to those which rubber goods are subjected to 
 in practice, and from the very contradictory statements which 
 have been published regarding the action of fatty matters 
 on vulcanized rubber, especially as to whether or no they 
 facilitate oxidation, it is clear that further work in this 
 direction is needed. No statements, then, of a positive 
 nature will be made here. All the same it is advisable in 
 the light of experience not to allow rubber goods to come 
 in contact with oil, as in many cases it may be expected 
 to prove decidedly injurious. 
 
 The Action of Copper upon India-rubber. —Copper, either 
 in the form of the metal, the oxides, or the soluble salts, has a 
 decidedly injurious action upon rubber. This was first pointed 
 out some twenty-five years ago by Burghardt, and subsequent 
 inxestigations have shown that the alarm note first sounded 
 was by no means unjustified. Indeed it has been proved 
 that exceedingly small quantities of copper or its salts, much 
 smaller than was originally supposed, have the power to 
 cause the decay of certain rubber goods. Exactly what the 
 action is has not been entirely cleared up, but in the case of 
 metallic copper it has been plausibly attributed to oxidation 
 induced by the dissolved oxygen in the copper. The 
 deleterious action of the copper is much accelerated in the 
 1 Jour. Soc. Chem. Ind,, December, 1885. 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 19 
 
 presence of grease, or in fact any substance capable of acting 
 as a solvent. Weber lias drawn attention to the fact that 
 goods cured by Dry Heat, that is, speaking more particularly 
 of textures, are less likely to be damaged by copper than 
 those which are cold cured. In the former case the insoluble 
 sulphide of copper is formed, and in the latter soluble salts. 
 In the light of the experience of insulated rubber cable 
 manufacturers this statement of Weber’s regarding the 
 innocuous behaviour of sulphide of copper must not be read 
 too closely. In the cable manufacture it is the universal 
 rule to coat the copper wire with tin in order to prevent the 
 sulphur from attacking the copper to form copper sulphide. 
 With regard to the rubber manufacture proper, the only 
 trouble experienced with copper has been in the water¬ 
 proofing branch and elastic webbing, the copper being found 
 associated with the black and brown dyes of certain fabrics. 
 Of course the quantities present are only very small and one 
 must be cautious in making comparisons with the cable 
 industry, where the amount of copper available for acting 
 on the rubber is very much larger. Still, whether the 
 copper sulphide is to be considered harmful or not, it is a 
 good rule to bar the presence of copper altogether, and at 
 the present time it is quite the exception to come across it 
 in any goods intended for use with rubber. As in the case 
 of grease, the manufacturers of textiles for the proofing trade 
 have arranged their dyeing procedure so as to obviate the 
 necessity of using copper salts, and trouble from this source 
 seems to be altogether a thing of the past. Any action which 
 other metals exert upon rubber is too trifling to call for any 
 notice and there does not seem to be any evidence of the inimical 
 action of chromium salts as has been stated to be the case. 
 
80 
 
 INDIA-EUBBE R. 
 
 India-rubber stands high as an insulator of electricity 
 and consequently has a wide application in the electric cable 
 manufacture. Its specific inductive capacity, otherwise known 
 as the electrostatic capacity and the dielectric constant, 
 may be taken as 2"22 for the pure substance, the varying 
 figures to be met with evidently having reference to 
 vulcanized and compounded rubbers. At the present time 
 it is not uncommon to come across insulating rubber con¬ 
 taining over 60 per cent, of mineral matter, and for these the 
 specific inductive capacity may be 4‘6 or even higher. 
 The same thing occurs with most insulating substances 
 which may vary in grade composition or degree of refine¬ 
 ment to a considerable extent. Unless, therefore, we have 
 some knowledge of these various and variable factors, any 
 figures relative to specific substances must not be read too 
 closely. As the most recent publication on the subject, 
 Abbott’s “ Transmission of Energy ” has been drawn upon 
 for the following table, dry air as the most perfect insulator 
 being taken as unity :— 
 
 Name of Material. 
 
 Air .... 
 Ordinary glass 
 Flint glass, extra dense 
 India-rubber . 
 
 Ebonite . 
 
 Gutta-percha . 
 
 Sulphur . 
 
 Shellac . 
 
 Paraffin . 
 
 Ozokerite 
 
 Specific Inductive 
 Capacity. 
 
 1 
 
 1- 90 to 8-013 
 6-55 to 10-10 
 
 2- 22 to 3-70 
 2-284 
 
 2-580 to 4-20 
 1-93 
 
 1-95 to 2-740 
 
 1- 98 to 2-00 
 
 2- 13 
 
CHEMICAL AND PHYSICAL PROPERTIES. 
 
 81 
 
 Another important electrical constant in connection with 
 light and power cables is the insulation resistance which is 
 expressed in terms of megohms per mile. This varies with 
 the temperature and also with the quality of the rubber. 
 Speaking generally, it has been shown that unvulcanized 
 rubber is superior to vulcanized, and that the effect of 
 compounding is to decrease the resistance. 
 
 A third electrical constant is the dielectric strength, and 
 some figures by Gray, showing the inferiority of rubber 
 compared with mica, are here given. 
 
 Material. 
 
 Maximum Dielectric 
 Strength in Kilowatts 
 per Centimetre. 
 
 Glass 
 
 285 
 
 Hard rubber . 
 
 538 
 
 Soft rubber 
 
 476 
 
 Mica 
 
 . 2,000 
 
 Micanite 
 
 . 4,000 
 
 I.R. 
 
 G 
 
CHAPTER IV. 
 
 VULCANIZATION. 
 
 It will be convenient at this juncture to say a few words 
 explanatory of vulcanization, the importance of which 
 process in the technology of our subject has already been 
 briefly alluded to in the first chapter. It was discovered by 
 Charles Goodyear, of Newhaven, United States, America, in 
 1839, after many years of experimenting, that rubber when 
 mixed with sulphur and then subjected to a temperature 
 above the melting point of the latter (239° F.), underwent 
 a remarkable transformation in its physical and chemical 
 properties. It was no longer soluble in the ordinary media, 
 such as turpentine, chloroform and naphtha, neither was it 
 influenced by such degrees of heat and cold as profoundly 
 affected ordinary rubber. Further, and more important 
 still, its elasticity was considerably increased. Such were 
 the main characteristics of the new body, and it is not 
 surprising that their importance led to instant recog¬ 
 nition on the part of others engaged in the rubber manu¬ 
 facture. Prominent among these was Hancock, who had 
 some small pieces of Goodyear’s rubber given to him by 
 Mr. Brockedon, a partner in Charles Macintosh & Co., in 
 the autumn of 1842. Hancock was in complete ignorance 
 of the means whereby Goodyear had effected his end, 
 nor did he have the samples analysed. Setting to work, 
 
VULCANIZATION. 
 
 83 
 
 however, with indomitable energy to imitate them, he 
 succeeded in so doing in 1843, and in 1844 took out liis 
 patent for the use of the sulphur bath. A propos of Good¬ 
 year’s discovery, the information comes on reliable authority 
 that the rubber contained white lead as well as sulphur, 
 and that Goodyear himself did not attach that degree of 
 importance to the sulphur which it was later demonstrated 
 by Hancock to possess. But be this so or not, it is clear 
 that to Goodyear belongs the first discovery of vulcanization. 
 Hancock, although deserving every credit for his rediscovery, 
 having the valuable incentive that what has been done once 
 can be done again. Though the point of actual priority of 
 discovery, however, may be considered settled, there can be 
 little doubt that its application to the trade generally 
 is due to Hancock rather than Goodyear, for very little 
 appears to have been done between 1838 and 1844. It was 
 soon recognised that Goodyear’s process of mixing the 
 sulphur intimately with the rubber, and then exposing the 
 mixture to heat, was of far more general applicability than 
 was Hancock’s method of putting the rubber in a bath of 
 molten sulphur. Still the latter had a considerable appli¬ 
 cation for certain purposes, and, contrary to what has been 
 stated by recent authors, it is still in regular use, in England 
 and France at all events. With regard to the term vulcani¬ 
 zation, this has been attributed to Goodyear by some authors. 
 It was Mr. Brockedon, however, who first suggested the name 
 of the deity of fire as appropriate in this connection. Vulcani¬ 
 zation is now a dictionary word in very general use in the 
 trade, though as applied to the cold process to be described 
 directly it is certainly objectionable, as embodying a con¬ 
 tradiction of terms. 
 
 g 2 
 
84 
 
 INDIA-RUBBER. 
 
 Sulphur was the substance used by the original investi¬ 
 gators to attain the desired end, and to this day the element 
 remains supreme for the purpose, despite the very numerous 
 attempts by subsequent investigators to effect its substitu¬ 
 tion. Exactly what the reaction is that takes place during 
 the vulcanization process cannot be said to he satisfactorily 
 settled yet, despite the attention which the topic has 
 received in recent years. Former writers talked glibly 
 about the production of a sulphide of caoutchouc, hut with¬ 
 out bringing forward any experimental evidence of their 
 assertions, and at the present day, the once widely-held 
 theory of a substitution compound—that is where one or 
 more atoms of hydrogen have been replaced by sulphur— 
 has been abandoned as untenable. Probably the theory 
 advanced by C. 0. Weber, to the effect that vulcanized 
 rubber is an addition product, is most correct. Taking the 
 india-rubber hydrocarbon as Ci 0 H lC , this would pre-suppose 
 the vulcanized rubber to be some multiple of C 10 H lfi S, but 
 the matter is of too abstruse a nature to warrant further 
 discussion here, and we may proceed to matters of more 
 practical import. It is generally supposed that not more 
 than 3 per cent, of sulphur is chemically combined with 
 the rubber, the remainder existing in the free condition in 
 the pores thereof. This figure, however, must not be read 
 too closely, recent research having shown that much depends 
 upon the details of the process. 1 As a rule, however, about 
 3 per cent, is found to be left in rubber which has been 
 subjected to a prolonged boiling in caustic soda solution 
 which dissolves out the free sulphur. The exact amount of 
 
 1 Weber has obtained a vulcanized rubber with 7 per cent, combined 
 sulphur. 
 
VULCANIZATION. 
 
 85 
 
 combined sulphur present does not affect, to any appreciable 
 degree the elasticity, though an excess of free sulphur must 
 in many cases be considered as injurious. Until recent 
 years, practically no attention had been paid to the scientific 
 side of vulcanization, and even now the absence of complete 
 harmony among the investigators in the results obtained, 
 renders it necessary to exhibit a certain reserve in putting 
 on record what amounts to no more than a working 
 hypothesis. 
 
 Properly vulcanized pure india-rubber will stretch to 
 seven times its length without breaking and return to its 
 original dimensions when released from stress, thus showing 
 a property possessed by no other known substance. This 
 statement refers, of course, to pure rubber and sulphur, and 
 not to heavily compounded rubber. 
 
 The advantages of vulcanization can hardly be over¬ 
 estimated, but it must also be recognised that vulcanized 
 rubber has only a limited life. Owing doubtless to the 
 presence of the sulphur, especially the free sulphur, it is 
 very prone to atmospheric oxidation, the rapidity of which 
 depends largely upon the conditions to which the goods 
 are subjected, as also upon their composition and mode 
 of manufacture. The phenomenon of an old macintosh as 
 stiff as a board, or of a rigid tobacco pouch are familiar 
 illustrations of this oxidation process. 
 
 Methods of Vulcanization. 
 
 There are two or three processes of vulcanization which 
 are in regular use, and a whole host that have been proposed 
 at one time or another and either never put into operation 
 at all, or only to a very partial extent, and subsequently 
 
86 
 
 INDIA-RUBBER. 
 
 discontinued. With regard to these latter, there seems no 
 object in taking more than passing notice of one or two of 
 the most prominent, those which are alive claiming our 
 best attention. 
 
 The usual method of incorporating the necessary sulphur 
 with the rubber is on the mixing rolls which are described 
 elsewhere. For this purpose, sublimed flowers of sulphur in 
 a fine state of sub-division and free from crystals and 
 sulphur acids are used. By the mixing process, the sulphur 
 is intimately incorporated with the rubber or rubber com¬ 
 pound as the case may be, and the “ mixing ” having been 
 made into the goods required has now to undergo the 
 heating process, for so far it has undergone no change, 
 being simply a mixture. The forms of vulcanizing plant 
 vary according to the nature of the goods, but in principle 
 they are all the same in that the rubber is raised to a 
 temperature varying from 265° F. to 285° F. for a greater or 
 less length of time, according to the special circumstances 
 and needs of each case. It will he more convenient to refer 
 to the particular forms of vulcanizing plant when dealing 
 with the goods for which they are chiefly used. 
 
 Another mode of mixing the sulphur with the rubber will 
 be instanced when we come to elastic thread and water¬ 
 proof textures. 
 
 A third method used only in the case of small articles 
 made of pure rubber, is what is known as the sulphur bath, 
 the form of apparatus originally used by Hancock in his 
 experiments. This is merely an iron pan in which brim¬ 
 stone is kept in a molten condition by means of a fire or a 
 steam jacket. The rubber when placed in the pan absorbs 
 a certain amount of the sulphur into its pores, turning a 
 
VULCANIZATION. 
 
 87 
 
 brown colour. Much the same result is obtained according 
 to Chapel and various other authors by Girard’s process in 
 which the goods are immersed into a hot solution of persul¬ 
 phide of potassium or sulphydrate of lime under pressure. 
 It is possible that this process is in use in France, but 
 the author could never get any satisfactory evidence of its 
 application anywhere, and much doubts whether it has ever 
 been used in Great Britain. 
 
 Parkes Process .—Another and quite distinct process of 
 vulcanization now claims attention, namely, that invented 
 by Parkes in 1846, and more appropriately known as the 
 “cold cure.” Compared with the sulphur and heat process 
 it is of distinctly limited application, as it is only suitable 
 for rubber in thin sheets. It consists in dipping the goods 
 into a mixture of bi-sulphide of carbon and chloride of 
 sulphur, generally 40 of the former to 1 of the latter. The 
 action takes place in the cold and is of very limited duration, 
 a few seconds being usually all that is required. The active 
 agent is the chloride of sulphur, the part played by the 
 mephitic liquid, bi-sulpliide of carbon, being merely that of 
 a solvent and a dilutant. It used to be thought that the 
 chlorine was the element which brought about the change, 
 but according to the researches of Weber it would seem that 
 the sulphur in this, as in the Goodyear process, is the 
 responsible agent, though both chlorine and sulphur 
 combine with the rubber to form addition products such as 
 may be expressed by the formula, CioHieSaC^- A danger 
 connected with this process is the development of free 
 hydrochloric acid arising from decomposition of the sulphur 
 chloride by moisture, and it is now customary to reduce 
 this source of trouble to a minimum, either by giving the 
 
88 
 
 INDIA-RUBBEE. 
 
 freshly vulcanized rubber a good washing or, where 
 this is not permissible, to expose it to the vapours of 
 ammonia. 
 
 That the use of this process is objectionable from a 
 hygienic standpoint is undeniable, the bi-sulphide of carbon 
 vapour having a very serious effect upon the health of those 
 subjected to its fumes. Under the clauses of the Factory 
 Acts passed in 1896, its application is now hedged round 
 with stringent regulations which cannot he considered at all 
 superfluous by those who know the havoc wrought in the 
 past, though they may possibly he described as unneces¬ 
 sarily irksome by those responsible for their due observance. 
 Moreover, now that continental countries have fallen into 
 line with England in this matter, the complaints which 
 were at first heard as to the serious effect on the particular 
 trade concerned, have quite lost their significance. At one 
 time this process was much more largely used, than is at 
 present the case, for the vulcanization of waterproof textures; 
 when, however, the Dry Heat method began to be largely 
 adopted in 1884, the cold curing with chloride of sulphur 
 fell largely into desuetude. A name in common use for 
 this process, it may be mentioned, is “sincaloring,” derived 
 from sine colore, though its derivation is not always 
 respected by those who employ it. It is sometimes 
 written “sincolor,” and the form “sinklor ” also is to be 
 met with. 
 
 Another method of vulcanizing with chloride of sulphur 
 should be mentioned, though it is not of wide application. 
 The goods, nearly always articles made from pure sheet 
 rubber, are hung up in wooden zinc-lined chambers with 
 tightly fitting doors. A small amount of chloride of sulphur 
 
VULCANIZATION. 
 
 89 
 
 is placed on a dish and evaporated by the heat of steam pipes 
 which are placed on the floor of the chamber. The acid 
 vapours are readily absorbed by the rubber, and when, 
 after the lapse of a certain time, the chambers are opened no 
 smell of chloride of sulphur can be perceived. Goods treated 
 in this way are really only surface cured, and, except for 
 special purposes, the vulcanization with heat and sulphur 
 gives a better and more durable article. 
 
 A year or two ago some stir was aroused by the announce¬ 
 ment from America of a process of electric vulcanizing, though 
 so far no practical developments have to be recorded. More¬ 
 over, as the only part which the electricity was to play 
 appeared to he in the capacity of a heating agent for vulcaniz¬ 
 ing goods containing sulphur, there is no new principle 
 involved, even supposing that it proved satisfactory in practice. 
 With regard to the Doughty process of vulcanizing in a short 
 time, at a high temperature, the case is different, as the 
 process has been largely adopted at the works of the 
 Dunlop Rubber Company, this firm having obtained sole 
 possession of the patents. Although the opinion was widely 
 held, a few years ago, that the use of temperatures as high 
 as 320° F. must inevitably prove destructive to the rubber, 
 this has certainly been falsified in the event. The process is 
 not adapted for rubber of any thickness, as it would burn 
 the outside before the interior was vulcanized, hut it is 
 largely used for cycle tyre covers by the Dunlop Company 
 at Birmingham, and also at their continental and Australian 
 works. The actual time of vulcanization is three minutes 
 at 175 lhs. pressure or 370° F., the whole process, including 
 putting in the tubes and taking them out, lasting only five 
 minutes. Moreover, the necessary shape is given to the 
 
90 
 
 INDIA-RUBBER. 
 
 cover during the vulcanizing. The possession of this patent 
 undoubtedly puts the Dunlop Company in a much stronger 
 position, as regards output, than is the case with their 
 competitors, who are restricted to older and more lengthy 
 methods. 
 
 Since the extension of the motor tyre business and the 
 general use of vulcanizing apparatus by repairers through¬ 
 out the country, considerable looseness has attached to the 
 way in which the term “vulcanization” is used. We have 
 seen that all the processes of vulcanizing, as carried on in 
 the india-rubber works, involve the use of sulphur or of 
 chloride of sulphur, and it is incorrect to talk of vulcanizing 
 where neither the ordinary hot nor cold processes are 
 employed. This, however, is done by not a few connected 
 with the tyre repairing trade in reference to specialities they 
 are desirous of bringing before the public eye. It certainly 
 seems desirable, in the interests of a clear understanding, that 
 processes of attachment, or of rejuvenation, should, when 
 carried out without the use of heat and sulphur in com¬ 
 bination or of the cold cure, be designated by some term 
 other than vulcanization. 
 
 In concluding this important topic it may be emphasised 
 that in whatever way the process of vulcanization is 
 carried out, it is at once the most important and the most 
 delicate which the factory manager has to control. The 
 results obtained are influenced not only by the amount of 
 sulphur present, the time and the temperature, but also to 
 some extent by the character of the rubber, and in the case 
 of compounds by their quantity and nature. It will be 
 seen at once that very considerable technical knowledge 
 is demanded for the control of an operation which, if 
 
VULCANIZATION. 
 
 91 
 
 unskilfully carried out, may easily lead to a loss of 
 hundreds if not thousands of pounds in a short time. 
 The difficulties of everyday work are not great when 
 established procedure has to be followed, variation in the 
 raw rubber being the only cause from which trouble may 
 arise. It is rather in the production of new classes of 
 goods and in the constant changing of the composi¬ 
 tion caused by alteration in the market price of the raw 
 material, and also in the constant demands for a cheaper 
 article that the ingenuity of the factory manager is severely 
 taxed. The premature end of many rubber goods has 
 frequently formed a fruitful source of speculation, and 
 although in such cases it is often a matter of the very 
 greatest difficulty to assign a cause, it is probable that 
 defects in vulcanization are as often as not the primary 
 source of trouble. 
 
 It may be taken as beyond cavil that excess of sulphur is 
 responsible for a good deal of trouble in mechanical goods 
 used for steam purposes. It has been mentioned on page 84 
 that only a comparatively small amount of sulphur, averag¬ 
 ing, say, 8 per cent., is chemically combined with the 
 rubber. A larger quantity than this, nearer in fact to 10 
 per cent, on the rubber by weight, is always used in practice, 
 as otherwise the vulcanization would take up too much 
 time. In some classes of goods, notably those consisting 
 of rubber and sulphur alone, or containing red sulphide of 
 antimony in addition, it is customary to immerse the 
 articles in a hot solution of caustic soda, in order to dis¬ 
 solve out the excess of sulphur. It has often been urged 
 against this procedure that it renders the rubber somewhat 
 porous and more susceptible therefore to atmospheric 
 
92 
 
 INDIA-RUBBER. 
 
 oxidation. That this objection has not much weight, 
 however, is conclusively shown by the use of the process 
 for the last fifty years by the foremost firms in the trade, 
 who have doubtless satisfied themselves of its economic 
 advantages. It is obvious that it cannot be used in the 
 case of thick or heavily compounded goods, and in these 
 the excess sulphur has perforce to remain, generally 
 showing itself after a short time on the surface as a white 
 efflorescence, to use a common, though perhaps not a 
 scientifically correct, term for the phenomenon. The 
 sulphur is at first in the colloidal or uncrystallized con¬ 
 dition, though after a time it assumes the crystalline state. 
 The objections to this efflorescence are sentimental rather 
 than rational, and though in many cases the removal of 
 the sulphur is demanded by the retailer because it is a bar 
 to the sale of the goods, there are still many and notable 
 instances where no such desulphurization is called for or 
 practised, and where the goods give every satisfaction in 
 their specific applications. Although in England caustic 
 soda is almost universally used for desulphurizing, on the 
 Continent potash in the form of the American black ash is 
 much in favour, although it is more expensive. This is 
 because of the smoother surface it imparts to the rubber. 
 A rather troublesome feature with regard to this desulphuriz¬ 
 ing process is the difficulty attending the disposal of the 
 waste liquor. This consists of a number of sodium salts, 
 of which the sulphide predominates, and there is always 
 some free caustic left. In the case of elastic thread there 
 is also a good deal of shellac in solution. Nowadays urban 
 and river authorities exercise more supervision over trade 
 effluents than was the case in the past, and trouble has 
 
VULCANIZATION. 
 
 93 
 
 arisen on more than one occasion with regard to this 
 caustic liquor. Like a good many other trade effluents it 
 can he rendered practically innocuous without any great 
 expense or trouble being incurred, though the idea which 
 has taken root in some minds as to its being utilised to 
 advantage ought, it would seem, to be dismissed. The 
 author went pretty fully into the matter some years ago, 
 and came to the conclusion that it could not be utilised to 
 advantage. The quantities available at any particular 
 time are insufficient for any continuous manufacture of 
 precipitated sulphur or sodium salts, and then there is the 
 organic impurity due to the shellac. Barring trials which 
 have been made of it as a detergent in a workhouse, it 
 does not seem to have ever had any practical application. 
 
 So much for the vulcanizing processes in regular and 
 extensive use.. With regard to the various other bodies 
 which have been proposed as vulcanizing agents, the oxides 
 of nitrogen are much too dangerous, and have never found 
 any application, and much the same may be said with 
 regard to chlorine and bromine. Iodine in the form of 
 metallic iodides has had some use; Fawsitt, and also 
 Weber, having taken out patents in connection with them 
 for the dry heat of waterproof textures. As, however, these 
 processes seem to be not now in use anywhere there is 
 little attraction in dilating on them. There remains, 
 however, a sort of vulcanizing process known by the name 
 of acidizing, which dates back for many years and is still 
 in partial use. The active agent is liypochlorous acid in 
 dilute solution, obtained by the addition of a mineral acid 
 to bleaching powder. Naturally no penetration of the 
 rubber can occur in an aqueous solution, so the effect is 
 
94 
 
 INDIA-RUBBER 
 
 merely a superficial hardening. Washing in a weak 
 ammonia solution serves to remove any excess of acid, 
 and the process, at any rate, has the result of destroying 
 the adhesiveness of pure rubber without rendering the use 
 of French chalk necessary. 
 
CHAPTER Y. 
 
 INDIA-RUBBER PLANTATIONS. 
 
 The subject of cultivated rubber is attracting so much 
 attention at the present time that it has been thought 
 desirable to put all references to it in one chapter, so as to be 
 easy of access to those whose chief interest in rubber lies in its 
 future supply. The idea of supplementing the supplies of 
 native rubber with the product of plantations is by no means 
 a new one, initiative having been taken in India as far back 
 as 1860, owing presumably to the decreased yield of Assam 
 rubber from destructive methods of collection. It was not, 
 however, until 1872 that the subject was recognised as of 
 real importance, and in that year James Collins, an Edin¬ 
 burgh botanist, was instructed by the India Office to draw 
 up a report concerning the rubber trees of America, and to 
 ascertain whether they could be grown in India. In 1875, 
 Robert Cross, of Liverpool, in concert with C. R. Markham, 
 of Assam, was sent to Panama to collect seeds and cuttings 
 of the Castilloa tree. He was also sent by the India Office 
 the following year to Para to collect information about the 
 trees yielding the Para and Ceara rubbers. His official 
 report shows that he met with formidable difficulties in the 
 course of his undertaking, but he succeeded in his main 
 object. The seeds and cuttings which he obtained in his 
 journeys were duly sown and planted at Ivew, and in due 
 
96 
 
 INDIA-RUBBER 
 
 course dispersed over various botanical gardens in India and 
 the Colonies, where, in many instances, they are now flourish¬ 
 ing as trees. It would take too long to follow step by step the 
 history of the movement thus inaugurated, but the matter 
 continued to claim the close attention of Colonial Governors 
 and curators of botanical gardens with varying degrees of 
 success, and the work done can claim to be the foundation 
 of what is now to be seen in the large number of existing 
 plantations, from many of which rubber is now being 
 regularly dispatched to the European markets. It is only 
 a very few years ago that prominent American rubber 
 manufacturers pooh-poohed the idea of putting money into 
 rubber plantations; there was no object they said in 
 paying for what a bountiful nature would perform free of 
 cost. To-day, however, this tone seems to have been 
 changed, and there is a general disposition among practical 
 men in America, as well as Europe, to regard rubber 
 planting if not as a necessity, at any rate as a desirable 
 branch of economic botany, and likely to be a profitable one 
 withal. 
 
 That acclimatised rubber trees can be successfully grown 
 where the climate approximates to that of their original 
 habitat is now an assured fact, and that they can he grown 
 at a cost admitting of large profits is also now beyond 
 dispute, but these are not all the factors which come up 
 for consideration. Perhaps the question which is asked 
 more frequently than any other by prospective investors 
 in a new company, is whether there is any likelihood of 
 the production from the new sources being so great as to 
 bring prices down to an unremunerative level. Now this is 
 a point on which it is almost impossible to speak with 
 
INDIA-RUBBER PLANTATIONS. 
 
 97 
 
 precision, and the author instead of committing himself to any 
 categorical statement of his prognostications will limit himself 
 to the more cautious step of pointing out the main factors 
 which must be taken into consideration. In the first place, 
 with regard to the demand for rubber in the arts there can be 
 no room for doubt that the remarkable increase in the demand 
 witnessed in recent years will continue, even if not in the 
 same ratio of progress ; it may also be taken for granted that 
 the output from America and Africa will not show a corre¬ 
 sponding rate of increase, although the increase may be 
 expected to be steady and maintained. As the figures for 
 the exports of Para rubber sorts show a yearly rise since the 
 commencement of the industry, and as the rubber has always 
 found a ready sale at constantly increasing prices, we have 
 here an adumbration of success for the plantation product. 
 It is evident then that the present high price is due not 
 to any indications of exhaustion in the crop, but to the inter¬ 
 actions of the ordinary laws of supply and demand. It must 
 not be overlooked by the zealous advocates of plantations in 
 Ceylon and the Straits Settlements, that far from South 
 America showing signs of depletion, there are vast quantities 
 of rubber trees in Bolivia, Peru, and Columbia, which are at 
 present untapped owing to scarcity of labour and lack of 
 transport facilities. It is in this labour question that the 
 planters have the advantage over the exploiters of the forest 
 product; labour is not only cheap, but also, at any rate in 
 Ceylon, it is abundant, and any failure in this respect need 
 not come under consideration. The future for the planta¬ 
 tions, then, more particularly as regards the payment of sub¬ 
 stantial dividends, would seem to depend a good deal upon the 
 utilisation or the non-utilisation of the latent stores of rubber 
 
 i. it. 
 
 H 
 
98 
 
 INDIA-RUBBER. 
 
 known to exist in South America. In the face of the state¬ 
 ments made by planters as to their actual costs of production 
 (Is. to Is. 6 d. per lb.) it is clear that they would witness a 
 considerable fall from present prices with equanimity, sup¬ 
 posing that no disaster of an untoward nature overtakes them. 
 
 With regard, however, to the somewhat confident predic¬ 
 tion of a planter, made in the course of conversation with 
 the author, to the effect that we shall witness a parallel case 
 to that which happened with the quinine industry in South 
 America, the land of its birth, a discrepancy must be pointed 
 out. The quinine plantations in Java and elsewhere have 
 killed the old South American business certainly, but only 
 because they produced an identical article at a much lower 
 cost. Is this the case with the plantation rubber industry 
 in Ceylon and the Straits ? As far as things have gone up 
 to the present it is not; expert opinion on plantation Para 
 rubber being unanimous that it is deficient in strength com¬ 
 pared with the Brazilian product. To some readers this 
 may seem a somewhat startling statement, and inconsistent 
 with the fact that the plantation rubber fetches the highest 
 price in the market. This apparent inconsistency, however, 
 may be easily explained. The higher price fetched by the 
 plantation rubber is due to its greater content bulk for bulk 
 of rubber. In other words, it is exported in a practically 
 dry and clean condition, hardly losing 1 per cent, in 
 washing, while the Brazilian “ biscuits ” always contain 
 water, and traces of other matter, yielding a loss of from 
 15 to 20 per cent. When due allowance is made for 
 this loss it will be found that the latter rubber is con¬ 
 sidered by the manufacturers the more valuable. So far, 
 of course, very little plantation rubber has come upon the 
 
INDIA-RUBBER PLANTATIONS. 
 
 99 
 
 market compared with the imports from Brazil, and it has 
 been used for purposes such as solution making, where its 
 cleanliness is an attraction, and its deficiency of nerve no 
 disadvantage; but it has not yet replaced Para rubber in 
 its most important applications, such as cut sheet and elastic 
 thread. 
 
 This statement refers, of course, only to the time of 
 writing, and it is quite conceivable that improvements in 
 the methods of collection and coagulation may be made in 
 the near future, which will put quite a different aspect upon 
 affairs. In the meantime, however, what has just been 
 said indicates that Brazil’s sun has by no means set, nor is 
 there any possibility of such an event until rubber of the 
 same intrinsic merit is plentifully produced elsewhere. 
 
 Although at the present time planting in Ceylon is being 
 confined almost exclusively to the Para tree ( Hevea 
 Braziliensis) , it was the Ceara tree ( Manihot glaziovii) 
 which was at first chiefly grown. Very little success, how¬ 
 ever, was attained by the majority of tea planters, probably, 
 to judge by reports of present growers, because of 
 inexperience in methods of procedure. By way of com¬ 
 pleteness a few details of the present methods followed in 
 Ceylon are appended, and those who wish to go further into 
 the subject are advised to study the files of the India-rubber 
 World and the India-rubber Journal, where original up-to- 
 date articles are of frequent occurrence. Mention should 
 also be made, in this connection, of the books by W. H. 
 Johnson 1 and Wright, 2 though it should not be overlooked 
 
 1 “The Cultivation and Preparation of Para Rubber,” W. H. 
 Johnson, F.L.S. Crosby Lockwood & Son, 1904. 
 
 •2 << p ara Rubber,” Wright, 1906. Ferguson, Colombo. 
 
 H 2 
 
100 . 
 
 INDIA-RUBBER. 
 
 that events in this new industry have succeeded one another 
 very rapidly, and methods but a year or two old have already 
 become obsolete. 
 
 As a rule, the young trees which are tapped are at least 
 five years old. With regard to the yield of rubber this is so 
 variously stated by different planters that evidently a 
 number of factors have to he taken into consideration, and 
 it does not seem advisable to pass on figures of which the 
 details are not available. The coagulation of the latex is 
 carried out by diluting it with four times its hulk of cold 
 water, and to every gallon of the diluted liquor one drachm 
 of acetic acid is added. The liquor is then introduced into 
 what is known as the Mitchie Golledge machine, in which it 
 is churned until the coagulated rubber separates as a white 
 spongy mass. This is removed, passed through rollers, 
 sliced into shreds, and when dried in a current of hot air forms 
 the “worm” rubber now becoming familiar in the London 
 market. It will be noticed that no smoking of the rubber 
 takes place as in Brazil, though a special apparatus for 
 smoking has been designed, and is in partial use. In the 
 preparation of the Ceylon biscuit rubber the diluted latex is 
 allowed to stand in shallow vessels until coagulation takes 
 place, the rubber being then passed through rollers and 
 dried on shelves in a warm room. Very similar methods 
 are followed in the Straits Settlements, and the Para rubber 
 from that district has the same qualities and defects as the 
 product of Ceylon. And, indeed, the characteristic lack of 
 tensile strength, coupled with freedom from moisture and 
 impurities, have been observed since the first plantation 
 Para rubber was seen in Europe, as far as information is 
 available. This was the case, at any rate, in a sample from 
 
INDIA-RUBBER PLANTATIONS. 
 
 101 
 
 Mergui, India, which the author examined fifteen years ago. 
 As to the cause of the lack of strength, whether it is due to 
 the tree being tapped while immature, or to the rubber not 
 being smoked, or to various other causes which have been 
 suggested at hap-hazard as possible solutions, nothing can 
 be put forward as yet with apy degree of confidence. The 
 matter, however, is receiving close attention at the hands of 
 experts, and authoritative information ought to be forth¬ 
 coming before long. Weber certainly seetns to discount 
 the idea that smoking the rubber will do all that is required, 
 and expresses himself emphatically in favour of mechanical 
 coagulation. This opinion awaits corroboration. A matter 
 which has received some attention already, and deserves to 
 receive more, is concerned with the nature of the soil. 
 Planters of experience imagine that there may be trouble in 
 store for Ceylon when the young trees attain adolescence, 
 and their roots strike deeper down below the alluvial. They 
 base their concern in this matter on what has happened 
 with other crops cultivated in Central America. Although 
 there seems no reason whatever to adopt a pessimistic tone 
 with regard to this matter, as the conjecture is based on the 
 dubious foundation of analogy alone, yet it seems important 
 enough to warrant attention at the hands of those responsible 
 for the future welfare of the plantations. 
 
 To such an extent have the prospectuses of Rubber 
 Plantation Companies in Ceylon and the Straits and 
 Malaya loomed recently in the public eye, that it is not 
 surprising to find a general notion that the new industry 
 is practically confined to these districts. By way of dis¬ 
 possessing the uninformed reader of this idea the following 
 table, which is taken from the Ceylon Observer of July or 
 
102 
 
 INDIA-RUBBER. 
 
 August, 1905, will be found useful. The figures, it should 
 be said, only claim to be approximate, and should not be 
 read too closety. The estimate gives about 150,000 acres 
 
 under cultivation, and this no doubt has now considerably 
 
 increased. 
 
 
 Notes. 
 
 Ceylon .... 
 
 40,000 
 
 Mostly Para. 
 
 Malay Peninsula 
 
 38,000 
 
 do. 
 
 Borneo .... 
 
 1,500 
 
 Experimental Para. 
 
 Java .... 
 
 6,000 
 
 do. 
 
 India and Burmah. 
 
 8,000 
 
 Young Para. 
 
 Mexico .... 
 
 10,000 
 
 Castilloa. 
 
 Brazil .... 
 
 5,000 \ 
 
 
 Venezuela 
 
 3,000 
 
 Just planted. 
 
 Ecuador 
 
 2,000) 
 
 
 Panama 
 
 300 
 
 Castilloa. 
 
 Best of Central America 
 
 2,000 
 
 Just planted. 
 
 Natal . . . . 
 
 50 
 
 Experimental. 
 
 Rhodesia 
 
 100 
 
 do. 
 
 Best of Africa 
 
 33,000 
 
 Mostly vines. 
 
 Tobago and West Indies 
 
 1,000 
 
 Castilloa. 
 
 
 149,950 
 
 
 The above notes have been inserted by the author. 
 
 From some of these districts cultivated rubber has been 
 on the market for years. It is stated on good authority 
 that there are cultivated Castilloa trees in Nicaragua over 
 forty-five years old which have been tapped for thirty-five 
 years. A good deal of the rubber planting in Nicaragua 
 resulted in failure and it seems clear from present successes 
 
INDIA-BUBBEB PLANTATIONS. 
 
 103 
 
 that only certain parts of the country are suited to the 
 purpose. 
 
 Mexican rubber plantations have not proved attractive to 
 the British investor since the collapse of India-rubber 
 (Mexico) Ld.—an English concern—nor can it be said of all 
 the numerous enterprises of this sort which have been 
 started in Mexico that they will bear close inspection. At 
 the same time the cultivation of the Castilloa tree is 
 making good progress, and those concerns whose formation 
 will stand a close scrutiny, should prove profitable invest¬ 
 ments. The first consignment of plantation rubber was 
 shipped to the United States in 1901, and recent reports 
 point to steady progress. It is impossible to analyse the 
 above table throughout, but a mere glance at it will serve 
 to show that Ceylon and Malaysia have by no means a 
 monopoly of the business. 
 
CHAPTER VI. 
 
 INDIA-RUBBER SUBSTITUTES. 
 
 Coincident with the establishment of the rubber manu¬ 
 facturing industry has to be noted the efforts of inventors 
 to discover or prepare a substitute. Despite, however, 
 strenuous application to this end it can he said without fear 
 of contradiction that up to the present no real substitute 
 has been discovered. That is if we use the term in its 
 correct sense of substituting rubber entirely. The partial 
 success which has been attained has reference only to the 
 displacement of some part of the rubber in various goods 
 by bodies which reduce the cost at the expense of the 
 quality. Not until we get some substance which, on 
 admixture with rubber cheapens it, without at the same 
 time reducing its quality, can it truthfully be contended 
 that real progress towards the desired end has been attained. 
 The substitutes which have so far been used have really 
 no status beyond that of cheapening ingredients, and 
 it is undeniable that, in the earlier days of the industry, 
 when goods were rarely if ever subjected to chemical 
 analysis, substitutes paraded to a great extent as rubber 
 to the pecuniary advantage of unscrupulous manufacturers. 
 He would be a bold man, however, who contended that such 
 a practice was common to-day. Owing to close competition, 
 those goods in which substitutes are used are sold at their 
 
INDIA-RUBBER SUBSTITUTES. 
 
 105 
 
 true value; grasping buyers may possibly be shocked to 
 hear that they are not buying pure rubber, but it is really 
 their own fault. Goods made of the purest rubber can 
 always be obtained from the manufacturers by those who 
 are willing to pay the price, and speaking in a general way 
 of the trade, such goods as are highly compounded are pro¬ 
 duced often under protest to satisfy the purchaser’s ideas as 
 to price. Under these circumstances we join issue with 
 those who refer to the use of substitutes generally as an act 
 of adulteration. It would seem that the cases where this 
 contention would fairly hold are not at all numerous; 
 cases, that is, where goods containing substitutes are sold at 
 the price of pure rubber. Of course there are exceptions to 
 this dictum, but it may nevertheless be taken as generally 
 true. 
 
 It would be a vain task to enumerate the heterogeneous 
 list of bodies simple and compound which at one time or 
 another have been confidently proposed as rubber substi¬ 
 tutes. The curious on this point will find a good deal to 
 interest them in H. C. Pearson’s book. It is sufficient to 
 say that the great bulk of the inventions, so called, have 
 benefited no one except those who are professionally con¬ 
 cerned with patents. Invention in this direction, however, 
 shows persistent vitality, and a glance at the patent lists of 
 to-day suggests that practically every known substance is 
 being drawn upon and as often as not for the second time. 
 It hardly seems superfluous to offer a word or two of advice 
 to would-be tillers in this apparently attractive field; firstly, 
 acquaint yourself thoroughly with the physical properties of 
 raw rubber ; secondly, get a practical trial of the substance 
 made in a rubber works before spending money on patents. 
 
INDIA-RUBBER. 
 
 106 
 
 All this talk about rubber substitutes, notwithstanding, 
 it becomes of interest to consider whether the discovery 
 when made, is likely to be of such supposed value. If there 
 was any real danger of a rubber famine the value of 
 an efficient substitute would undoubtedly be immense. 
 So far, however, from any danger of a famine we can 
 face the future with complacency. As already pointed 
 out in the last chapter, the rubber to be expected in 
 the future from plantations will be produced at about 
 Is. per lb. It will, no doubt, be a long time before the 
 growers sell it at any such figure, but should any threatened 
 opposition arise from a substitute, it may be taken that the 
 growers will forego the bulk of their profits for a time at 
 least, and put good rubber on the market at or about Is. 
 per lb. This means that the substitute, if it is to realise 
 the fortune its introducers will undoubtedly expect, will have 
 to be made at about 6d. to 9d. per lb. It is difficult to see 
 where the materials are to come from to render manufacture 
 possible at this price, and it is evident that the synthetic 
 rubber prepared by Professor Tilden from terpenes cannot 
 have any commercial significance. It would seem then 
 that, whatever may have been the case in the past, the 
 present prospects of wealth for the discoverer of a rubber 
 substitute are largely illusory. This does not mean that 
 there is no room for improvement in such bodies as are 
 in use at the present time or for the invention of new ones 
 to take their place. Such bodies will continue to offer 
 scope for the inventor, and may be expected to bring him 
 in a fair reward for successful labour. They are not, 
 however, real substitutes, and do not come within the 
 limits of a discussion on rubber substitutes proper. The 
 
INDIA-RUBBER SUBSTITUTES. 
 
 107 
 
 main defect in all the bodies which have been used 
 or suggested as substitutes is lack of elasticity. So 
 far the production of this property has quite baffled the 
 investigator, and it follows, therefore, that no substitute 
 has deposed rubber from its high position in cases where 
 elasticity is a requisite. On the other hand, it will be 
 apparent that where elasticity is not really required as in the 
 case of waterproof goods, door mats, etc., substitutes in 
 reasonable proportion may have a legitimate use in reducing 
 cost, without at the same time impairing efficiency to any 
 great extent. Moreover, their use instead of mineral 
 matter enables the specific gravity to be kept low and the 
 suppleness to be maintained. 
 
 We may now proceed from the general to the particular 
 and consider the rubber substitutes which are in regular 
 use. These are by no means numerous, in fact, broadly 
 speaking, there are only two which need claim more than 
 passing notice. The first is known in the trade as white 
 substitute, and the other variously as brown, black or 
 French substitute. Exactly when these bodies began to be 
 used in the rubber trade it is not easy to say, but apparently 
 they were known even if they had no regular application 
 long before they attracted the attention of the rubber manu¬ 
 facturer. What is known with certainty, is that forty years 
 ago the white substitute was being made in the neighbour¬ 
 hood of Manchester by two firms, who for many years 
 had a monopoly of the business exporting both to the 
 Continent and to America. In those days the process was 
 more or less a secret one, and no doubt the absence of 
 competition made the business a decidedly profitable one. 
 The case is very different to-day, when a general knowledge 
 
108 
 
 INDIA-RUBBER. 
 
 of the reaction involved, has enabled close competition to 
 spring up. Although the actual process of manufacture is 
 a short and simple one and may be carried out successfully, 
 by one possessing no knowledge of chemistry, yet the 
 chemical reactions involved are extremely complicated, and 
 it cannot be said, despite the original work carried out by 
 Ulzer and Horn, 1 and later by Henriques, 3 that we under¬ 
 stand clearly all the details of the reactions which take 
 place. It is not proposed here to go into details or to 
 discuss controversial points, and it will suffice to say that 
 the various white substitutes are glycerides, whose fatty 
 acids contain chlorine and sulphur as addition products. 
 The general process of manufacture is to stir a certain 
 quantity of chloride of sulphur—a very penetrating and 
 objectionable liquid—into linseed, rape or other unsaturated 
 fatty oil mixed with petroleum spirit. After a few minutes’ 
 stirring, during which time a considerable rise of tempera¬ 
 ture takes place, the oil begins to thicken and to be converted 
 into a yellowish, more or less elastic body. The particular 
 oil used and the quality and amount of sulphur mono- 
 cliloride added, are matters which affect the final product to 
 some extent. Such details are somewhat jealously guarded 
 by the manufacturers as trade secrets, and there is no 
 intention here to draw aside the veil that hides them 
 from the public eye. With regard to the generalities, 
 however, it may be said that the oil most commonly used 
 at the present time is refined colza, there being a decided 
 difference in the stability of the products obtained from 
 various oils. The presence of free acid was a constant 
 
 1 Jahresber d. Chem. Technol., 1890, p. 1177. 
 
 2 Chem. Zeit, 1893, p. 707. 
 
INDIA-RUBBER SUBSTITUTES. 
 
 109 
 
 source of trouble to the rubber manufacturers in earlier 
 times, but the substitute makers of to-day have learnt how 
 to produce a neutral product. What is also important 
 is that the liability to decomposition has been greatly 
 lessened. The author can now testify to samples having- 
 withstood the action of sunlight for four years without 
 showing signs of decomposition. It used to be the common 
 thing for white substitute exposed in a bottle to sunlight to 
 turn into an oily mass in a few weeks. As an industry, 
 the substitute manufacture has the drawback of being a 
 very disagreeable one for those closely concerned, owing to 
 the fumes of the chloride of sulphur, and many are the 
 stories which could be related of the troubles in which the 
 pioneers of the manufacture found themselves involved. 
 This was owing, it must be confessed, a good deal to the 
 indifference with which they regarded the rights and 
 convenience of their neighbours. As hinted already, the 
 competition of the business is such that the man with 
 ten pounds capital who bought a wooden tub, some oil, 
 and a bottle of chloride of sulphur and set up manufacturing- 
 under a railway arch, has been compelled to desist by 
 a concatenation of adverse circumstances. The more 
 substantial firms in whose hands the business now lies, 
 and with whom it forms only a branch of a more general 
 trade, have adopted means whereby the nuisance arising 
 from the fumes has been largely done away with. 
 
 Passing on now to the dark or French substitute, it 
 would seem that this was the first in the field. For a long 
 time, certain French firms had a practical monopoly of it 
 as the actual process of manufacture was not understood in 
 other countries. This cannot, however, be said to-day, and 
 
110 
 
 INDIA-RUBBER. 
 
 practically all the firms who make the white variety make 
 the dark also with varying degrees of success. The manu¬ 
 facture differs from that of the white substitute, in that 
 sulphur takes the place of the chloride of sulphur, and the 
 reaction takes place at a high temperature. In the process, 
 a vegetable oil is heated to about 200°C., and a certain 
 proportion of flowers of sulphur is added, the mixture 
 being regularly stirred. In due course the oil thickens 
 considerably, and at a certain point it is poured out into a 
 shallow receptacle where it quickly solidifies. Sometimes 
 it is allowed to solidify in the boiling pot, the source of heat 
 being removed. Although apparently a simple process 
 close attention to detail is necessary in order to ensure 
 success and to obtain a uniform product. Though the 
 fumes given off in this case are not so irritating as in 
 the chloride process, being free from mineral acid, yet 
 they are by no means pleasant, as sulphuretted hydrogen 
 is generally present. To some people the vapours of hot 
 oil are decidedly objectionable, and it is not surprising to 
 hear of manufacturers who, after commencing the business, 
 gave it up in order to make a living in pleasanter paths. 
 The brown substitute is a more stable body than the white, 
 and it is somewhat surprising that it has not been used to 
 a greater extent in preference to the latter. No doubt its 
 colour is against it in the case of goods where transparency 
 is desired ; but this objection apart, its resistance to decom¬ 
 position under vulcanizing temperatures makes it the more 
 desirable substance to use for the generality of goods. 
 Some writers have made it appear that the general custom 
 in the rubber manufacture has been to use the dark for 
 steam-cured goods and the white for textures, etc., which 
 
INDIA - EUBBEE SUBSTITUTES. 
 
 Ill 
 
 are cold-cured. This, however, has been by no means the 
 case, the white substitute having been used extensively in 
 steam-cured goods. No doubt the hydrochloric acid formed 
 during vulcanization was taken up by metallic oxides or 
 other absorbents present, thus having its tendency to 
 mischief neutralised. All the same there is little that can 
 be urged in favour of the use of white instead of dark 
 substitute in steam-cured goods, and the science which is 
 slowly superseding the empiricism of the past in the rubber 
 manufacture will doubtless cause the use of the white body 
 to be limited to cold-cured goods. The market price of 
 these substitutes varies from 3 d. to Id. per lb., the lower 
 figure having been rendered possible during recent years 
 by the use of maize oil, which is largely produced in 
 America. A cheapening of the original product has also 
 been effected by the use of “blown oils”—that is, rape or 
 cotton seed oil which has been partially oxidised by air. 
 These latter oils require less chloride of sulphur for their 
 conversion, but the contention made for the product that 
 it is superior to the ordinary substitute, certainly does not 
 meet with general acceptance in the rubber factories. 
 
 These substitutes, it should be said, are by no means 
 homogeneous bodies, and a proximate analysis showing oil, 
 sulphur and chlorine has little value. In the ordinary 
 solvents of india-rubber they merely swell up, only a 
 small portion going into solution. They have, however, 
 the special property of going completely into solution 
 when mixed with rubber—that is, as far as rubber can 
 be said to form a solution. Owing to this property, 
 these substitutes have found a large, and it must be 
 added regrettably large, use in the manufacture of cheap 
 
112 
 
 INDIA-KUBBER. 
 
 waterproofs, the amount of rubber present being practically 
 limited to the minimum necessary to get the substitute into 
 solution. 
 
 Some analytical figures are here appended, giving at a 
 glance the general constitution of these bodies :— 
 
 
 White Substitute. 
 
 Dark Substitute. 
 
 Oily matters 
 
 . 88-2 
 
 88 
 
 Sulphur . 
 
 6-6 
 
 12 
 
 Chlorine . 
 
 5-2 
 
 — 
 
 
 100-0 
 
 100 
 
 Both substitutes give varying amounts of oily extract to 
 solvents, such as ether and petroleum spirit, and the dark 
 often contains a good deal of its sulphur in the free 
 condition. 
 
 The rubber substitutes just referred to represent a class 
 of bodies which are intended for use in the rubber manu¬ 
 facture as. a raw material to replace the pure rubber. 
 There remains, however, a class of substances sometimes 
 called rubber substitutes which are complete in themselves, 
 and are made into finished articles to compete with rubber 
 goods on the market. These are either proprietary or 
 patented substances credited, as a rule, with the possession 
 of advantages over rubber, either in the matter of price or 
 of specific attributes, such as the power to resist oil or 
 oxidation. A glance at the history of such bodies in 
 general shows that the failures to come up to expectation 
 largely outnumber the recognised successes, and that there 
 are really very few cases where infancy has evolved into 
 robust adolescence and where longevity can be predicted with 
 confidence. In several cases where a patent was taken out 
 
INDIA-RUBBER SUBSTITUTES. 
 
 113 
 
 for a weird-looking mixture of substances said to be capable 
 of replacing rubber, it was found necessary to use a certain 
 amount of rubber as well, in order to produce saleable 
 goods, though the addition was not announced from the 
 house-tops. In other instances, where patented compounds 
 were primarily destined as substitutes for rubber, they have 
 found a wide sphere of utility, not in replacing rubber, but 
 other substances, notably leather. The true leather sub¬ 
 stitute has not yet been found, and probably never will be, 
 but compounds made from oxidised and nitrated oils have 
 made considerable progress in recent years in replacing 
 leather for certain classes of upholstery work. Thus we 
 have pegamoid, a nitrated cellulose product; pluviusin, 
 an oxidised oil body; velvril, a nitrated oil, and two or 
 three other leather substitutes which have proved their 
 worth for certain purposes. Their claims to be con¬ 
 sidered rubber substitutes, where they have been advanced, 
 cannot be seriously considered ; though, of course, for certain 
 purposes, as, for instance, in belting or bed-sheeting, they 
 may enter into competition with rubber. With regard to 
 viscose, the cellulose product made by Cross and Bevan by 
 the action of carbon bi-sulphide on a solution of wood-pulp 
 in caustic soda, Weber spoke very highly of its possibilities 
 as a rubber substitute. Nothing, however, seems to have 
 come of it, though it had a trial in several rubber factories. 
 
 It has already been pointed out that the main defect 
 of so-called rubber substitutes is their lack of elasticity. 
 This remark applies very generally to the bodies we are now 
 considering, and therefore it is not surprising that the 
 greatest success has been scored in cases where elasticity is 
 of little importance, as, for instance, in waterproof clothing 
 
 I.R. 
 
 I 
 
114 
 
 INDIA-RUBBEE. 
 
 and electric insulation. Thus the diatrine insulation 
 brought out by G. Heyl-Dia, and now the property of 
 Messrs. W. T. Glover and Co., occupies a high place as a 
 substitute for rubber insulation, and much the same thing 
 can he said of the vulcanized bitumen so largely used by 
 Messrs. Callender and Co. as an insulating material. Other 
 bodies largely used for insulating purposes in America are 
 kerite and okonite; the latter, by the way, having been 
 manufactured on a large scale near Manchester a dozen 
 years ago. If, however, we attempt to apply these bodies, 
 so useful in their particular spheres, to the variety of pur¬ 
 poses for which rubber is in requisition, their deficiencies 
 as rubber substitutes become at once apparent. 1 An 
 interesting substance, known as vulcanized fibre, has a con¬ 
 siderable use for steam purposes, as it is Unaffected by the 
 temperatures which would rapidly prove fatal to vulcanized 
 rubber. Another rubber-like compound, which for mechanical 
 purposes has largely replaced both vulcanized rubber and 
 leather, is known as dermatine. This is made by the 
 Dermatine Company of London on the lines of a patent 
 taken out by Zingler in 1884, though it is understood that 
 the original process has been considerably modified as the 
 result of experience. Various gums and chemicals enter 
 into its composition, the product when vulcanized having 
 much the appearance of rubber, though it would seem to 
 have undoubted advantages over the latter for such purposes 
 as hydraulic cup and ram-rings. 
 
 1 As okonite contains rubber it must be excluded from this general 
 observation. 
 
CHAPTER VII. 
 
 RECLAIMED RUBBER. 
 
 Under the various names of recovered rubber, reclaimed 
 rubber, rubber shoddy, Pongo rubber, etc., rubber goods 
 which have done service in their several spheres of utility 
 again come before the manufacturer’s notice. The trade 
 of reclaiming old rubber so as to fit it for re-use has been 
 in existence for a long time ; but in recent years it has 
 shown considerable expansion, a fact which may be ascribed 
 to two principal causes: improvement in the methods of 
 production, and the extended market owing to the high 
 price of raw rubber. To effect the devulcanization of old 
 rubber or of vulcanized scrap,, a regular product of the 
 rubber factory, is a problem which has long been of the 
 first importance. It cannot, however, be said that we are 
 really in any better position than we were fifty years ago 
 as regards the main object to be achieved. If the term 
 recovery is used as synonymous with devulcanization, it 
 cannot seriously be contended by any rubber reclaimer that 
 the desired goal has been attained. All the brands of 
 reclaimed rubber on the market contain sulphur, and the 
 most that can be said for them is that the original vulcan¬ 
 ized rubber, from being an intractable substance, has, by the 
 method of reclaiming employed, been rendered suitable for 
 use again ; that is, to a limited extent for certain purposes. 
 
 i 2 
 
116 
 
 INDIA-RUBBER, 
 
 It must not be thought, however, that such reclaimed 
 rubber has anything approaching the characteristics 
 and value of new rubber. This is not at all the case, and 
 there are numbers of goods in which it could not possibly 
 be used with beneficial results. This statement will no 
 doubt be challenged by the reclaimers, or, at any rate, by 
 some of them, but the author derives support from the fact 
 of the general unwillingness there is in the rubber trade to 
 acknowledge the use of reclaimed rubber. This anxiety to 
 avoid publicity can hardly be urged as testimony to its 
 virtues, nor can the clause in the Government specifications, 
 stating that no reclaimed rubber is to be used, be taken 
 in any more favourable light. The use of exaggerated 
 language is perhaps permissible in trade circles, but it does 
 not seem to have been shown that any reclaimed rubber is 
 equal to new rubber of the best quality, though it must be 
 admitted that so great have been the improvements 
 effected by individual firms in recent years, that much 
 reclaimed rubber is produced which is decidedly superior to 
 raw rubber of low grade. 
 
 The reclaiming of waste rubber has long been a much 
 more elaborate business in the United States than has been 
 the case in Europe. The principal raw material of the 
 American trade is the discarded golosh—an article which 
 is manufactured and utilised to a much greater extent in 
 America than in England. The collection of the old ones 
 has long been systematised, and quantities find their way 
 to the large reclaiming factories in the States. What the 
 proportion of goloshes collected is to those manufactured is 
 a matter that would probably be difficult to determine, but 
 it is certainly a large proportion. Of course the Americans 
 
RECLAIMED RUBBER. 
 
 117 
 
 use other old rubber stock as well, buying it in large 
 quantities, not only in their own country, but also in 
 Europe. In England and other European countries re¬ 
 claiming has been carried out on a much more modest 
 scale, and it is only quite recently that the collection of the 
 old rubber goods has been organised into a regular industry. 
 Time was when old rubber could be got by the reclaimer 
 for the asking, or for the trouble of carting it away; but 
 now things are very different, and practically all the waste 
 rubber has to be paid for at full rates. The Government 
 departments—especially the post-office—the railway com¬ 
 panies, and other large users now regularly sell their old 
 rubber either by tender or by auction, and smaller users of 
 mechanical rubber goods have recently got into the habit 
 of stipulating with the suppliers that they shall be allowed 
 so much for the old material. In fact, the field is now 
 well covered. 
 
 Perhaps the most important fact in connection with 
 the waste rubber industry in Europe is the recent estab¬ 
 lishment at Litherland, near Liverpool, of a reclaiming 
 factory by Americans. Business is here carried on in a 
 huge factory on American lines, the waste rubber being 
 obtained from Europe generally. It is not surprising that, 
 in mining parlance, the mill at first got ahead of the mine’; 
 in other words, that a difficulty was found in getting 
 enough scrap rubber to keep the place in full work. This 
 difficulty, it is understood, has now been overcome. In 
 contradistinction to what obtains in the States goloshes are 
 not the principal raw product at Liverpool, motor and 
 cycle tyres largely taking their place. All classes of rubber 
 goods do not lend themselves with equal facility to the 
 
118 
 
 INDIA-RUBBER. 
 
 reclaiming process, and for a long time there was no 
 market at all for goods which contained an excess of 
 canvas or metal. Armoured hose, for instance, has long 
 been looked at askance by reclaimers as involving too much 
 labour in its treatment. With regard to this body it is 
 worthy of mention that a special machine has recently 
 been patented by R. R. Gubbins, by which the metal of 
 internally and externally armoured hose can be expe¬ 
 ditiously removed from the rubber at a very trifling cost 
 compared with the hand labour which is generally used. 
 Many rubber goods, notably cycle and motor tyres, con¬ 
 tain a considerable proportion of canvas, which has to be 
 removed before the reclaiming process is entered upon. 
 In many cases the separation of the rubber from canvas 
 and metal is carried out by the reclaimers, though there 
 are many waste rubber dealers who carry out this opera¬ 
 tion themselves, selling the scrap rubber to the reclaimers 
 or to rubber manufacturers direct, many of the latter now 
 having reclaiming plant of their own. As the Gubbins 
 patent machine is now in regular operation, it will be of 
 interest to give a brief description of it. In principle it is 
 a plain and straightforward application of the well-known 
 slitting rolls used in the iron trade for slitting a long sheet 
 of iron into nail rods. The india-rubber tubing or inser¬ 
 tion sheet is divided by the action of the rolls into a 
 number of narrow strips almost like belt laces. In this 
 form the fragments of metal are easily removed, and the 
 canvas is quite as readily destroyed by acid or alkaline 
 solvents, as when the rubber has been ground into crumb 
 on rollers after the method usually followed. The con¬ 
 struction and working of the machine are characterised by 
 
RECLAIMED RUBBER, 
 
 119 
 
 simplicity, and it should go a long way to render profitable 
 the reclaiming of rubber from armoured hose. 
 
 Another patented process for treating waste rubber con¬ 
 taining canvas deserves particular mention, as it bids fair 
 to eclipse the older methods in which chemicals are 
 employed. It is due to Penther, a German, though the 
 patent rights for the world have recently passed into the 
 hands of a company, who have put up a factory at Leyland, 
 in Lancashire, to work the process on a large scale. It 
 would be difficult to describe the machine well without 
 diagrams, for which space cannot be afforded, but in prin¬ 
 ciple it consists of a series of knives and air blasts. By the 
 former the rubber is reduced to fragments, and the canvas 
 particles are removed by the air. The canvas now in a 
 state of fluff, quite free from rubber, commands a ready 
 sale for felt making and other purposes, at a price sufficient 
 to pay the running expenses of the machine. In this 
 process then the trouble and expense of the ordinary 
 methods of dissolving the textile material in acid or alkali 
 are obviated, and its success seems assured, though at this 
 early stage of its adoption a little reserve is necessary in 
 casting its horoscope. 
 
 The mystery which at one time hedged round the opera¬ 
 tions of the reclaiming factory has now been largely 
 dispelled, and there exist hardly any secrets in the various 
 processes, except in points of detail. The processes may be 
 roughly classified as mechanical and chemical. In the 
 former case the old rubber is ground on rollers, similar to 
 those already referred to as mixing rollers, to a fine powder, 
 which, after being run over magnets to extract particles of 
 iron, is subjected to a current of air, whereby the particles 
 
120 
 
 INDIA-RUBBER. 
 
 of canvas are removed. The rubber is then, according to 
 general American practice, heated in hot air stoves to a 
 high temperature, with the addition of a certain quantity 
 of rosin oil or petroleum, by which treatment it becomes 
 to some extent devulcanized, and capable of being rolled 
 into homogeneous plastic sheets. In its broad outlines this 
 is the process as adopted in the preparation of mechanically 
 reclaimed rubbers. In the chemical or acid process—the 
 patents in connection with which occupied the American 
 Law Courts for so long a few years ago—the fibrous matter 
 is destroyed by mineral acid, sulphuric and hydrochloric 
 being generally used. This form of treatment will be 
 referred to again later. Other and more modern processes 
 comprise a combination of mechanical and chemical treat¬ 
 ment. Space does not permit of reference to the varied 
 and very numerous patents which have been taken out in 
 connection with perfecting the reclaiming process, but two 
 systems, from their interesting nature and the large scale 
 on which they are at present being carried on, may con¬ 
 veniently have extended reference. At the works of the 
 North-Western Rubber Company, already referred to as 
 being established at Litherland, near Liverpool, the alkali 
 system patented by A. H. Marks, of the Diamond 
 Rubber Company, Akron, Ohio, U.S.A., is in use. A 
 summary of the process is as followsThe ground-up 
 waste rubber passes by means of elevators and conveyor 
 belts to a number of oscillating sieves. Here the coarse 
 material is separated from the fine, and goes back to 
 the rollers for re-grinding. The fine material, which has 
 passed the sieves, is taken by a spiral elevator to the 
 devulcanizers, which are large iron vessels steam-jacketed 
 
EECLAIMED EUBBEE. 
 
 121 
 
 and capable of standing a high pressure. There are several 
 of these vessels, each of which has a capacity of about 
 two and a half tons of rubber, and in them the most 
 important part of the process takes place. This consists 
 of extraction of the free sulphur with caustic soda solution, 
 and at the same time of the solution of the particles of 
 fibrous matter. When this reaction is over the rubber is 
 thoroughly washed to free it from alkali, and is then dried 
 on specially constructed screens heated by steam coils, a 
 current of air under pressure being used to expedite the 
 removal of moisture. When thoroughly dry it is sheeted 
 on rollers, without it is stated the use of any oil. Of 
 course there are details of importance which this synopsis 
 of the process does not touch, but enough has been 
 said to satisfy the curiosity of the general reader. It 
 is safe to say that had this been a British factory it would 
 not have been possible to say as much. It must not 
 be supposed that the large output of reclaimed rubber 
 from the Litlierland Works finds its sole market in England ; 
 as a matter of fact, business is done all over Europe, and 
 the site of the factory being where it is is due to considera¬ 
 tions of general convenience. We may now pass to the 
 second reclaiming factory it is proposed to refer to, this 
 being one of those rare instances in Europe where the 
 management does not shun a certain amount of publicity. 
 This concern is situated at Copenhagen, and has the 
 euphonious title of Dansk Afvulkaniserings Aktieselskabet, 
 which done into homely English means the Danish Devul- 
 canizing Company, Limited. Here the chemical part of the 
 process is based on the patents taken out by Albert 
 Theilgaard, though the process in its entirety is by no means 
 
122 
 
 INDIA-RUBBER. 
 
 revealed in the Patent Office files. The main point to be 
 observed is that neither acid nor alkali is used to effect the 
 solution of the sulphur and fibrous matter, neutral solutions 
 of sulphites being employed as the solvent for the sulphur, 
 while the fibre is removed by certain neutral salts, the exact 
 nature of which is not disclosed by the management. It is 
 stated that the sheeting of the chemically treated rubber is 
 effected without the admixture of any oil or cheap resinous 
 rubber, and if so the process must be considered a highly 
 satisfactory one. The resulting rubber cannot, of course, 
 be either acid or alkaline, and freedom from the oil, which is 
 such a distinctive feature of American practice, naturally 
 brings up the rubber content. In saying this much it must 
 not be supposed that reclaimed rubbers prepared by the other 
 methods are liable to contain acid or alkali. The author’s 
 own experience goes to show that, at any rate where reliable 
 firms are concerned, such reclaimed rubbers put on the 
 market are quite neutral as a result of the careful washing 
 process to which they have been subjected prior to sheeting. 
 
 Mention has been made of recovery processes in which the 
 fibre has been blown out by an air current, and where it 
 has been dissolved by alkaline solutions. It may also be 
 removed by acids, some reclaimers using a diluted solution 
 of vitriol for this purpose. In this case it is inevitable that 
 a certain quantity of the mineral matter in compounded 
 rubbers should go into solution, but the loss of weight thus 
 caused is not great in practice, because the process is pretty 
 generally confined to cases where the rubber is not ground 
 up, and where the canvas, as in the case of railway-brake 
 hose, has been mostly separated by mechanical means. The 
 chief objection to the acid process is the liability of the 
 
RECLAIMED RUBBER. 
 
 123 
 
 rubber to retain acid in its pores. A thorough washing in 
 water, or better, dilute alkali solution, is necessitated in order 
 to remove the acid. As a rule this work is carried out 
 satisfactorily, and one very rarely hears complaints nowa¬ 
 days of acidity. If prophecy is permissible it would appear 
 that the alkali chemical processes, already referred to in 
 detail, are likely to supplant the acid treatment when the 
 details on which their success depends become more gener¬ 
 ally known, or when the patents under which they find 
 protection become void by the lapse of time. Where the 
 acid process finds its principal application in England is in 
 the recovery of waterproof cuttings. In proportion to the 
 rubber present the amount of textile material is large, and 
 the process usually adopted with reclaimers is to boil the 
 cuttings—which are largely obtained as waste from the 
 waterproof cutting rooms—in hydrochloric acid solution. 
 The cotton and wool are thoroughly rotted by the acid, and 
 are removed from the rubber by washing on rollers in a 
 stream of water, the washing being continued until the acid 
 is entirely removed. This rubber, especially that from 
 goods which have been cold-cured, is only lightly vulcanized, 
 and fetches a good price. With the decay of the macintosh 
 industry, however, supplies of the cuttings have been 
 difficult to obtain, and the amount of this class of reclaimed 
 rubber has consequently diminished. It may, not unnatu¬ 
 rally, be asked whether this process of destroying the textile 
 material is not unnecessary and wasteful. At first sight it 
 may appear so, but it is a fact that of the various patents 
 and processes which had for their object the recovery both 
 of the rubber and the cloth, none, to the best of the author’s 
 knowledge, have proved successful. This from a variety of 
 
124 
 
 INDIA-RUBBER, 
 
 reasons, some of which may be briefly mentioned. Leaving 
 out of account the diminution in the production of the raw 
 material, we have the important fact that no discrimination 
 is made, either by the waterproof manufacturers or the 
 waste rubber dealers, between the cotton and the wool 
 cuttings. It may be taken that only the latter offer any 
 attraction as far as the recovery of the fabric is concerned, 
 the cotton having practically no market value. If wool or 
 union cuttings could be had in sufficient quantity, and free 
 from those consisting of cotton alone, there seems no 
 reason why some at any rate of the processes which have 
 been proposed should not prove financial successes. The 
 recovered wool has a ready market in the woollen districts 
 of West Yorkshire, though it has to be entirely free from 
 rubber. Among those who have recently worked in this 
 field may be mentioned R. E. Gubbins, in whose patent of 
 1900 claim is made for the use of hot petroleum oil as a 
 solvent, the softened rubber being squeezed off the cloth 
 during passage through rollers. In the patent of Robinson 
 Brothers and Clift the higher boiling coal-tar bases, obtained 
 as a bye-product in the manufacture of pyridine, are used 
 as the solvent. On heating the cuttings in this liquid the 
 rubber goes completely into solution, and may be precipi¬ 
 tated by benzol. The woollen fabric, after washing with 
 sulphuric acid to remove the residue of the solvent, and 
 then in water, is obtained perfectly free from rubber. 
 
 To turn to another topic, at one time the old card-clotliing 
 used in cotton mills formed a valuable raw material for 
 reclaiming purposes, though the term reclaiming is hardly 
 applicable, the rubber never having been vulcanized. This 
 source of supply has, however, decreased of late years as 
 
EE CLAIMED RUBBER. 
 
 125 
 
 not only are the bulk of the rubber-faced cards being 
 vulcanized, but in many cases they have been altogether 
 superseded by the composition cards, which have glue as 
 their basis. One or two other sources of unvulcanized 
 waste rubber are available to the astute collector, but the 
 bulk of such stock is very insignificant compared with the 
 supplies of waste vulcanized rubber. It is upon the latter, 
 and more especially upon goloshes and tyres, that the large 
 factories must depend for their supplies, requiring as they 
 do, not only large quantities of material, but needing it also 
 as far as possible of uniform composition. All the same, 
 compared with what obtained only a few years ago, the 
 organised collection of rubber goods of various classes has 
 grown apace. The erstwhile query as to what becomes of 
 all the pins sold, has not, it is understood, been satisfactorily 
 answered. Any such query with regard to rubber goods 
 has been answered to a great extent in the preceding pages, 
 and if the progress already made continues, there will be 
 few rubber goods indeed which do not find their way back 
 again to the factory after performing useful service outside. 
 
 With regard to the extended use of reclaimed rubber at 
 the present day, it has already been attributed largely to 
 the high price of the new rubber. But other considerations 
 have to be taken into account, more especially the improve¬ 
 ment in the quality, owing to scientific supervision of the 
 processes of manufacture. Chemical and physical testing- 
 forms now an important part of the routine of the reclaiming- 
 works, and in ordering certain brands the rubber manufac¬ 
 turer can depend on getting a product which varies in 
 different deliveries no more, or perhaps even less, than does 
 raw rubber of the second or third grade. Further, the 
 
126 
 
 INDIA-RUBBER. 
 
 experience of late years has shown that reclaimed rubber 
 can he used with advantage in place of oil substitute, and it 
 would probably be found, if statistics were available, that, 
 allowing for the growth of the rubber industry, the use of 
 substitute in such directions as it was formerly employed 
 has decreased considerably. 
 
 It may be contended that this subject has received more 
 attention than it warranted; but as an integral and 
 important branch of the rubber industry it seemed to 
 deserve more notice than other writers have given to it, 
 especially because as a field for the inventor it is clear that 
 its possibilities are not by any means exhausted. 
 
CHAPTER VIII. 
 
 THE WASHING OF CRUDE RUBBER. 
 
 Having now treated of the natural history and production 
 of the crude rubber, we come to the point at which it enters 
 the factory to be made into the various articles of commerce. 
 The first process it goes through is a thorough washing, in 
 order to remove the impurities referred to in previous 
 chapters. Naturally, some brands require much more 
 cleansing than others, but the machinery employed for the 
 purpose is the same throughout, with the exception of the 
 partial use of the hollander for African brands. 
 
 The first process consists in boiling the rubber in water 
 in cast-iron tanks or wooden tubs in order to soften it. 
 After some hours the large pieces are then sliced up with 
 knives, or more often by means of powerful shears, one 
 blade of which is fixed to a wooden stand, the other being 
 operated by the workman. Of late years a few firms have 
 replaced this treatment in the case of dirty African rubbers 
 by the use of a machine called a hollander, in which the 
 slicing up is done by a series of knives working in a tank 
 of hot water. By this means the sand is removed to a 
 greater extent than in the ordinary way of boiling the sliced 
 rubber in hot water. Generally speaking, this constitutes 
 the usual and only process in order to remove as much 
 extraneous matter as possible before the rubber goes through 
 
128 
 
 INDIA-RUBBER. 
 
 the washing process proper. The washing mill of to-day is 
 the same in principle as that of fifty years ago, only it is as 
 a rule of greater capacity and heavier build. Essentially it 
 consists of two cast-iron rollers resting horizontally side by 
 side, a common size in present practice being 2 ft. lOin. 
 by 14 in. 
 
 The roller may have the surface plain, or it may be 
 grooved with straight, rifle or spiral cuts. Different rubber 
 manufacturers have their own ideas on this point, and rollers 
 cut in a variety of ways are to be met with. The rollers 
 revolve inwardly at different speeds, their distance apart 
 being regulated by screws on the front part of the roller 
 frame. The general arrangement of the machine will be 
 easily understood from the illustration (Fig. 10), and it 
 will be unnecessary to go into details, which are purely 
 mechanical. It may, however, be mentioned that the power 
 required for this work is such that direct driving by means 
 of cog-wheels from the main shaft is now the general rule, 
 and the belt-driven machine that is figured in older books 
 may be considered obsolete. 
 
 In the actual washing process the workman places by 
 hand small quantities of the rubber between the rollers on 
 which a stream of cold water is constantly running. The 
 gripping action of the rollers tears the rubber into pieces, 
 the while the stream of water removes the impurities. 
 After passing several times through the rollers the cleansed 
 rubber takes the form of a corrugated sheet containing as 
 impurities hardly a trace of anything except the resins 
 already referred to. These being insoluble in water and of 
 an adhesive nature cannot be removed in this way. 
 
 The capacity of the washing machines in general use is 
 
TIIE WASHING OF CRUDE RUBBER, 
 
 129 
 
 such that one man can wash 600 lbs. of rubber in a day of 
 ten and a half hours. The work is not free from risk, and 
 the accidents which have occasionally occurred in the past 
 have led to the use of certain appliances calculated to protect 
 the workman from the results of any inattention. In Great 
 Britain such safety appliances are not compulsory, but in 
 
 FIG. 10. —WASHING ROLLS. 
 
 certain Continental countries, notably Germany, Austria 
 and Belgium, the washing machines and mixing rolls 
 are bound by law to be provided with them. Of late 
 years it has become customary in English works where 
 no special contrivances are used to provide the workman 
 with a wooden pole to push the rubber between the rollers 
 instead of using his hands. The more general tendency, 
 however, is to adopt the instantaneous disengaging gears, 
 
 I.R. K 
 
130 
 
 INDIA-RUBBER. 
 
 which are now fitted by some, if not all, of the rubber 
 machinery makers at the request of the manufacturer. 
 The details of these contrivances cannot be entered into 
 here, and mention can only be made of that which was 
 designed by Franz Clouth, and which is in regular use in 
 his works at Cologne Nippes. Most of these contrivances 
 take the form of a friction clutch, which cannot be con¬ 
 sidered the height of perfection for fast-running machinery, 
 and an improvement on this form is seen in Iddon’s special 
 instantaneous disengaging gear, which consists of a cam 
 dog clutch. One of the advantages of the electric driving 
 already mentioned as in use at the Leyland and Birming¬ 
 ham Company’s works is the facility of stoppage in case of 
 accident. In this works the washing and mixing machines 
 have a patent arrangement like a fire-call in close proximity, 
 and on the glass being broken the machinery is instantly 
 stopped. 
 
 Hood, of America, in a patent taken out in 1904, advocates 
 the total immersion of the rollers in water instead of merely 
 allowing a stream to flow over them, and if this can be 
 carried out easily it should lessen the time of washing. It 
 may be taken that the washing process, necessary though it 
 is, certainly destroys the nerve or strength of the rubber to 
 some extent, and this in proportion to the time taken in the 
 operation. Any shortening of this time, therefore, should 
 be advantageous, though it is not possible to say anything 
 with absolute certainty on the point. Granting the truth, 
 however, of what has just been said, it follows that the freer 
 from impurities the rubber is, the less it is likely to lose 
 strength in the washing, and this may be adduced as an 
 additional reason why the collection of the raw rubber should 
 
THE WASHING OE CRUDE RUBBER, 
 
 131 
 
 be carried out as carefully as possible, though it is con¬ 
 ceivable that such considerations do not enter very deeply 
 into the mind of the African native. 
 
 In the washing department of a large factory it is 
 customary to have the rollers of three different makes, the 
 first, or breakers, being of a stronger build than the others, 
 and having deep spiral cuts on the faces so as to get a good 
 grip of the pieces of rubber. The rough sheet from these 
 rollers passes to others less deeply cut on the surface. The 
 third description of roller to which the sheet now passes has 
 the faces smooth, and can be tightened up so as to produce 
 a very thin sheet in cases where rapidity in drying is 
 aimed at. 
 
 Although the two-roll washer is in very general use, three- 
 roll machines were brought out in America some years ago, 
 and are stated to have proved decidedly economical. 
 
 Drying of Washed Rubber. 
 
 The rubber as it comes from the washing machines has 
 to be entirely freed from water, and this is done by hanging 
 the sheets over wooden bars in large darkened rooms, heated 
 by steam pipes to a temperature not above 110° F. Higher 
 temperatures up to 140° F. are given by some authors, and 
 no doubt a considerable variation would be found if the 
 different manufacturers were to give their working details 
 to the world. In Great Britain steam heating is always 
 employed, though at some Continental works, notably those 
 of the Harbnrg-Vienna Company at Wimpassing, Austria, 
 the drying is effected by exposure to the air, direct sunlight 
 being excluded. The time taken in the drying-rooms varies 
 from two to six days, or even more, depending principally 
 
 k 2 
 
132 
 
 INDIA-RUBBER. 
 
 upon the thickness to which the sheets of rubber have been 
 rolled on the washing rollers. Although the great bulk of 
 the water is mechanically held on the surface of the rubber, 
 a certain amount is absorbed in its pores, and this is apt to 
 be tenaciously held. For speed of production, therefore, 
 the rolling into thin sheets appears to be the preferable 
 method, except that, for a given weight of rubber, the drying- 
 rooms must he of considerably greater capacity than for the 
 thicker sheet. In cases where floor space is a consideration, 
 what may be generally acknowledged as desirable may not 
 always be found expedient, and the fact that in many 
 factories we find thick sheets being dried must not be 
 taken as an indication that this in itself represents the best 
 mode of procedure in the minds of those who practise it. 
 The suggestion has been made that after drying for a short 
 time the sheets of rubber should he passed through dry 
 rollers to squeeze out the water of absorption, and there 
 seems little doubt that this procedure would expedite the 
 drying. Although the use of Blackman propeller fans has 
 been adopted to some extent for the purpose of removing the 
 moisture-laden air from the drying-rooms, it is quite a 
 modern practice, and its advantages do not seem to be so 
 obvious as might be supposed. Just at first, when the 
 superficial water is being removed, they certainly act 
 beneficially, but afterwards, when the amount of water 
 given off per hour is comparatively small, they are of very 
 little assistance; moreover, by bringing in external air, which 
 has to be heated, there is an increased fuel consumption. 
 Again, unless means are provided whereby the incoming air 
 may circulate throughout the room, it will not do much good, 
 as it will go straight from the inlet to the propeller. The 
 
THE WASHING OF CRUDE RUBBER. 
 
 133 
 
 arrangement of air passages means the blocking up of 
 the interior, thus making the task of the workman more 
 difficult. Quite possibly others have had a different experi¬ 
 ence in this matter, and in stating his own the author has 
 been actuated more by a desire to call general attention to an 
 interesting subject than to any disposition to speak 
 authoritatively. The topic, although as old as the trade 
 itself, has not had that attention paid to its scientific 
 principles as it would seem to warrant, and the discussion 
 which has recently taken place in the pages of the Gumun 
 Zeitung is to be welcomed as likely to lead to improvement 
 and economy in the future. 
 
 It has been said that the sheets of wet rubber are hung¬ 
 up in the drying-rooms, but this statement must be qualified 
 by the remark that this system is not applicable where the 
 rubber contains a considerable quantity of resin of low 
 melting point. Sheets of this composition, if hung up, 
 would be soon found on the floor, so they have to be laid 
 out on trays or shelves together with certain qualities 
 which do not sheet well, and so have to be dried in pieces. 
 
 Drying in Vacuum Apparatus .—Some fifteen years ago, it 
 was suggested that the wet rubber might be more expedi¬ 
 tiously and cheaply dried in vacuum chambers than by the 
 ordinary process just described, and machinery to this end 
 was introduced by Passburg of Berlin. It was further 
 claimed for this process that it entirely prevented the 
 superficial oxidation of the rubber, which took place during 
 drying at elevated temperatures. The latter point is a 
 scientific and somewhat controversial one, the discussion of 
 which would be outside the scope of the present work. 
 With regard, however, to the subject generally it must 
 
134 
 
 INDIA-RUBBER. 
 
 be said that, while vacuum drying has been adopted in 
 many large rubber factories, its progress, in recent years, 
 has been by no means rapid, and there is a disposition 
 among some of those who praised its advent to secede from 
 their allegiance. This must not be taken to mean that the 
 vacuum plants—and there are now several types emanating 
 from different makers—do not do all that is claimed for them. 
 The question seems to be primarily one of first cost, 
 though it must not be overlooked that the dehydration is 
 performed in a much shorter ’time than in the ordinary 
 process. The differences of opinion which have arisen 
 with regard to the vacuum process are, no doubt, due to 
 the variable composition of the rubbers experimented with, 
 and it may easily be that it presents decided advantages in 
 the case of some brands of rubber, and practically none in 
 the case of others. 
 
 For the subsequent processes of the manufacture it is 
 important that the rubber be quite dry; “ bone-dry ” is the 
 common expression for what is desired and aimed at. It is 
 doubtful, however, if much of the rubber used is actually 
 free from moisture. It is not so very uncommon to find 
 quite a half per cent, of moisture in resinous rubbers, and 
 it depends on the purpose to which the rubber is put 
 whether any damage ensues. Generally speaking, ‘25 per 
 cent, should mark the maximum of water present, and there 
 is no difficulty in getting it down to this figure, which may 
 be considered low enough to preclude any subsequent 
 damage resulting from “blowing.” 
 
CHAPTER IX. 
 
 THE COMPOUNDING OF INDIA-RUBBER. 
 
 Owing to its elastic nature india-rubber lends itself with 
 great facility to admixture with a variety of substances both 
 organic and inorganic, and the preparation of rubber com¬ 
 pounded with mineral matters forms a large part of the 
 factory routine, and, indeed, in many works none but such 
 compounded goods are turned out. Although in a good 
 many cases the main reason for such compounding is the 
 desire to reduce the price of the goods, yet this is by no 
 means the only reason, and the admixture of cheap mineral 
 matter with the rubber cannot, therefore, correctly be 
 described as adulteration. There are many classes of 
 goods where the use of rubber alone would be not only 
 wasteful, but positively disadvantageous, and in such cases 
 the mineral constituents confer decided benefits over and 
 above their effect in reducing the price to the buyer. 
 Having said thus much it must, however, be added in the 
 interests of truth that the capacity of the rubber for taking- 
 up mineral matter has been utilised in many cases to a 
 far greater extent than can he considered expedient either 
 in the interests of the purchaser or for the welfare of the 
 trade. Where the difference in price between the rubber 
 and the mineral is so great, it is not surprising that close 
 
136 
 
 INDIA-RUBBER. 
 
 competition has led to the increasing employment of 
 mineral, an extra 1 or 2 per cent, meaning a reduction 
 in cost which will easily enable one manufacturer to gain 
 business at the expense of rivals who have not gone quite 
 so far in compounding. To such an extent indeed has this 
 practice gone that goods are to be met with in which the 
 rubber is infinitesimal rather than plenary as in past times. 
 It has been suggested that the answer to the query what 
 is rubber may be expressed as follows : “ Rubber is an 
 elastic material used for binding together chalk and other 
 minerals in the manufacture of certain goods.” The reader 
 will see in the chapters on cut sheet and elastic thread 
 that this answer is certainly not universally true, but it 
 cannot be contended that it has no application at all to the 
 trade. One effect of over-compounding has been to excite 
 mistrust as to the suitability of rubber for certain purposes, 
 but when engineers talk about rubber being rubbish, they 
 should see to it that they ask a reputable house for a good 
 quality, and they will perhaps change their opinion. Of 
 course, a good quality will cost more than inferior stuff, 
 and some pains should be taken to discriminate between 
 goods offered at different prices. Considerable injustice has 
 been done in the past to manufacturers of the front rank 
 by reason of their goods having been compared by pur¬ 
 chasers to others of apparently equal quality sold at a 
 considerably lower price, and the same thing is no doubt 
 existent to-day. The accusation levelled at the former as to 
 making exorbitant profits has, in the majority of cases, 
 been entirely unjustified, a fact which would speedily 
 reveal itself to the purchaser if he made careful 
 comparisons of the behaviour of the goods in practice. 
 
THE COMPOUNDING OE INDIA-KUBBEK, 
 
 137 
 
 But not to pursue this somewhat worn, though important 
 topic further, we may proceed to the consideration of 
 the more important chemicals and minerals used in 
 compounding. 
 
 In pursuance of a custom originating in the early days of 
 the industry, it is usual to refer to the various chemicals 
 and minerals as drugs and to their habitat in the factory as 
 the drug-room. This nomenclature seems objectionable, 
 though it has sanction in the common use of chemist and 
 druggist as applied to individuals. On the Continent the 
 chemist is always distinguished from the druggist, and 
 the dealing's of the latter being associated entirely 
 with medicine, it seems inadvisable to introduce the 
 name into manufacturing operations which are not con¬ 
 cerned, except in a very indirect manner, with medical 
 matters. Certainly the term “drug” is shorter than 
 “ chemical and mineral,” but the latter will be used in 
 this volume. 
 
 To merely enumerate the various bodies which have been 
 advocated by inventors as ideal components of rubber 
 goods would encumber more space than would be justifiable. 
 The group of substances would be seen to be of an 
 extremely heterogeneous nature, including powdered coal, 
 oxide of gold, Fuller’s earth, and whalebone. In the 
 majority of cases the substances commonly used are chosen 
 more from their physical attributes of weight, colour, etc., 
 than by reason of their chemical composition, and in only 
 very few cases does any chemical reaction result. The 
 following table gives the chemicals in common use, though 
 no doubt the list might be augmented were the practice of 
 individual manufacturers made public. 
 
138 
 
 INDIA-RUBBER. 
 
 Inorganic Compounding Materials. 
 
 Specific Gravity 
 
 Antimony pentasulphide 
 
 . 4-b 
 
 Asbestos powder . 
 
 . 2-6 
 
 Barytes .... 
 
 . 4-5 
 
 French chalk 
 
 . 27 
 
 Magnesium carbonate . 
 
 . 2-2 
 
 Magnesia .... 
 
 . 8-4 
 
 Lime ..... 
 
 . 3-0 
 
 Lampblack .... 
 
 . *2 
 
 Litharge .... 
 
 . 9-3 
 
 Lithopone .... 
 
 . 3-6 
 
 Plumbago .... 
 
 . 2-0 
 
 Bed oxide of iron . 
 
 . 2-0 
 
 Silica ..... 
 
 . 1-8 
 
 Sulphur .... 
 
 . 2-1 
 
 Vermilion .... 
 
 . 8-1 
 
 Whiting .... 
 
 . 2-8 
 
 White lead .... 
 
 . 6*2 
 
 Zinc oxide .... 
 
 . 5-6 
 
 Zinc sulphide 
 
 . 5*8 
 
 In addition to the above, there are various proprietary 
 articles sold under special names. In these days of 
 chemical analysis such articles are not in so much request 
 as in former times, when the supposed merits of such 
 ordinary bodies as whiting or red oxide of iron, sold under 
 fancy names at enhanced prices, were accepted in blind 
 faith without their claims to notice being subjected to rigid 
 examination. As colouring matters, besides the antimony, 
 lampblack, red oxide and vermilion mentioned above, indigo, 
 ultramarine, green oxide of chromium, cadmium sulphide 
 (yellow), arsenic sulphide (yellow), and various lakes derived 
 
THE COMPOUNDING OF INDIA-RUBBER. 
 
 139 
 
 from coal tar colours have been used. Colouring matters 
 capable of withstanding the processes of vulcanization are 
 not too readily found. Especially is this the case with 
 yellows—chromate of lead loses its colour under the 
 influence of sulphur and heat; cadmium sulphide is 
 expensive, while the poisonous nature of arsenic sulphide 
 is a decided bar to its use. With regard to the toxic 
 properties of the colouring matters used in the trade, the 
 subject only becomes of any real importance in connection 
 with india-rubber toys, a topic which comes up for 
 treatment in another chapter. 
 
 Any enumeration of the properties of the above list of 
 substances would be a matter of pure chemistry, and 
 appears to be uncalled for in this volume. The few 
 observations which it is proposed to make will be con¬ 
 cerned, therefore, with the main reasons for their employ¬ 
 ment as indicated in their specific composition and 
 properties. 
 
 Bed or golden sulphide of antimony has a large appli¬ 
 cation in the manufacture of red rubber goods, nothing 
 having been found to take its place. At one time it was 
 looked upon as a vulcanizing agent able to replace sulphur, 
 but its action in this respect was due very largely, if not 
 entirely, to the free sulphur it contained. This sulphur 
 may amount to as much as 25 per cent., and is rarely 
 below 15 per cent. In some brands a considerable propor¬ 
 tion of hydrated sulphate of lime is also present, resulting 
 from the method of manufacture adopted. In practice it is 
 important to know the amount of free sulphur present in 
 order to regulate the extra amount which it is generally 
 necessary to add to effect a proper vulcanization. 
 
140 
 
 INDIA-RUBBER 
 
 Although usually of an orange-red colour, it is made of 
 varying shades, an almost crimson tint being in demand 
 for certain purposes. 
 
 Asbestos powder and fine fibre find application in certain 
 mechanical goods, such as packings and valves intended for 
 heat resisting purposes. In the powdered form it is practi¬ 
 cally the same thing as French chalk, being very similar in 
 chemical composition. 
 
 Barytes is used in the form of the sulphate (and not as 
 the more expensive carbonate) merely as a weighting 
 material. It is quite unaffected by heat, sulphur, or dilute 
 acids, and is never adulterated itself, though it is largely 
 met with in the cheaper brands of white lead offered to the 
 rubber manufacturer. The price is regulated by the fine¬ 
 ness and colour, special qualities being sold under the 
 names of “ permanent white ” and “ blanc fixe.” 
 
 French chalk, which is a natural silicate of magnesia, and 
 is also known as talc, is used to some extent in compound 
 rubbers, especially in those for electrical purposes, but it 
 is used to a much larger degree in the factory as a means 
 of preventing adhesiveness in unvulcanized rubber. A 
 little of the powder dusted over the surface performs this 
 object admirably, and many goods are vulcanized in trays 
 containing a bed of the material. 
 
 Magnesia is used to some extent in the form of the oxide 
 or calcined magnesia, though, at the present day, to a much 
 greater extent in England as the hydrated carbonate. 
 This is an extremely light ffocculent body, consisting 
 chemically of the carbonate mixed with a certain proportion 
 of the hydrate, and having a decided alkaline reaction. 
 Its composition is somewhat variable, depending upon the 
 
THE COMPOUNDING OF INDIA-RUBBER. 
 
 141 
 
 process of manufacture, and it may be expected that the 
 product of different makers, even if of the same degree of 
 purity, will give varying results in practice. The extreme 
 lightness of the material is due to the retention of air by 
 the particles, the actual specific gravity when it is mixed 
 with the rubber being about 2‘2. It seems advisable to 
 mention this point because some very erroneous views are 
 current with regard to it. The use of magnesium carbonate 
 has increased to a very large extent in late years, although 
 it is decidedly more expensive than many other mineral 
 substances used in the trade. It possesses, however, the 
 properties of lightness and of giving toughness to soft or 
 resinous rubber, to mention only two of its advantages over 
 cheaper bodies, and the general, though somewhat tardy, 
 recognition of its merits has led to a greatly increased 
 demand. Goods in which it has been largely used are 
 solid cab tyres, which, in their perfection, combine compara¬ 
 tive lightness with resiliency and strength. Carbonate of 
 magnesia should be stored in a dry place, as it is apt to 
 absorb hygroscopic moisture in excess of that normally 
 combined. Oxide of magnesium, made by calcination of the 
 carbonate, is used in small quantities as a moisture absorb¬ 
 ing and hardening agent, finding its principal application 
 in the vulcanite manufacture, though of late, especially in 
 Germany, it has been used in tyres and many other goods 
 to facilitate vulcanization. 
 
 Lime, in the form of specially prepared hydrate, is used 
 in small quantities only as an aid in the vulcanization of 
 soft rubbers. Theoretically, the pure oxide, or quicklime, 
 should be more useful than the hydrate, but in practice the 
 latter is nearly always used, as it answers the purpose 
 
142 
 
 INDIA-RUBBER. 
 
 intended, and its employment is unattended with the risks 
 attaching to quicklime. 
 
 Lampblack is a common name for the more or less 
 carbonaceous material serving for the production of black 
 rubber goods. Blacks are sold under various names which 
 may, or may not, have anything to do with their origin. 
 Thus we have lampblack, vegetable black, gas black, etc. 
 This may be unsatisfactory from a scientific standpoint, 
 but, in the trade, blacks are purchased on their intrinsic 
 merits without any particular regard being paid to the name 
 they bear. At the present time light carbon black of good 
 covering capacity is obtainable at a much cheaper rate than 
 ten or fifteen years ago, being prepared by the imperfect 
 combustion of the natural gas exuding from the ground at 
 certain spots in the United States. If this source should 
 give out, a by no means improbable eventuality, we may 
 expect carbon blacks to revert to something like their former 
 price. Adulterated blacks are now rarely, if ever, met with, 
 the density, colouring power, and presence of oily con¬ 
 stituents being the main points which claim the buyer’s 
 attention. Besides being put into the body of the rubber, 
 lampblack is used in making varnish for rubber boots and 
 shoes, black surface macintosh cloth, and other purposes. 
 In a general way the value of a black is directly in pro¬ 
 portion to its colouring power, though there are cases when 
 the presence of an inert mineral substance in a low quality 
 brand comes in useful as a filler. An objection, however, 
 to the use of these common blacks is that the manufacturer 
 does not know exactly what he is using, a point on which 
 it is desirable that he should always possess complete 
 knowledge. 
 
THE COMPOUNDING OF INDIA-RUBBER. 
 
 143 
 
 Litharge occupies the double role of weighting material 
 and sulphur carrier in the vulcanization process, and in the 
 case of dark coloured goods its use is very general. Of late 
 years it has almost entirely replaced the red lead and white 
 lead of earlier times; the use' of these bodies, more par¬ 
 ticularly of red lead, never having been satisfactorily justified 
 on scientific grounds, to the best of the author’s knowledge. 
 In place of the ordinary white lead prepared by the old 
 Dutch process, the sublimed lead, which is mostly a sulphate, 
 but containing a little oxide, has been largely used of late 
 years in rubber factories. Although this was made for 
 some years by the White Lead Company, Ltd., of Possil- 
 park, Glasgow, by Hannay’s patent, the manufacture was 
 subsequently abandoned. A similar product, however, 
 is now being made in New Jersey, U.S.A., by the 
 “ Pitcher ” process. In these processes the white lead, instead 
 of being made from the metal, is produced directly from 
 galena, the sulphide ore, by roasting it in a current of air 
 at a high temperature, the sulphide being oxidised and 
 sublimed as sulphate. This form of white lead, being 
 practically non-poisonous, has advantages over the ordinary 
 carbonate of lead in many of its applications. All these 
 lead compounds combine with sulphur at the vulcanizing 
 temperature to form black sulphide of lead, a fact which 
 goes a long way to explain the non-blooming of goods in 
 which they are used. As copper is found occasionally as 
 an impurity in litharge it should be tested for, otherwise 
 adulteration need not be apprehended. Besides being 
 directly obtained from the oxidation of lead, litharge in fine 
 powder is got as a bye-product in the sodium nitrite 
 manufacture, and in Parkes’ desilverization process. 
 
144 
 
 INDIA-RUBBER. 
 
 Litliopone is a name given to a chemically prepared 
 mixture of zinc sulphide and barium sulphate, it being 
 sold at different prices, according to the proportion of zinc 
 sulphide present. Orr’s zinc white, and Griffith’s zinc white 
 are products of the same character. They are of com¬ 
 paratively modern introduction, and their use in place of 
 zinc oxide in the rubber trade, though pretty general, is by 
 no means universal. Their substitution for zinc oxide 
 certainly constitutes an economy, but a difference of opinion 
 exists among manufacturers as to how far such substitution 
 is generally advisable. 
 
 Red oxide of iron is largely used as a weighting and 
 colouring ingredient for the cheaper classes of goods, where 
 the use of antimony sulphide is precluded from considerations 
 of cost. The chief thing about this chemical which worries 
 the rubber manufacturer is the large number of almost 
 indistinguishable tints in which it is sold. If he asks for a 
 sample the dealer sends him two dozen small packets of 
 varying shades and prices ranging from 6s. to 40s. per cwt., 
 and the odds are that unless a careful examination into the 
 whole matter is made, the wrong substance will be bought. 
 It depends entirely on the particular goods to be made 
 whether a cheap or an expensive oxide should be bought. 
 The main point to remember, however, is that the price 
 corresponds, or should correspond, to the depth of colouring 
 power obtainable, this being determined quantitatively, as 
 in the case of lampblacks, by mixing a certain quantity with 
 white lead and a few drops of linseed oil on a porcelain 
 tablet, and comparing the tints obtained. Venetian red, 
 Persian red, etc., are names under which red oxides of a 
 greater or less degree of purity are sold. While the best 
 
THE COMPOUNDING OF INDIA-RUBBER 
 
 145 
 
 product results from the calcination of sulphate of iron, 
 the commoner ones are merely the ochres dug out of the 
 ground, and, in some cases, used as iron ores. 
 
 Plumbago, or graphite, finds its principal application in 
 the preparation of heat and oil-resisting rubber, and does 
 not call for any particular mention. 
 
 Silica has been largely recommended as a filling material 
 for rubber, but its use has never been extensive. It is in 
 the extremely light form of diatomaceous earth, or kiesulguhr, 
 that it has been repeatedly put before the rubber manu¬ 
 facturer’s notice, but the advantages said to accrue from its 
 use are by no means generally testified to in the trade. 
 This may, of course, be due to a lamentable want of dis¬ 
 crimination on the part of the manufacturers; sellers of 
 rubber chemicals frequently having to complain of the 
 Laodicean attitude adopted by manufacturers towards 
 new and important products brought to their notice. This 
 body consists of the skeletons of minute infusoria, and is 
 found at the bottom of inland lakes in Nova Scotia, 
 Germany and Sweden, a deposit also occurring near Belfast, 
 in Ireland. According to Pearson, it is used in small 
 quantities in America, in various rubber compounds in 
 which it increases both strength and resiliency, though if 
 used in excess it makes a very hard compound; a special 
 instance given of its use being the Jenkins elastic valve 
 packing. In the form of fine sea sand silica is used in ink¬ 
 erasing rubbers. 
 
 Sulphur is used as a vulcanizing agent in the three forms 
 of brimstone, flowers of sulphur, and precipitated sulphur. 
 The use of roll brimstone is limited to the sulphur bath, 
 though in the finely powdered form it sometimes takes the 
 
 i.a. 
 
 L 
 
146 
 
 INDIA-RUBBER, 
 
 place of flowers of sulphur in the ordinary vulcanization 
 process. Probably 90 per cent, of the sulphur used is in 
 the form of flowers of sulphur, of which there are several 
 brands on the market specially prepared for the rubber 
 trade. It would be somewhat invidious to go into details 
 concerning the merits of the respective brands, and it will 
 suffice to say that the essential points of a good sulphur are 
 fineness of subdivision, i.e., freedom from grit and crystals; 
 and neutrality, i.e., absence of sulphur acids; and where 
 manufacturers have a comparatively cheap sulphur offered 
 to them they should satisfy themselves that crystals and 
 acid are absent. Different brands of flowers of sulphur, 
 although they may all test 99 per cent, purity, may vary 
 considerably in their physical characteristics. Although 
 the specific gravity of sulphur is 2, different lots show 
 considerable variation in the space they occupy weight for 
 weight; thus when lightly packed in casks of a particular size 
 one brand may weigh a hundredweight and another not more 
 than three-quarters of a hundredweight. In some factories 
 considerable importance is attached to this point, though there 
 really seems to be nothing in it, the distinction vanishing once 
 the sulphur is thoroughly mixed with the rubber. Again 
 considerable difference in colour is noticeable in brands of 
 equal purity, and any variation in the tint of deliveries is 
 regarded with suspicion at the factory. In this particular, 
 apprehension is not entirely groundless, because the colour 
 is to some extent a guide to the source of origin, though not 
 necessarily an indication of purity. In a general way a 
 bright lemon colour shows the finer qualities of sublimed 
 flowers of sulphur, while the paler tints indicate a lower 
 quality, or it may be powdered brimstone. As regards 
 
the COMPOUNDING OF INDIA-EUBBEE. 147 
 
 acidity, however, the deeper the yellow colour the higher 
 the acid, may be taken as axiomatic. Up to quite recently 
 Sicily has practically supplied the world’s needs of sulphur; 
 now, however, in addition to the recovered sulphur of the 
 alkali trade, and the output from Japan, the utilisation of 
 the deep sulphur deposits in Louisiana has struck a decisive 
 blow at Italian supremacy, though it is to be expected that 
 a working arrangement as to prices will be come to. 
 
 The third kind of sulphur to be mentioned has never had 
 more than a limited application, and this to some extent 
 because of its higher price, and also because its application 
 has not been generally studied or understood. Known 
 variously as precipitated, block, or metallic sulphur it 
 occurs as a white, finely-divided powder, obtained by the 
 decomposition of an alkaline sulphide or sulphydrate by 
 acid. Most of what was formerly used contained about 
 25 per cent, of sulphate of lime, precipitated in conjunction 
 with the sulphur. This constituent must be considered as 
 undesirable; but as supplied in recent years by one firm, 
 at any rate, it has tested 99 per cent, sulphur. Owing to 
 its extremely finely-divided condition it can enter into 
 intimate combination with the rubber, allowing of a less 
 proportion being used than in the case of ordinary flowers 
 of sulphur. With regard to its supposed non-blooming 
 properties further confirmation is needed. 
 
 Whiting, which is ordinary chalk purified by levigation, has 
 considerable application as a cheap filler in rubber goods. 
 
 Zinc oxide is perhaps the most important weighting- 
 material added to rubber goods. Besides giving a white 
 colour, it confers upon the rubber properties with regard to 
 many of its applications which are not possessed by pure 
 
 l 2 
 
1-J8 
 
 INDIA-EUBBEE. 
 
 rubber. Thus its addition to rubber goods must in no wise 
 be looked upon as an adulteration or merely as a cheapening 
 device, a statement which finds support, if such is needed, in 
 the terms of the Admiralty specifications enjoining the use 
 of certain quantities of the material. The presence of even 
 traces of lead compounds spoils the colour of the rubber goods, 
 so the zinc oxide generally used is that which is prepared 
 by burning the metal in a current of air. The products of 
 various chemical precipitation processes never seem to have 
 met with favourable consideration in the rubber factories. 
 In America, however, large quantities of zinc oxide are pre¬ 
 pared direct from a complex carbonate of zinc ore, and the 
 product appears to give entire satisfaction in the American 
 rubber trade, where conservatism is not so rampant as on 
 this side. The American manufacturer is said to examine 
 a substance because it is something new, while the Britisher 
 leaves it severely alone for the same reason. This savours 
 somewhat of exaggeration, no doubt, but at the same time 
 it is not without an element of truth. At the time of 
 writing zinc, like all other metals, is at a high price ; but as 
 regards the future, now that the problem of satisfactorily 
 treating the immense quantities of low-grade complex ores 
 which occur in Australia and other countries has been 
 solved, it must of necessity result that the price will fall 
 considerably before long—that is, in the absence of any 
 gigantic trust. But, not to diverge into purely metallurgical 
 matters, a word may be said as to calamine. This body is 
 frequently referred to in formulae for rubber mixings, but it 
 has a certain amount of mystery connected with it which 
 the author lias never completely penetrated. Calamine is 
 the mineralogical name for carbonate of zinc, but as met 
 
THE COMPOUNDING OF INDIA-RUBBER. 
 
 149 
 
 with in the purlieus of the rubber factory, it used to consist 
 largely of whiting. Pearson’s statement that the use of a 
 little calamine hardens the rubber is interesting. Of late 
 years pure calamine, as precipitated from a soluble zinc salt 
 by sodium carbonate, has had an extended trial as a 
 substitute for zinc oxide, but it is understood that it has 
 not proved satisfactory as a substitute for the oxide. 
 Sulphide of zinc finds regular application where its covering 
 capacity and the smooth surfaces it produces in the case of 
 single textures are considered as compensating for its price. 
 It is also employed in the dental rubber branch. 
 
 \ 
 
CHAPTER X. 
 
 INDIA-RUBBER SOLVENTS AND THEIR RECOVERY. 
 
 Although india-rubber is soluble in many liquids, as far 
 as manufacturing operations on the large scale are con¬ 
 cerned there are only three solvents which call for mention. 
 These are coal-tar naphtha, petroleum spirit or benzine, and 
 shale naphtha. The first is used to the largest extent, as it 
 is undoubtedly the best solvent. Its composition is by no 
 means uniform, being made up of benzene, toluene, and 
 xylene in proportions determined, as a rule, by the market 
 prices of the various coal-tar products. The original solvent 
 naphtha consisted chiefly of xylene with but small amounts 
 of the lower boiling homologues, toluene and benzene. At 
 the present day it may, or may not, consist of xylene, but 
 except that increased volatility results from an admixture 
 of lower boiling homologues, there is nothing to be said 
 against them, the solvent power in each case being for 
 practical purposes identical. Indeed, when 90 per cent, 
 benzol is cheap and solvent naphtha is dear it would pay 
 the manufacturer in many cases to buy the former instead 
 of the latter. During the last few years, owing to a 
 decreased demand, solvent naphtha has been remarkably 
 cheap; while in the winter months the increased use of 
 benzol in the manufacture of carburetted coal-gas has 
 caused appreciation in its price. Such fluctuations in the 
 
INDIA-RUBBER SOLVENTS AND TIIEIR RECOVERY. 151 
 
 relative values of these coal-tar products will continually 
 arise, though in the absence of any great revival in the 
 proofing trade there seems little probability of solvent 
 naphtha rising again to prices which ruled some ten or 
 fifteen years ago. It is bound to form one of the inter¬ 
 mediate products in the distillation of tar for carbolic acid, 
 anthracene, and pitch, whilst, unlike benzol, which is in 
 large request in the coal-tar colour industry, solvent 
 naphtha has a very limited market outside the rubber 
 manufacture. The ordinary contract form for solvent 
 naphtha specifies that 90 per cent, must distil over at 
 160° C. ; in some cases 95 per cent, at 165° C. is stipulated 
 for. The specific gravity varies from '865 to '880, 
 though, as this affords no clue to its real constitution, its 
 determination, at one time looked upon as an important 
 matter in the rubber factory, may as well be ignored. 
 Freedom from heavy oil is an important matter, though 
 this impurity is but rarely met with nowadays. Small 
 quantities of naphthalene, carbon bi-sulphide, and pyridine 
 are common constituents, though rarely in amounts suffi¬ 
 cient to warrant any notice being taken of them. Their 
 objectionableness lies not in any injurious action on the 
 rubber, but in the effect they have on the workpeople 
 exposed to the naphtha fumes. In a general way it may 
 be said that a solvent distilling within a range of 40° C., 
 say from 110° C. to 150° C., is best suited for the manufac¬ 
 ture of proofed cloth, though for quick-drying solutions 
 benzol, which distils within a range of 20° C. and boils at 
 81° C., is preferable. 
 
 Petroleum spirit as a solvent for india-rubber has been 
 used much more extensively on the Continent than in 
 
152 
 
 INDIA-RUBBER. 
 
 England, mainly from considerations of price. As a solvent 
 it is decidedly inferior to solvent naphtha, and, indeed, it 
 would have very little application at all unless it were 
 admixed with a certain proportion of the latter. At the 
 present time, as the price of benzol has fallen on the Con¬ 
 tinent, owing to its increased production as a bye-product in 
 recovery coke ovens, the use of petroleum spirit or benzine 
 in the rubber trade has decreased. Of somewhat variable 
 character, the petroleum spirit shows an even wider range 
 of boiling points than solvent naphtha, though samples 
 ranging from 30° C. to 160° C. are not to be recommended. 
 If only for considerations of fire risk, it is inadvisable to 
 employ a product which commences to distil below 55° C. 
 Such spirit, it may be said, is an after product of the light 
 petrol now so largely used by motorists, and the associated 
 dangers of which are matters of general knowledge. While 
 solvent naphtha consists of the aromatic series of hydro¬ 
 carbons and petroleum spirit of the paraffin series, the third 
 solvent we have to consider consists of the olefine series. 
 Known commonly as shale naphtha, or spirit, it is a product 
 of the shale distillation industry, which is so largely carried 
 on in Linlithgowshire and Midlothian. Although a fairly 
 good solvent for rubber, certainly superior to petroleum 
 spirit in this respect, its characteristic penetrating smell 
 has always been against its more general adoption, even 
 when the price offered decided allurements. Although not 
 unknown in English rubber factories, it is in Scotland 
 where it has been mostly used. With regard to its com¬ 
 position, it should be said that it is now produced of much 
 superior quality to what was usually the case twenty years 
 ago. Not only is there a complete absence of the high- 
 
INDIA-RUBBER SOLVENTS AND THEIR RECOVERY. 153 
 
 boiling, oily constituents which used to be such a menace 
 to its use in waterproofing, but its deodorization has been 
 effected with a considerable degree of success. Its initial 
 boiling point has also been raised in the qualities expressly 
 intended for rubber works, 80° C. to 150° C. constituting 
 now the ordinary range of distillation. 
 
 The following table gives the distillation figures yielded 
 by solvents tested by the author :— 
 
 Description op Solvent. 
 
 
 Solvent 
 
 Naphtha. 
 
 Solvent 
 
 Naphtha. 
 
 Shale 
 
 Spirit. 
 
 Petroleum 
 
 Spirit. 
 
 Specific gravity at loA^C . 
 
 870 
 
 875 
 
 830 
 
 720 
 
 Boiling point 
 
 110°C. 
 
 116°C. 
 
 70°C. 
 
 3S°C. 
 
 10 per cent. 
 
 121 
 
 129 
 
 91 
 
 65 
 
 20 ,, ... 
 
 124 
 
 133 
 
 98 
 
 71 
 
 30 ,, ... 
 
 125 
 
 137 
 
 104 
 
 76 
 
 40 „ . . . 
 
 128 
 
 141 
 
 111 
 
 81 
 
 50 ,, ... 
 
 132 
 
 144 
 
 118 
 
 85 
 
 60 ,, ... 
 
 135 
 
 146 
 
 126 
 
 91 
 
 70 ... 
 
 138 
 
 148 
 
 132 
 
 97 
 
 80 ,, ... 
 
 141 
 
 151 
 
 140 
 
 105 
 
 90 ,, ... 
 
 147 
 
 156 
 
 153 
 
 121 
 
 95 ,, ... 
 
 155 
 
 161 
 
 158 
 
 143 
 
 The Recovery of Naphtha .—The great bulk of the solvent 
 naphtha used in rubber factories, and all of that employed 
 in card cloth works, is used in connection with “ spreading,” 
 and after it has served its purpose it is dissipated by heat. 
 Not unnaturally, the idea of recovering it for use over again 
 has attracted a good deal of attention, and at one time or 
 another various arrangements have been devised whereby 
 this could be effected. It would occupy too much space to 
 follow the history of this interesting subject from its birth 
 to its present stage of development, though a synopsis of its 
 
154 
 
 INDIA-RUBBER. 
 
 main features may be given. Speaking generally, as regards 
 the waterproofing trade, at the height of its prosperity, only 
 one or two recovery plants have been in regular operation. 
 In many cases money has been lost by the erection of plant 
 by engineers who had no close knowledge of the properties 
 of the solvent they were dealing with, and in other cases 
 plant which under favourable conditions would have worked 
 as well on the large scale as in the laboratory model proved 
 ineffective under the factory conditions involved. It is one 
 thing to condense hydrocarbon vapours as obtained pure 
 from the heated liquid, and quite another to condense them 
 on the large scale when admixed with air. Whatever means 
 of condensation have been suggested, the collection of the 
 vapours from the spreading machines has been the same in 
 principle in all cases—namely, the employment of a close- 
 fitting hood, usually of galvanized sheet iron. It is 
 imperative, however, that a certain amount of air gets 
 mixed with the naphtha vapours, thus complicating the 
 ensuing condensation. The amount of admixed air will, of 
 course, depend upon the number of times the workman 
 opens the door of the collecting hood in order to examine 
 the work in progress, and also, to a great extent, upon the 
 regularity of the work. Intermittent working, which is by 
 no means uncommon in the proofing branch, is all against 
 economical results being obtained in the recovery process, 
 as is also the separation of the spreading machines in a 
 number of small rooms, instead of having them all con¬ 
 centrated in one compartment. Various other causes might 
 be cited which have conduced to the unsatisfactory working 
 of recovery plant in rubber factories in the past. With 
 regard to more recent years, the decline of business and the 
 
INDIA-RUBBER SOLVENTS AND THEIR RECOVERY. 155 
 
 reduction in the price of the solvent have operated against 
 the erection of new recovery plant. If we turn, however, to 
 the card cloth industry, of which more is said in another 
 chapter, we find the recovery of naphtha the rule rather 
 than the exception. The general conditions of work are 
 here more favourable than in the case of the waterproof 
 clothing manufacture. The rubber to be spread is always 
 of the same composition, with the same weight of naphtha, 
 and there is no such necessity for the workmen to open the 
 lid of the hood to look for or adjust any incidental defects 
 as the work progresses. Becovery plants have been in 
 regular operation in Lancashire and Yorkshire for many 
 years with an average recovery of 75 per cent, of the 
 naphtha used. In these recovery plants, as made by 
 Siddeley and Co., of Liverpool, the naphtha vapours are 
 drawn from the hoods and condensed in metal tubes cooled 
 down below zero by an ammonia refrigerating machine. 
 The condensed naphtha in the older plants is rarely quite 
 pure enough to be used again as it is, and is usually returned 
 to the distillers for redistillation in order to free it from oil 
 derived from the condensing machinery. In the more 
 recent plants erected by the same firm oil lubrication is 
 done away with, and there is no need to redistil the 
 naphtha. Thus, whatever the rubber manufacturer may 
 have to say on the subject as the result of his own expe¬ 
 rience or non-experience, it is a fact that the recovery of 
 naphtha from spreading machines is not only perfectly 
 feasible, but is also, under favourable circumstances, attended 
 with marked economical results. In saying this it should 
 not perhaps be overlooked that when the majority of these 
 recovery plants were put down the comparatively high price 
 
156 
 
 INDIA-RUBBER. 
 
 of the solvent held out an inducement for the expenditure 
 of capital which might not have been considered justifiable 
 when prices fell. However, even with naphtha at 6d. per 
 gallon, the recovery plants were all, to the best of the 
 author’s knowledge, kept in operation, a fact which testifies 
 abundantly to their economy. With regard to this point of 
 economy, it should be pointed out that the advantages 
 accruing to recovery are not all comprised in the cash value 
 of the naphtha recovered. The purification of the air of the 
 spreading-room is of no small moment, as it makes the 
 work much more agreeable to the operatives, and also 
 reduces the danger of fire to a minimum. 
 
CHAPTER XI. 
 
 INDIA-RUBBER SOLUTION. 
 
 This product, which has become of such great familiarity 
 since the rise of the bicycle, is made both at the rubber 
 works and also to a large extent by cycle agents and other 
 retailers, who buy the masticated rubber from the factory. 
 This wider dissemination of the trade had its origin no 
 doubt to some extent in the desire to save intermediate 
 profits, but it is also largely attributable to the somewhat 
 onerous restrictions placed upon the transit of the solution 
 by railway and steamship companies. Very little solvent, 
 as ordinarily employed, has a flash point over 78° F., and 
 thus the solution made from it has to be dispatched under 
 specified conditions and at special rates. One can hardly 
 blame the carrying companies for safe - guarding their 
 interests, though too much has been made of the so-called 
 explosive nature of the solution. Even if a light should be 
 applied to a vessel of it, it will merely flare up and soon 
 burn out, and explosive effects can only be experienced when 
 the vapours from uncovered vessels evaporate into the air of 
 a closed room. In such cases the explosive mixture will 
 detonate with probably disastrous results to the immediate 
 vicinity if a light is brought into contact with it. Seeing 
 that these facts, simple though they are, appear to be as yet 
 imperfectly understood by many of those who store and 
 deal in rubber solution, it can hardly be contended that the 
 regulations attending its storage enforced by the London 
 
158 
 
 INDIA-RUBBER. 
 
 County Council and municipal bodies' throughout the 
 country are too stringent. With regard to the flash point 
 of the solvents, it has been largely supposed that ordinary 
 solvent naphtha does not come within the 78° F. limit, 
 but between this and the 120° F. limit. Careful determi¬ 
 nations, however, which the author has made with a Board 
 of Trade standard apparatus, show that ordinary solvent 
 naphtha with an initial boiling point below 100° C. very 
 frequently flashes about 71° F. With regard to solution 
 made with petroleum and shale spirits, it may be taken that it 
 will always come within the 78° F. limit. In cases where it 
 is important that the solution shall be well above the 73° F. 
 limit, it is necessary to use the regular solvent naphtha, 
 consisting of xylenes and a little toluene, but practically 
 free from benzene or the light products of Scotch cannel coal; 
 such naphtha, which does not boil below 125° C. has a flash 
 point about 85° F. In making the solution it is not suffi¬ 
 cient to merely add the rubber to the naphtha. In order to 
 get a uniform product the two must be churned together for 
 some time. This treatment is necessary to break down, so 
 to speak, the insoluble or fibrous constituent already men¬ 
 tioned as being a component part of rubber, otherwise only 
 the soluble portion would be in solution and the fibrous 
 constituent merely swell up. Various machines are in use 
 for solution making, some form of pug-mill with a tightly 
 fitting lid being the most common. With regard to the 
 strength of the solution this varies according to price and 
 specific requirements. The British War Office, which uses 
 a good deal in the Carriage Department at Woolwich, 
 stipulates for 18 per cent, of rubber, and this may be taken 
 as the highest strength which can conveniently be obtained 
 
INDIA-RUBBER SOLUTION. 
 
 159 
 
 and satisfactorily employed. In other cases, where it is 
 used in the cycle and motor repairing business or in the hat 
 trade, it is generally weaker in rubber, 9 to 15 per cent, 
 being limits within which it is commonly sold. Although 
 at one time Para rubber was exclusively, or, at any rate, 
 very generally, used for solution making, at the present 
 time lower grades find considerable employment. The item 
 of cost has doubtless a good deal to do with this, but it 
 must not be considered as the exclusive reason for the 
 change of procedure. For some purposes a stickier and 
 slower drying solution is preferred, and in this case the 
 cheaper resinous African rubbers do as well as fine Para, 
 and with a decided saving of cost—to the manufacturer 
 at all events. But the substitution of lower grades of 
 rubber for the best does not measure the whole change 
 which has taken place from former practice. A weak 
 solution has been strengthened by the addition of foreign 
 bodies, among which may be mentioned common rosin, a 
 practice of which it is difficult to say anything favour¬ 
 able. Another departure which we seem to owe to 
 America is the compounded solution sold for solutioning 
 fabric intended for motor tyre repairing purposes. The 
 budding trade in this seems, however, to have been 
 arrested at an early stage by the buyers getting an 
 expert to tell them the composition of the solution and 
 then promptly making it for themselves. Rubber solution 
 can be made with other solvents than naphtha and 
 petroleum spirit, but there are objections to their use, 
 except on a very small scale, for special purposes. 1 In the 
 
 1 Quite recently carbon tetrachloride has been used on the large 
 scale for making solution. 
 
160 
 
 INDIA-BU13BER. 
 
 case of a certain proprietary article for tyre mending the 
 rubber is dissolved in bi-sulphide of carbon, a liquid which 
 ought to be barred in this connection, in the author’s 
 opinion, by reason of its toxic and inflammable nature. 
 Quite recently a rubber solution, said to be non-inflam¬ 
 mable, has been put on the market, and if its claims in 
 this respect are found to be substantiated it will certainly 
 be welcomed by the retailer who goes in constant fear 
 of contravening the Petroleum Acts, or of having his 
 insurance premium raised. An interesting development 
 of the solution industry is the recent attempt to use 
 vulcanized rubber. The principal drawback appears to lie 
 in the necessary use of heat in order to get the rubber 
 into solution. This effects a partial decomposition of the 
 rubber and causes the solution to dry very slowly, some¬ 
 times indeed taking weeks. Such solution is, however, 
 extremely tenacious, and might prove of distinct value in 
 certain applications. It is noteworthy in this connection 
 that Hancock’s early experiments with regard to the 
 utilisation of vulcanized scrap rubber were directed to the 
 formation of rubber cements. 
 
 A good deal of rubber solution is used in the golosh 
 manufacture, for which purpose it is mixed with sulphur 
 and litharge in order that it may subsequently become 
 vulcanized. In America a large amount of rubber solution 
 is bought as a cementing and waterproofing agent in the 
 leather boot manufacture. Compared with what obtains in 
 England, the American boot seems rather a weird produc¬ 
 tion, what with brown paper, glucose, and rubber solution 
 entering into its composition, though no doubt all-leather 
 boots are to be had for the asking. 
 
CHAPTER XII. 
 
 FINE CUT SHEET AND ARTICLES MADE THEREFROM. 
 
 The manufacture of cut sheet rubber is a special branch 
 of the rubber industry, and is confined to two or three firms 
 only. Besides the employment of considerable capital and 
 expensive machinery, there are technical difficulties involved 
 which necessitate expert knowledge on the part of either 
 master or man. At one time the two large Manchester 
 firms supplied the world’s needs in this article, but at the 
 present time besides the Leyland and Birmingham Rubber 
 Company, which has taken up the branch, it is now made 
 in France, Belgium, Germany, and Italy, and in a small way 
 by two firms in America. Although for many years made 
 only from the best Para rubber, second and third quality 
 sheet is now on the market, the movement in this direction 
 having been initiated by Germany some fifteen years ago. 
 Seligmann in his book puts on record with what surprise 
 Henriques found a quantity of oil substitute when analyzing 
 a sample of German cut sheet. Where such sheet containing 
 oil substitute is honestly sold for second or third quality 
 there does not seem anything to be urged against it, except 
 where it is used for certain classes of domestic and surgical 
 goods. That many of such goods have shown a deteriora¬ 
 tion in quality in recent years is a fact of which there is 
 abundant medical testimony, and it would be to the interests 
 
 I.R. 
 
 M 
 
162 
 
 INDIA-RUBBER. 
 
 of the community that doctors who imagine they are buying 
 pure rubber should be informed of the fact when such is 
 not the case. It is not suggested that any application of 
 the Food and Drugs Act is desirable or possible in the case 
 of rubber goods, but it certainly seems advisable for medical 
 men to know exactly what they are buying, and to bring it 
 home to them that cheap goods are almost of a certainty 
 adulterated. Cut sheet rubber besides being used up in the 
 factories of its origin is largely sold to smaller establish¬ 
 ments, including private workshops, where it is made up 
 into various small articles. This requires practically no 
 machinery, the edges of the rubber being joined together 
 by pressure, and the vulcanization as a rule being by the 
 cold-cure system already referred to. A good deal of English 
 cut sheet goes to Paris, where the feuille Anglaise has long 
 been a well-known product, and is still considered the best 
 obtainable. The Germans refer to it as Patent Gummi, 
 though the reason for this synonym is not obvious. The 
 great bulk of the cut sheet made has the brown colour which 
 the rubber gains under treatment, and indeed in the 
 thinnest sheets it is almost transparent. At the present 
 day there is but little demand for green sheet, but red sheet, 
 which is produced by adding vermilion to the rubber before 
 being made into the block, is manufactured in considerable 
 quantities. With regard to the process it will be readily 
 recognised that it is necessary to get the rubber into a per¬ 
 fectly homogeneous condition, and further that it must be 
 quite rigid if uniform sheets are to be cut from it. These 
 effects are obtained by mastication, hydraulic pressure and 
 freezing. The several processes briefly described are as 
 follows :-—The washed and dried rubber is warmed up or 
 
FINE CUT SHEET AND ARTICLES MADE THEREFROM. 163 
 
 broken down, as it is variously called, on large mixing rolls 
 and is then put into a machine called the masticator, which 
 consists essentially of an outer iron casing and a fluted steel 
 roller revolving within it, the axis being set slightly obliquely. 
 The rubber is squeezed between the roller and the casing, 
 and the heat engendered serves to expel any traces of 
 moisture and also air held in the pores of the rubber. To 
 prevent the heat rising too high the casing has a jacket 
 through which cold water circulates. After some time the 
 rubber, which is now in the form of a sausage, is removed to 
 make way for a fresh quantity. For rectangular blocks 
 these batches of masticated rubber are put into iron presses 
 about 6 feet by 1 foot, tightly screwed up and submitted to 
 hydraulic pressure, after which they are frozen in an ice¬ 
 house, an operation which takes a considerable time. These 
 blocks can, of course, only produce sheets of their own 
 dimensions. Where longer and wider sheets are required, 
 three of the masticated batches of rubber are put into a 
 vertical press and submitted to a pressure of one-and-a-half 
 to two tons on the square inch. A circular block is then 
 formed from which, after it has been frozen, sheets of as 
 much as 600 yards in length can be cut. The cutting 
 machine now employed for circular blocks is a triumph of 
 mechanism, and it has been improved to such an extent that 
 sheets of which 165 go to the inch can now be cut by one 
 firm at least in the trade. 
 
 Generally described, the circular block cutting machine 
 consists of a knife with a long straight blade, something like 
 a mowing machine knife, and making up to 2,000 vibrations 
 per minute. The speed of the knife can be varied by the 
 cones which form part of the driving mechanism. The 
 
 m 2 
 
164 
 
 INDIA-RUBBER. 
 
 sheets are cut in eighteen or twenty different thicknesses 
 or counts. The rectangular blocks are put on a horizontal 
 moving carriage, which can be raised or lowered to bring it 
 up to the knife, and these machines, it may he said, are not 
 of such a complicated nature or exclusive design as those 
 used for circular block cutting. 
 
 Each firm has its own special machinery for compressing 
 the blocks and cutting the sheets, and not unnaturally a 
 good deal of reticence is displayed with regard to the 
 details. In modern times the old system of freezing the 
 blocks of rubber in a mixture of ice and salt has been 
 succeeded by freezing chambers and refrigerating machinery, 
 but even with this advance it may take quite two months to 
 freeze a block solid to the core, which is necessary in order 
 that a continuous sheet may be cut. As a refrigerating 
 chamber may contain rubber up to ;£ 10,000 in value, 
 representing locked-up capital, it will be recognised that 
 this branch of the rubber business cannot be entered upon 
 by firms without considerable capital resources. 
 
 Cut sheet can always be distinguished from what has 
 been spread or rolled from a solution of the rubber in 
 naphtha by the knife marks; at least, this should be the 
 case. We live, however, in a progressive age, and Franz 
 Clouth, in his book, refers to the use in some works or other 
 in the Fatherland of an embossed calender, whereby rolled 
 sheet has the apparent hall-mark of the knife-cut impressed 
 upon it, and to such effect that any but the practised eye 
 would be deceived. The author mentions this on the high 
 authority quoted, not having any personal knowledge of the 
 practice or any information as to whether it is limited to 
 Germany or not. 
 
FINE CUT SHEET AND ARTICLES MADE THEREFROM. 165 
 
 Among the many uses to which cut sheet rubber is put, 
 either in the vulcanized or unvulcanized condition, may be 
 mentioned tobacco pouches, surgical goods of various kinds, 
 what are known as “ feeding-bottle ” outfits, dress pre¬ 
 servers, black india-rubber tubing, balloons, squeakers, 
 and such like products of an advanced civilization. The 
 electrical industry also makes considerable demands upon 
 cut sheet in the form of strip in the cable manufacture, 
 though in its special application of a first coating on the 
 wire its popularity is also shared by spread and rolled strip. 
 
 To say a few words about some of the more important of 
 these articles, commencement may be made with the tobacco 
 pouch, which is largely, though by no means exclusively, 
 made from cut sheet. The process is a comparatively simple 
 one, the two pieces of rubber being cut or stamped out of 
 the sheet to the required shape and the edges joined by 
 pressure of the work-girl’s finger and thumb. Vulcaniza¬ 
 tion is effected by the hot vapours of chloride of sulphur, the 
 pouches, put on to wooden moulds, being hung up in a steam- 
 heated chamber. 
 
 Another process of vulcanization consists in immersing 
 the pouch in a sulphur bath and afterwards heating it in 
 steam. In the case of the well-known red crocodile pouch 
 of Warne and Company, spread sheet containing red 
 sulphide of antimony is used, and the vulcanization is effected 
 by heat. This, of course, does not call for consideration under 
 cut sheet goods, but it is mentioned here as a matter of 
 convenience. Bed steam-cured pouches are also made by 
 the Davidson Rubber Company, U.S.A. On the Con¬ 
 tinent, the pouch manufacture has made but little progress, 
 this being no doubt largely attributable to the fact that the 
 
166 
 
 INDIA- RUBBER. 
 
 demand for the article is but slight. In Austria and the 
 Balkans tobacco is almost universally carried in tins, and the 
 author can testify to the difficulty in replacing a mislaid 
 pouch. The methods of vulcanizing pouches just mentioned 
 do not comprise all that have been or are at the present time 
 in vogue, nor is the procedure in any particular factory 
 necessarily limited to any one process. Three or four 
 different methods may be in use in the same factory, 
 according to the nature of the rubber and the form of the 
 pouch. In certain cases where the use of heat is precluded 
 the chloride of sulphur in the vapour cure is volatilized 
 by the admixture with it of a small quantity of fuming 
 nitric acid. This agent itself, or rather the red vapour of 
 nitrogen dioxide which it evolves, has a sort of vulcaniz¬ 
 ing action upon the rubber. As, however, it may easily 
 prove very destructive to the rubber if in excess, its use 
 suggested, it is understood, first by Hancock, cannot be 
 recommended. Where it is employed, as mentioned above, 
 it must be considered merely as ancillary to the vaporiza¬ 
 tion of the chloride of sulphur, and not as a vulcanizing 
 agent in itself. 
 
 In making the small toy balloons the two pieces of sheet 
 rubber are stamped out and joined together by a machine 
 hammer, a very noisy operation, which causes the workgirls 
 to stuff their ears with cotton wool. Where the rubber has 
 to undergo distension it is important that the joints be well 
 made, and this can only be done effectually by hammering. 
 The vulcanization is brought about by dipping in a weak 
 solution of chloride of sulphur in carbon bisulphide, an 
 operation of some delicacy in the case of the very thin 
 balloons. After the chemical fumes have thoroughly 
 
FINE CUT SHEET AND AETICLES MADE THEREFEOM. 167 
 
 evaporated by exposure to air in a tray of French chalk, 
 each balloon is blown out by compressed air, a certain 
 number generally bursting under the test, and having to go, 
 therefore, into the waste rubber receptacle instead of into 
 the packing box. It was more especially with regard to this 
 and other branches of cut-sheet goods manufacture that 
 the regulations as to the use of carbon bisulphide were 
 introduced. Things are now carried on in a manner very 
 different from what was at one time the case, and there is 
 no reason to suppose that any permanent injury to health 
 will accrue to those who are engaged continuously in this 
 industry. At the same time, there is no doubt that the 
 manufacturers and workpeople alike would be only too 
 glad if the carbon bisulphide could be altogether banished 
 in favour of a less inflammable and noxious substitute. 
 Unfortunately, however, after the trial of numerous substi¬ 
 tutes, manufacturers have been forced to go back again to 
 their original procedure, no other liquid yet proposed having- 
 been found to possess the properties of carbon bisulphide 
 in instantaneously softening the surface of the rubber so 
 as to allow the chloride of sulphur to do its work. This in 
 a general way, the author being aware that for certain 
 purposes on a small scale the use of a hydrocarbon solvent 
 in cold curing has been found satisfactory. 
 
 llightly or wrongly, in the case of several classes of goods 
 where the edges are joined together by pressure, this proce¬ 
 dure has been held to constitute a source of weakness, and 
 some manufacturers make a good deal of the fact that their 
 goods are made by a seamless process. In such cases 
 they have to be formed from a solution of rubber which is 
 allowed to dry, in the case of hollow articles, on a mould of 
 
168 
 
 INDIA-EUBBEK. 
 
 the requisite shape. One advantage accruing to this form 
 of procedure is that the rubber can be mixed with sulphur 
 and subjected afterwards to the more satisfactory steam 
 vulcanization. 
 
 Dress preservers were formerly made usually from cut 
 sheet and vulcanized, either in the cold cure liquor or in the 
 hot chamber with chloride of sulphur. Of late years, how¬ 
 ever, they have been made of greater stability by using 
 rolled sheet steam vulcanized. Balata has also supplanted 
 rubber a good deal in this branch. Certain American 
 factories have produced these goods by various processes, 
 one being the compound proofing of stockinette, and have 
 enjoyed greater popularity for their products than have 
 European makers, though to judge by the output of a large 
 French factory this supremacy is being stoutly challenged. 
 Now that tailors are using these hygienic adjuncts so largely, 
 especially for uniforms, the business is likely to prove an 
 increasing one, and the article is more suitably described 
 by its French equivalent of sous-bras, than by the term 
 commonly employed in England and America. The import¬ 
 ance of neutrality in the finished product needs no emphasis, 
 and effectual means to secure this must be employed where 
 chloride of sulphur is the vulcanizing agent. 
 
 Cut sheet rubber, as used in the card-clothing manufacture, 
 deserves a special paragraph, because it is made by a process 
 different from that which has been described above. Card 
 clothing, it may be advisable to explain, is used in the rotary 
 carding machines of cotton and wool spinning mills. For 
 its specific uses books on the textile manufactures should be 
 consulted, but in general form it consists of layers of cotton 
 cloth faced with india-rubber through which short steel wires 
 
FINE CUT SHEET AND ARTICLES MADE THEREFROM. 169 
 
 are placed close together. The manufacture is a somewhat 
 special one, and is practically confined to certain works in 
 Yorkshire and Lancashire wholly devoted to it. The object 
 of the rubber facing to the cards is to give an elastic base 
 to the steel wires, thus imparting to them the desired springi¬ 
 ness. The rubber surface is sometimes of cut sheet and 
 sometimes of spread sheet, the latter being used both pure 
 and vulcanized. A good deal of card clothing is also made 
 nowadays in which the rubber is altogether dispensed with 
 in favour of a certain substitute. At the large works of 
 Horsfall and Bickham, of Manchester, the whole of the 
 rubber used, both cut and spread sheet, is manufactured. 
 Here, as also at the Yorkshire works of the Card Clothing 
 Manufacturers’ Association, the rubber is not masticated, 
 but after having been washed it is cut up into small pieces, 
 dried in stoves at a high temperature, and compressed into 
 a circular block by hydraulic pressure. The sheet subse¬ 
 quently cut from the block is of a lighter colour than 
 the sheet which has been masticated, and it is always 
 distinguishable from the latter by its peculiar mottled 
 appearance. By this mode of manufacture it is claimed 
 that a tougher and more durable sheet is produced than 
 where the rubber has to undergo the mastication process, 
 though the author is not aware of any reliable series of 
 tests which may be accepted as indisputable proof of this 
 assertion. In view, however, of the deterioration which it 
 is generally agreed that rubber suffers in prolonged masti¬ 
 cation, a primd-facie case is certainly made out for the above 
 contention. The use of sheet rubber in card clothing was 
 first proposed by Hancock as far back as 1828, leather being 
 the material commonly used at that period. It might be 
 
170 
 
 INDIA-RUBBER. 
 
 mentioned that besides the three large Lancashire firms 
 who make fine cut sheet for general purposes, small sheets 
 of not more than a foot in length are made by one or two 
 London firms in connection with the manufacture of surgical 
 goods. 
 
 As vulcanization in the sulphur bath has only been men¬ 
 tioned in general terms, it may be of interest to give a more 
 detailed account of the procedure followed for small cut- 
 sheet articles. The made-up goods are put in a warm stove 
 for some hours in order to perfect their joints, and they are 
 then introduced into the sulphur bath upon forms of wood 
 or metal, or in some cases a weight is tied to them to keep 
 them down in the sulphur. They remain for about an hour 
 with the sulphur at 240° F., when absorption takes place 
 into the pores of the rubber. The temperature is then 
 raised to about 270° F. for another hour or so, until the 
 vulcanization is considered to be complete. Instead of going 
 by the temperature and duration of time, it is usual for the 
 man in charge to put a number of small pieces of rubber of 
 the same thickness as the goods into the bath at the com¬ 
 mencement of the operation. By a string which is attached 
 to them these test samples can be drawn out from time 
 to time and examined, and when vulcanization is shown 
 to have been effected the goods are taken out of the bath 
 and put into cold water. Their surface is covered with 
 sulphur crystals, and these are either removed by rubbing 
 with pieces of wood, or better by boiling in a caustic alkali 
 solution, whereby the rubber becomes of a deep black shade. 
 A subsequent polishing process may also be utilised to give 
 a glossy appearance to the rubber. 
 
CHAPTER XIII. 
 
 ELASTIC THREAD. 
 
 It has been already mentioned that the monopoly first 
 enjoyed by Macintosh and Company, and afterwards shared 
 by one or two other English firms, has of late years been 
 challenged by other countries. Although it is safe to say 
 that England is still by far the largest producer, yet the 
 manufacture is to-day carried on in the United States, 
 Germany, Italy and Russia. With regard to France, which 
 is a large user of the material, the manufacture after having 
 been carried on on the small scale for some years has now 
 ceased, though it was in Paris that the greatest interest 
 was at first taken in the subject, though the threads were 
 made by quite a different process than that afterwards 
 adopted on the large scale in England, and universally 
 employed at the present time. In the original factory of 
 Rattier and Guibal, at Paris, and into which Hancock intro¬ 
 duced his process, the threads were either cut with a knife 
 from rubber sheet, or were produced by forcing a thick 
 paste of rubber in naphtha through apertures in an iron 
 plate, and allowing the naphtha to evaporate upon a surface 
 covered with French chalk. After the discovery of vulcaniza¬ 
 tion, and the possession of the English patent therefor by 
 the firm of Charles Macintosh and Company, the original 
 French method rapidly became obsolete, and in the fifties the 
 
172 
 
 INDIA-RUBBER. 
 
 resources of the Manchester factory were kept taxed night 
 and day to supply the demand that arose. The manufac¬ 
 ture, though involving no apparent difficulty, is yet one in 
 which considerable knowledge of detail is necessitated if 
 expensive mistakes are to be avoided ; moreover, workmen 
 capable of undertaking the dozen or more different opera¬ 
 tions involved are by no means easily to be picked up. 
 Owing to these circumstances, and also to the fact that the 
 profits .obtainable nowadays are hardly commensurate 
 with the risks involved, this branch of the trade has seen 
 less competition arise than is perhaps the case in any other 
 branch. In speaking of France, it ought to be said that the 
 manufacture of thread on modern lines was started a few 
 years ago, but is not now carried on, though the country still 
 remains prominent as a producer of elastic webbings, the 
 extent and artistic merit of these productions being amply 
 demonstrated by the exhibits at the last Paris Exhibition. 
 
 Elastic thread should, if properly made, stretch to seven 
 times its length without breaking. This of course neces¬ 
 sitates the use of the best quality rubber, and the onward 
 march of time has witnessed in this branch none of that 
 substitution of lower-grade material which has been so 
 much in evidence in many branches of the manufacture as 
 the result of competition. With elastic thread no tinkering 
 with the established practice of the past is permissible; it 
 would at once spell ruin, a fact which is acknowledged even 
 in Germany. Except in the case of the mineralized red 
 thread, produced by William Warne and Company, Limited, 
 of Tottenham, and which owes its colour and special pro¬ 
 perties to antimony sulphide, elastic thread is composed 
 exclusively of pure Para rubber and sulphur. Briefly 
 
ELASTIC THREAD. 
 
 17-3 
 
 summarised, the process of manufacture is as follows. The 
 rubber is dissolved, or “ let down,” to use a factory expres¬ 
 sion, in coal-tar naphtha to which the requisite amount of 
 flowers of sulphur has been added. The resulting “ dough ” 
 is then mixed to a homogeneous mass on immersing rollers 
 or in a pug mill. The next process is to spread the dissolved 
 rubber out into a sheet, and this was at one time always done 
 by means of a spreading machine similar to what is described 
 under the heading of “Waterproof Cloth.” Modern practice, 
 however, enjoins the use of the calender, whereby a 
 sheet of the required thickness, or “count,” is more 
 readily obtained, and at a less cost in naphtha. The cloth 
 on which the rubber sheet is spread, or rolled, as the case 
 may be, is surfaced with a material which enables the 
 rubber to be readily stripped therefrom when the naphtha 
 has been evaporated off by heat. In order to effect the 
 vulcanization the rubber sheet is stripped from the cloth 
 and put round a hollow iron drum, being inter-rolled with 
 cotton cloth in order to prevent adherence of the rubber. 
 This being done, the drum is lifted by a crane and put into 
 the vulcan pan and vulcanized in hot water, at 270° F. to 
 280° F., for a length of time which has to be accurately 
 gauged by the man in charge from his knowledge of the 
 composition of the rubber. Under-vulcanization or over¬ 
 vulcanization have both to be rigidly guarded against as 
 largely affecting the value of the finished thread. The 
 vulcanization completed, the rubber is unwound from the 
 cloth, pasted over with a solution of shellac in wood naphtha, 
 and tightly rolled upon a wooden drum. The shellac causes 
 the rubber to adhere closely and become, as it were, a rigid 
 block, in which state it is taken to the cutting lathes, 
 
174 
 
 INDIA-RUBBER. 
 
 where by means of rapidly-moving knives it is cut into 
 threads, which are of course the length of the original 
 sheet, say sixty-five yards. Elastic thread, it may be 
 mentioned, was first cut in lathes in 1849, by Charles 
 Macintosh and Company. The next operation consists 
 in boiling the roughly-skeined threads in a solution of 
 caustic soda in order to remove the shellac and the excess 
 of sulphur present. It is then well washed in water, dried 
 in a warm room, and stored in a dark place, after its elasticity 
 has been carefully observed by mechanical tests. There is 
 nothing calling for special mention in the lathes, and it will be 
 easily understood that it depends upon the gearing by which 
 the knife is controlled, and upon the thickness of the rubber 
 sheet, as to what count of thread is produced. The count, by 
 which term the dimensions of the thread are expressed in 
 the trade, represents the number which laid on one another 
 make an inch: thus, thirty-six, which is a common count, 
 means that each thread is one-thirty-sixth of an inch wide 
 and deep, it being almost universally cut in the rectangular 
 form. As regards the elastic webbing manufacture, Leices¬ 
 ter may be considered its headquarters in England, Derby 
 and Nottingham also being closely connected with the trade. 
 To follow the elastic thread to these towns would be to go 
 beyond the scope of this book, but reference may perhaps 
 be permitted to a point which closely concerns the interest 
 of the thread manufacturers. The author has heard of 
 numerous complaints in late years to the effect that elastic 
 webbing is of a poorer quality than it used to be. Enquiry 
 into this seems to make it clear that it is not the quality of 
 the rubber which is at fault, but rather its attenuation. In 
 other words, whether owing to competition or not, it has 
 
ELASTIC THREAD. 
 
 175 
 
 become customary to use finer counts than of old, and these 
 wear out sooner than the thicker counts, as is only to be 
 expected. Support is lent to this contention by the fact 
 that the prices of many classes of elastic webbing have been 
 reduced in late years. Quite a different way of accounting 
 for the occurrence of inferior webbing might possibly be 
 suggested by the old-established English firms. It is only 
 guess-work on the author’s part, but it is conceivable that 
 they put it down to the introduction of foreign-made thread 
 into the weaving factories of the Midlands, a development 
 of recent years which is not looked upon altogether with 
 complacency in Lancashire. 
 
 A new use for elastic thread arose a year or two ago in 
 connection with the rubber-cored golf ball, and considerable 
 quantities were sold for this purpose. In the latest practice, 
 however, this thread has been substituted by elastic ribbon 
 or tape similar to that used by electricians, except that it 
 is vulcanized. It is made from spread or rolled sheet 
 vulcanized and cut on lathes to about three-eighth inch 
 width. Judging by the rapid progress of events in the golf- 
 ball world of late years, this last item of intelligence may be 
 obsolete before this volume is published, but even if this 
 proves the fact, a reference to what is not generally known 
 is justifiable on the score of interest. 
 
 All users of elastic thread are familiar with the hard, brittle 
 nature of that which is worn out by oxidation. No doubt the 
 constant changes of temperature, slight though they may be, 
 which the rubber experiences, both in the ordinary process of 
 stretching and in the contact with the human body, tend 
 to shorten its life. As regards the weaving process, at 
 one time there used to occur wholesale cases of premature 
 
176 
 
 INDIA-RUBBER. 
 
 decomposition. These were attributable, doubtless, to the 
 use of a paraffin wax of too low a melting point as a lubri¬ 
 cant during weaving, and in some cases certainly to oxide 
 of copper in the black dye of the textile threads. As these 
 sources of trouble are now recognised and avoided, litigation 
 between the rubber manufacturer and the elastic-webbing 
 manufacturer only comes up for comment as a matter of 
 history. 
 
CHAPTER XIY. 
 
 THE MANUFACTURE OF MECHANICAL GOODS. 
 
 What are known in the rubber trade as “mechanicals,” 
 comprise a large variety of goods, the most important of 
 which, valves, buffers, washers, hose and belting, are used 
 in connection with machinery. The term is a convenient 
 one for rough classification, though it must not he read too 
 literally, as in accordance with trade-procedure goods will 
 here be included which in their particular applications do 
 not come within the purview of the engineer. Much of the 
 machinery employed is common up to a certain point for 
 all classes of goods. In all cases the rubber is compounded, 
 and in practically all it is vulcanized in one or another 
 form of pan or press. Probably in no two factories are the 
 details of procedure identical, the actual composition of 
 the batch of rubber and chemicals, or the “ mixing,” as it is 
 usually called, being regarded as a trade secret to be known 
 only to those immediately concerned. In order that this 
 secrecy may be preserved as far as possible, it is the general 
 rule not to allow foremen or workmen to roam into depart¬ 
 ments other than those in which they are specially engaged, 
 so that it may often happen that a man may be an 
 expert in half the manufacture of a particular article, and 
 be in ignorance of the remainder of the processes it has to 
 undergo. As a general statement, it will not be far from 
 
 I.R. 
 
 N 
 
ITS 
 
 INDIA-RUBBER. 
 
 the truth to say that there are very few real secret pro¬ 
 cesses in the trade to-day, though, as so much depends 
 upon close attention to detail, it is of little avail for a new 
 concern wishful of emulating a long-established one to 
 obtain a general description of a process. Unless the 
 fullest details are available, the proposed competition may 
 only result in loss to the instigator thereof, unless, 
 haply, fortune favours his guess-work. There is no intention 
 here to illustrate this precept by example from the pages 
 of history, as manufacturers generally will acknowledge 
 its truth. The rubber trade is not yet founded on such a 
 scientific and sure basis that the services of the practical man 
 who uses his experience can be dispensed with. Whether 
 it ever will be is matter for conjecture. Suffice it to say 
 that there is no immediate prospect of the practical man 
 who knows how to get certain results being -supplanted by 
 those who have not gone through the mill routine, what¬ 
 ever the scope of their scientific studies may have 
 been. But there are those who aver that chemistry ought 
 to take a much more important place in the manufac¬ 
 ture than it does. It is no use, however, shirking the 
 fact that the limitations of rubber analysis are a bar 
 to the service which the chemist can render the manu¬ 
 facturer. Chemistry has, of course, rendered many and 
 signal services to the trade, especially during the last 
 decade, but it has also failed in many directions where 
 great things were expected of it. But not to go at too 
 great length into generalities, what it is wished to empha¬ 
 sise is that in many cases it lies beyond the power of 
 the chemist to unravel the secret processes of the trade, 
 and that therefore the practical man who has worked these 
 
THE MANUFACTURE OF MECHANICAL GOODS. 179 
 
 processes, though probably without knowing the why and 
 the wherefore, must still be considered the most important 
 in the trade. It will be recognised at once that as long as 
 everything goes smoothly, rule-of-thumb working does not 
 call for condemnation ; when, however, as not infrequently 
 happens, some bad work is turned out, the operator is likely 
 to be quite at sea as to the cause, and as likely as not puts 
 the blame upon some innocent substance or operation. 
 The interests of the industry seem to demand that the 
 rule-of-thumb operator of the past and the present should 
 in the future be succeeded by one who combines a wide 
 experience of the details of the manufacture with a thorough 
 theoretical knowledge of the principles involved. A recent 
 author rates the india-rubber manufacturers of this country 
 for having as a class done little or nothing to develop the 
 scientific side, of their industry. 
 
 lo proceed with matters of fact rather than contro¬ 
 versy, the rubber and various chemicals, including sulphur, 
 for any particular “ mixing” having been carefully weighed 
 out, they have to be mixed together into a uniform mass. 
 This is done on the mixing rolls, which do not differ appre¬ 
 ciably in general appearance from the washing rolls. 
 Fig. 11 shows a pair of these rolls, and their character will 
 be understood by a few explanatory words. There are two 
 chilled iron rolls, about 3 feet by 16 inches in diameter. 
 The surfaces are smooth, and they are geared to move in 
 opposite directions at different speeds. They are hollow, so 
 as to allow of steam or cold water being circulated to keep 
 the rolls at the temperatures required for certain classes of 
 rubber or compounds. 
 
 Except in point of size and capacity, these mixing rolls have 
 
 n 2 
 
180 
 
 INDIA-RUBBEG. 
 
 undergone hardly any alteration since their inception about 
 seventy years ago, and they are in general use to-day. 
 Mention should, however, be made of the double-acting 
 three-cylinder mixing mill patented a few years ago by 
 J. T. Wicks, the use of which it is claimed reduces working 
 expenses, as the three-roll mill does twice the work of the 
 
 FIG. 11.—MIXING ROLLS. 
 
 two-roll, with the same cost for labour. Of course it is 
 more expensive, but the compensating advantages make 
 this a matter of no real importance in a large factory. Those 
 in use at the present time have rolls 48 inches long by 
 14 inches diameter. 
 
 In mixing a batch of compound, the workman places the 
 rubber on the rollers, which are adjusted apart, and it is 
 after a time formed into a sheet which adheres to the 
 
THE MANUFACTURE OF MECHANICAL GOOES. 181 
 
 slower-moving front roller; the various powders are then 
 gradually sprinkled on to the rubber and get incorporated 
 with it. From time to time the workman slits the rubber 
 sheet through with a knife, putting the several pieces 
 between the rolls to again be formed into a sheet. After 
 this process has been repeated a number of times, a per¬ 
 fectly homogeneous mass is obtained. In general terms, a 
 batch weighing about one cwt. will take thirty to forty 
 minutes, it being important that perfect homogeneity be 
 obtained in as short a time as possible, as over-working 
 tends to injure the rubber. 
 
 The operation known as “breaking down ” or “warming 
 up ” has for its object the restoration of plasticity to 
 washed rubber which has got rigid by being kept in stock. 
 This operation does not call for special mention, being 
 usually carried out on rolls similar in design to the 
 mixing rolls. We may now follow the batch of mixed 
 rubber to the calender, where it is rolled out into sheets 
 of greater or less thickness, according to the goods to be 
 made. The calender (Fig. 13) consists essentially of a system 
 of chilled iron rollers, two, three or four in number. Three 
 or four is the usual number, though some have been built 
 with as many as six rollers. Such multiplicity does not, 
 however, appear to have answered expectations, and the four- 
 roll calender may be taken as giving the maximum effi¬ 
 ciency in the purposes of its application. The rolls, like 
 those of the mixing mills, are hollow, to allow of the circula¬ 
 tion of steam or cold water as required ; their surface is 
 perfectly smootli, the main requisite of a high-class calender 
 roll, or bowl, as it is more commonly termed, being a 
 uniformly plane surface. The modus ojjeraudi is briefly 
 
182 
 
 INDIA-RUBBER. 
 
 as follows, and it will be readily understood by means of 
 Fig. 12 showing a three-bowl calender. 
 
 The workman having passed the compounded rubber 
 two or three times between rollers, places it in small 
 pieces at a time between the two top bowls marked 1 and 2. 
 It at once forms a thin sheet which adheres to the 
 bowl 2, and then passing between bowls 2 and 3 it is 
 rolled on to a sheet of calico which is being continuously 
 
 unrolled from the wooden roller or box marked 4. The 
 rubber and calico are then rolled up on the box marked 5. 
 The rolling up with calico is necessary in order to prevent 
 the layers from adhering to one another and becoming a 
 solid mass. If a solid cylinder of rubber is required, as 
 is occasionally the case, the rubber sheet passes from the 
 calender without being inter-rolled with calico. 
 
 Hose. —India-rubber hose is made of many different 
 descriptions and qualities according to the purposes for 
 which it is required. The enumeration of all the varieties 
 
THE MANUFACTURE OF MECHANICAL GOODS. 183 
 
 and a reference to their uses would occupy too much space, 
 so a selection will be made of those in most general demand. 
 
 FIG. 13. —FOUR-BOWL CALENDER. 
 
 Although hose is supplied by the manufacturers for specific 
 purposes, it is often put by the purchaser to uses for which it 
 is not ! intended or adapted. Thus the ordinary delivery 
 
184 
 
 INDIA-RUBBER. 
 
 hose is not intended to stand heat or acids, and if subjected 
 to them will accordingly prove defective. In steam-raising 
 the tendency of the age is to employ higher and higher pres¬ 
 sures, and the conditions under which rubber hose valves, 
 packings, etc., are used nowadays are, as a rule, much more 
 trying than was the case twenty years ago. Where the 
 rubber manufacturer is made fully acquainted with the con¬ 
 ditions of use he can so compound his rubber as to give the 
 best results possible. Of course, when no details are 
 furnished him, it is not surprising that unsuitable rubber 
 is sometimes supplied. Rubber hose is familiar enough on 
 the lawn and in the garden, and in Continental cities for 
 street watering. Large quantities are used by the railway 
 companies for vacuum and Westinghouse brakes, in which 
 connection its use is likely to be largely extended in the 
 near future, if the fitting of fast freight trains with power 
 brakes is made compulsory. For the steam heating of 
 passenger trains rubber hose is also largely in request. 
 Contractors use it in special forms, sometimes up to 3 feet 
 in diameter, for suction purposes ; while some fire brigades, 
 notably the Metropolitan, use rubber-lined flax hose instead 
 of ordinary textile hose. Brewers, again, use rubber hose, 
 specially prepared so that it shall not communicate any 
 taste or impurity to the beer. For a good many purposes 
 rubber hose has to be armoured, that is lapped externally 
 or internally with iron wire. In some cases this armouring 
 is embedded between the layers of rubber. The ordinary 
 hose for the vacuum-brake couplings is internally wired, so 
 as to prevent collapse by atmospheric pressure. External 
 wiring, in addition to a covering of marlin or hemp cord, 
 serves to protect hose used in rough work from damage. 
 
THE MANUFACTURE OF MECHANICAL GOODS. 185 
 
 Only in small-bore tubing for special purposes is rubber 
 used alone, in most cases canvas forming a prominent part; 
 indeed, in one or two cases the rubber is merely used in a 
 thin layer to make it water and air proof, flexibility being 
 of no moment. 
 
 In making up the hose hand-labour is mostly employed, 
 though a special lapping machine can be used, the calendered 
 rubber sheet, which is usually strongly compounded, being 
 cut in strips and rolled spirally round an iron mandril. On 
 this a layer of canvas is rolled. In the best work the 
 canvas is not used plain, but has had what is known as a 
 friction coat of rubber put on it by the calender bowls, 
 which for this purpose are set to revolve at different speeds. 
 The rubber is thus forced into the interstices of the canvas, 
 and its presence at the same time guarantees a perfect 
 contact between the textile material and the layers of rubber. 
 The making up of the hose having been finished, it is dusted 
 with French chalk, lapped in cloth, and is then ready for 
 vulcanization. A number of lengths of hose, which may be 
 40 to 60 feet long, are placed on a tray filled with French 
 chalk; the tray is put on a trolley and run into the 
 vulcanizing pan, in shape like an elongated boiler, of 4 feet 
 diameter. The lid having been closed and secured by bolts, 
 steam at about 40 lbs. pressure is turned into the jacket by 
 which the pan is surrounded or into the interior of the 
 pan. The time of vulcanisation depends on the quality 
 of the rubber, the amount of sulphur present and the 
 temperature, and may be anything from 40 minutes to 
 2 hours. 
 
 In the case of imbedded wire hose, the extra operation 
 of coiling the wire on to the soft rubber before the hose is 
 
186 
 
 INDIA-RUBBER. 
 
 completely made up is done by a machine. Where all- 
 rubber tubing of comparatively narrow diameter is being 
 made, the process is simpler, pieces of the mixed compound 
 rubber being fed into a machine of the type of a lead-pipe 
 drawing machine, with a mandril in the nozzle ; for a figure 
 of this, see under “ Cab Tyre Manufacture.” The tubing as 
 it emerges drops on a circular tray containing French chalk, 
 which slowly revolves, allowing the tubing to be deposited 
 concentrically. The tray is then covered with a lid or 
 sometimes left open, and is placed in a circular vulcanizing 
 pan to be cured in open steam. In the manufacture of 
 rubber-lined fire hose two or three different methods are 
 adopted, the most modern being to force the rubber com¬ 
 pound into the interior of the flax hose. Experience has 
 shown that the amount of working necessary to get the 
 best rubber sufficiently plastic for this operation has the 
 effect of shortening its life, 1 and a cheaper and more resinous 
 rubber is found to give equally good results in the end, this 
 not requiring to be masticated to the same extent before 
 being used. Rubber-lined fire hose, besides being heavier 
 than the unlined, is, of course, more expensive, and it may 
 be asked wherein do its advantages lie. The answer to this 
 is that by diminishing friction it enables the water to be 
 ejected at a higher velocity. From some figures obtained 
 by J. R. Freeman, an American authority, who experimented 
 on behalf of some insurance companies, it appears that 
 whereas ordinary canvas hose loses 27 lbs. pressure per 
 100 feet length, a smooth rubber-lined hose loses only 
 10 lbs., this particular test having reference to the discharge 
 of 250 gallons of water through a 2J inch hose. These 
 
 1 This is a point on which difference of opinion obtains. 
 
THE MANUFACTURE OF MECHANICAL GOODS. 187 
 
 figures are of interest, but it is important in tests of this 
 sort to note the quality of canvas hose used. In this test the 
 best quality may or may not have been used ; nothing is said 
 on this point. In the best quality fire hose, in which a fine 
 yarn is woven in a special way, there is likely to be less 
 friction than in common qualities. Naturally the rubber- 
 lined hose will not stand the same bursting pressure 
 as the unlined, but it will stand all that is likely to be 
 required of it. 
 
 Though principally used for small-diameter seamless hose, 
 the tubing machine referred to above is also utilised for 
 rubber tubing of larger diameter, which has been made from 
 sheet rubber doubled into cylindrical form. By passage 
 through the die of the machine the edges are firmly united. 
 
 With regard to railway hose, that which calls for most 
 notice is what is used for steam heating of passenger coaches. 
 The rubber for this purpose should be a special quality to 
 resist the continuous heat. Though a good deal has been 
 heard of the defection of this hose, the blame in many cases 
 is attributable to the way in which it is used. Enquiry has 
 revealed the fact that there is considerable difference of pro¬ 
 cedure on our railways ; in some cases steam at 80 lbs. to 
 100 lbs. pressure goes into the pipes, and in other cases it 
 is always passed through a reducing valve so as not to 
 exceed 40 lbs. Again, it is an open question whether more 
 damage is not done in the continual coupling and uncoupling 
 than by the steam; certainly this is the case on the hose of the 
 tender. The partial use of flexible metallic hose not having 
 been considered satisfactory, there is evidently no choice 
 but rubber, and this should be treated as fairly as possible. 
 That a great variation in the steam pressures admitted 
 
188 
 
 INDIA-BUBBEB, 
 
 exists, has been noticed by the author in a series of observa¬ 
 tions on steam beating on home and foreign railways, and 
 where guarantees are given with hose enquiry should be 
 made as to the conditions it is likely to experience. 
 
 Buffers, Washers, Rings, etc .—In making up these and 
 
 FIG. 14. —BELTING VULCAN PRESS. 
 
 numerous other articles the sheet from the calender is 
 unwrapped by machinery, the cloth going to one roller to 
 be used over again, and the rubber being rolled up over a 
 mandril to form a cylinder of the necessary dimensions. If 
 washers or rings are required the tube is wrapped in cloth 
 and taken to the vulcanizer. After being vulcanized the 
 outer cloth is removed, a mandril is inserted, and the tube 
 
THE MANUFACTURE OF MECHANICAL GOODS. 189 
 
 made to revolve in a lathe before a knife by which means 
 the rings are cut off. 
 
 In the case of buffers, these are cut off the unvulcanized 
 rubber, put into tightly-fitting iron moulds, and then vul¬ 
 canized. Valves are cut out of calendeied sheet, which has 
 been doubled or otherwise built up to the required thickness, 
 and then vulcanized. The valves are then cut out by means 
 of a vertical saw moving at high speed. Large buyers like 
 the Admiralty do this work themselves, buying the vulcanized 
 rubber in rolls from the manufacturers. 
 
 Rubber belting is made by spreading or calendering com¬ 
 pounded rubber on canvas sheet both sides, cutting this 
 into strips of the required width and building these up to 
 the necessary thickness. Vulcanization is effected in pi esses 
 the lower plate of which is made so as just to fit the belt 
 and to keep it under pressure during the process. Fig. 14 
 shows one of these belting presses. Many other goods 
 besides are vulcanized in presses, which in large works are 
 often worked by hydraulic power. Fig. 15 shows one of 
 these presses, which can be fitted with a screw stretching 
 arrangement, or for hydraulic power as required. In the 
 latter case an accumulator and steam pumps are required, 
 these not being shown in the figure. Sheet destined for valve 
 making may be vulcanized in these presses, or it may be 
 wrapped round a drum covered tightly with calico and vul¬ 
 canized in hot water in a manner similar to thread sheets. 
 Some manufacturers use one method, and some the other, 
 according to the light of their individual judgment. In the 
 press vulcanizers the plates are hollow for the admission of 
 steam, and they are usually lagged to prevent radiation. 
 It will be noticed that the rubber does not come into contact 
 
190 
 
 INDIA-RUBBER. 
 
 with the steam, but only with the steam-heatecl metal of the 
 press. Articles which are tightly fixed in separate moulds 
 are sometimes vulcanized in open steam; at other times in 
 
 FIG. 15.—SIX PLATEN HYDRAULIC VULCAN PRESS. 
 
 presses. These moulds, which form a considerable part of 
 the rubber manufacturer’s stock-in-trade, represent a large 
 capital outlay, and it is because of the expense involved 
 that manufacturers often show themselves averse to executing 
 
THE MANUFACTURE OF MECHANICAL GOODS. 191 
 
 small orders which require moulds not kept in stock. As a 
 rule the moulds are of iron only, hut for special purposes 
 they have a white metal lining. The exact temperature of 
 vulcanizing is a matter that requires close attention. On 
 the Continent the ordinary steam-pressure gauge is in 
 common use, while in England it is the general rule to use 
 the Fahrenheit thermometer ; this is put into a receptacle in 
 the lid of the vulcan pan or into the steam chamber of the 
 press, the receptacle as a rule having a small quantity of 
 mercury in it. Thermometers for the several purposes of a 
 rubber factory are specially made, and though there is no 
 need to go to the expense of a Kew certificate, it is desirable 
 to have them tested occasionally against a standard instru¬ 
 ment. Electrical recording arrangements and the recording- 
 drum aneroid have had trials, but owing to their expense 
 and liability to get out of order, together with the indifference, 
 if not active hostility, shown by under-managers and fore¬ 
 men towards new-fangled appliances, they have usually had 
 hut a short spell of life where they have been installed— 
 that is as far as the author’s own experience goes. In 
 America it is understood that recording instruments have a 
 wide application. Among one or two other goods which 
 space permits of mention we have rubber-covered rollers 
 for paper-making machines. In fixing these to the iron 
 roller it is customary to have a vulcanite layer next to the 
 iron, the soft roller being then vulcanized on to the hard 
 rubber. This class of work is somewhat difficult to execute 
 satisfactorily, as special means of attaching the vulcanite to 
 the iron have to be adopted. Certain British firms make a 
 speciality of these rollers, but the entry of Sweden into 
 rubber manufacturing has already led to Swedish rollers 
 
192 
 
 INDIA-RUBBER. 
 
 being used instead of British in Scandinavia, at any rate in 
 the paper-works in the North of Norway visited by the 
 author. 
 
 A new article, the manufacture of which in the last two 
 or three years has assumed imposing dimensions, is the 
 rubber heel-pad. They are now made by the million, and 
 call for a greater or less amount of rubber according to the 
 quality. The manufacture is a simple one, consisting of 
 stamping out the heels from compounded rubber, which 
 need not have been calendered, and vulcanizing in steam in 
 moulds holding a dozen or more heels each. They are 
 also vulcanized in hydraulic presses. There are many 
 so-called patent heels, sold by firms who get them made 
 under contract at the rubber works, the particular shape 
 and marking being given to the heels by the moulds during 
 vulcanization. Though these heels can be bought of best 
 quality, combining elasticity and resistance to abrasion, so 
 many of a low quality have been made of late that the 
 reputation of the goods generally is bound to suffer 
 eventually, if, indeed, this is not already the case. Rapidity 
 of ouput is a feature of this branch, and the rubber mixing 
 is arranged so as to occupy only about a quarter of an hour or 
 twenty minutes in vulcanizing. To give some idea of the 
 magnitude this business has attained, it may be mentioned 
 that the Wood-Milne Company, who first put the heels on 
 the market in 1896, now have a yearly output of over 
 twenty million pairs. 
 
 India-rubber packings for piston rods, gauge-glass rings, 
 etc., etc., do not at the present time enjoy the popularity 
 they once did. Two main reasons may be adduced for 
 this—firstly, the low quality of the rubber, which resulted 
 
THE MANUFACTURE OF MECHANICAL GOODS. 193 
 
 fioni competition and a desire for cheapness on the buyers’ 
 part; and secondly, from the increasing use of higher 
 steam pressures, for which rubber was found less suitable 
 than other materials. Asbestos has now largely replaced 
 lubber, being used either alone or wrapped round an india- 
 rubber core. There is the competition, also, of various 
 other materials, such as vulcanized fibre and numerous other 
 proprietary articles, each of them claiming to be superior 
 to the others for use with high temperatures. In such 
 packings the bulk of the material is naturally heat-resisting, 
 only a small proportion of rubber, or in some cases balata, 
 being used to give flexibility and to act as a cementing 
 material for the mineral matter. America may be credited 
 with the lead in modern high-pressure steam packings, 
 though of late European firms have taken a leaf out of 
 America’s book, and gone a long way towards supplying 
 their own requirements. The metallic packing, first 
 mtioduced fiom America, is now made in Great Britain, 
 but although it has decided advantages over rubber, asbestos, 
 etc., especially in locomotive and marine work, its high price 
 has caused it to lag behind in popular favour. The name 
 of “ Tuck ” is so well known in connection with packings 
 that it is now used as a generic term by Continental 
 manufacturers, and it must no longer be assumed that all 
 packing called “Tuck” has emanated from the Lambeth 
 works. From what has already been said about vulcaniza¬ 
 tion, it will be at once understood that vulcanized rubber 
 packing, in contact with heated surfaces, will become over¬ 
 vulcanized and hard. In order to obviate this as far as 
 possible it has been sent out decidedly on the soft side, 
 vulcanization being completed when the packing is m use. 
 
 I.R. 
 
 O 
 
194 
 
 INDIA-RUBBER. 
 
 As in the case of rubber hose, it is always desirable for the 
 manufacturer to have some detailed information as to what 
 the packing is wanted for, and he will then be in a position 
 to supply what will give the best results. To comment on 
 the various uses of engine packing would occupy too much 
 space, besides being somewhat beyond the scope of this 
 volume, which is primarily concerned with the nature and 
 manipulation of rubber. 
 
 With regard to the manufacture of india-rubber packing, 
 there is no special machinery required, and the making up 
 does not call for more than a word or two of explanation. 
 As in hose manufacture, the textile material has a rubber 
 coating put on it by the friction calender, and this is made 
 up on a rubber core to either round or square section. In 
 the case of very cheap packing the textile used, often old 
 hempen sail-cloth, will not stand frictioning, and has to be 
 coated on the spreading machine. The packing, after being 
 made up in lengths, is vulcanized either in the press or pan. 
 With regard to the textile material used, there is really no 
 object in using first-class quality, because cotton begins to 
 tender at 280° F., a fact which, in modern times, has led 
 to the substitution of woven asbestos, which can he coated 
 with rubber on the spreading machine. For certain 
 purposes metallic gauze is also introduced into the asbestos. 
 In an Admiralty specification for a special packing of this 
 composite nature, an alloy of lead and tin is used, in which 
 the tin present must not be below 10 per cent. 
 
 In addition to the belting used for machine driving, 
 rubber belts of large size are employed as conveying or 
 picking belts in grain elevators, there being one of these 
 in the United States three miles in length. As picking 
 
THE MANUFACTURE OF MECHANICAL GOODS. 195 
 
 belts they are used in metal mining, and in the ore- 
 concentrating machine known as the Frue vanner, a 
 rubber belt four or five feet w 7 ide forms the huddling sur¬ 
 face. For the purpose, however, of ore concentration the 
 rubber-belt machine finds a severe competitor in the 
 Wilfley table, in which the rubber surface is replaced by 
 linoleum, and there is the less inducement for English 
 manufacturers to compete in a business so largely monopo¬ 
 lised by the American rubber firms. All the same, as the 
 revival of tin mining in Cornwall on modern lines is 
 proceeding apace, the Frue vanner may be expected to 
 reign in the place of the round huddle of old memory, and 
 home manufacturers should see that their own inaction is 
 not the cause of the necessary rubber fittings being- 
 imported. A new form of belting is that recently patented 
 by Redd away and Company especially for machine driving- 
 in damp climates. This is the ordinary woven cotton and 
 hair belting, with a layer of vulcanized rubber on each side, 
 the absorption of moisture being thus effectively prevented. 
 
 Rubber 1 ’avem ent .—The rubber pavement recently put down 
 at the Savoy Hotel, London, at a cost of £2,000, has drawn 
 renewed attention to a use for rubber which was initiated 
 thirty years ago. In 1875 rubber pavement was put down by 
 Charles Macintosh and Company, at the Midland Grand 
 Hotel, and also at Euston Station in J881. Although worn 
 parts of the latter have recently been relaid, the suitability 
 of the material for resisting wear and tear, and at the same 
 time acting as a noise-deadener, must be considered amply 
 proved. Certainly a critic correctly points out that so far 
 such pavements have only been used under a roof, and that 
 the bulk of the vehicles passing over it have been rubber 
 
 o 2 
 
196 
 
 INDIA-RUBBER. 
 
 tyred. These points rightly call for consideration by those 
 who are contemplating putting down rubber pavement 
 under more severe conditions, but they are by no means 
 conclusive evidence against the prospective longevity of 
 such pavement for street use. It may naturally be expected 
 that the wear and tear will bear some definite ratio to the 
 amount and severity of the traffic, points on which reliable 
 data are yet wanting. Of course, with rubber at its present 
 price, the general use of rubber pavement is out of the 
 question, though investors in rubber plantations, fearful of 
 over-production ten years hence, profess to see in the rubber 
 pavement a guarantee of sustained dividends. Somewhat 
 allied to the pavement is the rubber flooring, which, in the 
 interlocking pattern, has recently attracted some attention. 
 In connection with this development the New York Packing 
 and Belting Company have been to the fore in America, 
 and we shall probably see it replacing linoleum in England 
 to some extent before long. 
 
 Rubber stair treads and mats have long been known. Of 
 late the demand for the latter has shown an increase, and 
 the quality of the rubber has been improved. Twenty 
 years ago it was a commonplace tale that the Saturday 
 sweepings in the rubber factory went into perambulator 
 tyres and door mats in the following week. There was 
 exaggeration no doubt in this, but still the quality of the 
 rubber formerly used was undeniably low. In making these 
 mats the holes are machine or hand punched out of 
 calendered sheets built up to the required thickness, vulcani¬ 
 zation being effected in the hydraulic press. Other mats 
 are moulded, taking their form from the vulcan press 
 plate. 
 
THE MANUFACTURE OF MECHANICAL GOODS. 197 
 
 Rubber Soles for lawn-tennis shoes are commonly classed 
 among mechanical goods, their manufacture being carried 
 on in ordinary rubber factories, and not specially by those 
 who make goloshes. The rubber sole is of very varying 
 composition and quality according to price. The manu¬ 
 facture is carried out on similar lines to that of heel pads, 
 an excess of sulphur being generally used in order to ensure 
 rapid vulcanization ; in fact, it is not uncommon for three 
 charges to be turned out in one hour from the same vulcan 
 press. The wearing surface is either plain or corrugated 
 according to the mould used in the vulcanization. These 
 soles may be stitched on to the leather sole in addition to 
 being cemented with rubber solution, though the stitching is 
 frequently omitted as being superfluous. Although no facilities 
 are offered by the retail trade for replacing worn soles by 
 new ones, the uppers of a good tennis shoe will always 
 stand two if not three soles, and those who have an eye to 
 economy would probably find no great difficulty in getting 
 new soles put on at the rubber factory at a cost considerably 
 less than that of a new pair of shoes. Of course, a pair of 
 soles might be purchased and put on the shoes at home 
 with rubber solution, but unless the operator possesses some 
 degree of technical knowledge this procedure is not to be 
 recommended. 
 
CHAPTER XV. 
 
 SUNDRY RUBBER ARTICLES. 
 
 Under this non-committal title it will be convenient to 
 refer to some rubber goods of more or less general interest 
 which do not call for a chapter to themselves. 
 
 Hollow Balls. —Lawn-tennis balls and playing balls, both 
 plain and coloured, form a branch of the trade limited to 
 only a few firms, who do the business on a large scale. It 
 is essentially a season business, particularly in the case of 
 lawn-tennis balls, the ball department being worked at full 
 pressure from January to June, while during the rest of the 
 year things are very quiet. In making a lawn-tennis ball 
 the compound sheet rubber is cut into oval pieces accurately 
 with a knife and metal shape, a bevelled edge being given 
 to facilitate subsequent adhesion. Two or four of these 
 pieces, according to their form, are joined together by 
 pressure on the edges, and before quite closing up, a small 
 piece of pure rubber is stuck to the inside, its position being 
 shown by a mark on the outside. A little ammonium 
 carbonate is then put inside the ball, and the aperture 
 made up. The hall is then put into an iron mould and 
 vulcanized in steam. After this process, in which it is kept 
 inflated by the dissociation of the solid ammonium carbonate 
 into gas, it is permanently blown up by compressed air, the 
 sharp nozzle of the blower being inserted at the point where 
 
SUNDRY RUBBER ARTICLES. 
 
 199 
 
 the piece of pure rubber is enclosed in the ball, the object 
 of this being to ensure the closing up of the hole made by 
 the nozzle of the blower directly the latter is withdrawn. 
 
 Another process of making balls replaces hand by machine 
 labour. This process, which employs the machine patented 
 by Cox, was in regular use for some years by the Eccles Rubber 
 Company. It is certainly economical in labour, but requires 
 a better class of rubber compound than that which is 
 usually associated with the ball trade, and when the better 
 rubber is used the saving on labour is neutralized. Perhaps 
 this statement ought to be qualified by the remark that 
 taken all round the quality of the hand-made ball does not 
 usually fall below that with the working of which the Cox 
 machine can show economies. Cox’s machine was not the 
 first attempt to minimise hand labour in ball making, as it 
 was not patented until some years after Hide’s patent 
 machine had been in operation at the Eccles Works. In 
 the latter machine two segments of rubber were formed 
 into a ball in the mould, while in Cox’s the ball was formed 
 from a single piece, but its advantage over the earlier 
 patented machine lies in its capacity for producing a 
 properly inflated ball. 
 
 Hollow playing balls are usually made from four segments, 
 in a manner similar to that described above. 
 
 Hollow balls maybe classified in three divisions, ordinary 
 grey balls of varying diameter, the same coloured by hand¬ 
 painting, transfer pictures, etc., and lawn-tennis balls. The 
 hand-painting does not call for such artistic merit as we 
 find in the pottery trade, but an apprenticeship of some 
 duration is required to do the work neatly and expeditiously. 
 The most important class is the lawn-tennis ball, this 
 
200 
 
 INDIA-RUBBER. 
 
 having to satisfy specific requirements of weight, size and 
 “ bounce.” After vulcanization they are covered with two 
 segments of felt, which dovetail one into the other ; a little 
 rubber solution ensures the adherence of the felt to the ball, 
 though in addition it is necessary to sew the seams. Large 
 numbers of these balls are sold in the uncovered condition 
 to other firms, who do the covering and put them on the 
 market. It is somewhat of an anomaly that the demand 
 for hollow balls is nearly always in excess of the supply, 
 and it might be thought that the few firms in the business 
 would have met with competition. The fact that the trade 
 is so largely a season one, however, no doubt deters many 
 who wish their capital to be employed all the year round. 
 Besides, there is the ever-present bugbear of German 
 competition, balls being sold in Germany at a price which 
 allows of any surplus being sold here at what must be an 
 actual loss. It may be mentioned that the British and 
 German producers now meet once a year to decide on 
 prices, though there is nothing in the nature of a cartel 
 or trust. 
 
 The Rubber Sponge .—This article, which has attained 
 prominence and a considerable degree of popularity in 
 Great Britain within the last few years, was until quite 
 recently a monopoly of the Russian-American Rubber 
 Company, of St. Petersburg, and a large number, if indeed 
 not the bulk, of those seen in the shop windows in England 
 bear a label inscribed in Russian characters. The mystery 
 attending the manufacture has been dispelled by some 
 German and American firms, who are now in competition 
 with the Muscovite kingdom, but the author is not aware of 
 any British firm having yet succeeded in following the 
 
SUNDRY RUBBER ARTICLES. 
 
 201 
 
 Russian lead. In the rubber manufacture generally, as 
 will have been gathered from preceding chapters, porosity 
 is an enemy to be specially guarded against, the 
 presence of moisture in the ingredients of a “ mixing ” 
 having a potent and generally sinister effect. In the case 
 of sponge rubber porosity is just what is wanted, but there 
 seems to be a decided difficulty in getting enough of it when 
 you want it as a would-be manufacturer once remarked. 
 There is no demand as yet for a sponge that will take the 
 place of pumice stone, a material to which some of the 
 experimental work done may be fitly compared as far as 
 hardness is concerned. By the way, it is interesting to note 
 that one author states the rubber sponge is of British 
 origin. 
 
 Surgical Goods .—With regard to this branch references 
 have been made elsewhere to topics of general interest, and 
 there are no special processes of manufacturing which 
 demand attention. In some instances there is as much 
 delicacy required in production, as there is in talking about 
 them, and a few generalities will perhaps suffice for the 
 purpose of this volume. Hollow articles of compounded 
 rubber are fashioned by hand, and, a pinch of ammonium 
 carbonate having been added, are vulcanized in iron moulds 
 in the same manner as hollow balls, a longer time being 
 required owing to the thickness of the rubber. Where the 
 compound rubber is required to be black, lamp black is 
 used, lead compounds being barred as likely to lead to 
 trouble. For red rubber the pentasulphide of antimony is 
 used, oxide of zinc being the principal “ filler ” in white 
 rubber. Gloves finger tips and many other articles are 
 made up of pure sheet, and are vulcanized in two or three 
 
202 
 
 INDIA-RUBBER. 
 
 different ways. A special feature appertaining to surgical 
 goods is the enamel, for which the several firms have their 
 own formulae. This has to be made so that it will not 
 crack off, a result which has been attained with varying 
 degrees of success by firms engaged in this branch. Bubber 
 forms a component part of this enamel, and vulcanization 
 is usually effected by dipping in the cold cure solution. 
 
 Stationers’ Goods .—Erasing rubber calls for mention, if 
 only as the first rubber article sold to the public. The 
 original form in which this came into commerce was a 
 piece cut from the raw Para rubber, and although such is 
 still to be met with in drawing offices, that which is usually 
 sold at the present time is vulcanized rubber, mostly in the 
 heavily compounded form. A prominent firm in this con¬ 
 nection is the Bavarian house of Faber & Co., having also 
 large factories in America. The rubber department is, of 
 course, only an accessory to the rest of the business with 
 which the name of Faber is associated, but in itself it is 
 large enough to warrant this special reference. 
 
 Bubber bands like thread require the quality of elasticity 
 in its supremacy, and the mineral matter the well known 
 red bands contain is limited to the pentasulphide of anti¬ 
 mony, to which they owe their colour. In the manufacture 
 the rubber mixed with antimony sulphide and sulphur is 
 put through the tubing machine, and the resulting tube 
 having been vulcanized on a mandril in open steam, is cut 
 into bands by lathes. The excess of sulphur is then 
 removed by boiling in a solution of caustic alkali. The 
 vulcanization must be timed very exactly if the bands are 
 to preserve their elasticity; if overdone they will go hard 
 in a short time and break under tension. The boiling in 
 
SUNDRY RUBBER ARTICLES. 
 
 203 
 
 alkali, usually caustic soda, lasts for three or four hours, 
 and it is important that the liquor should be clean and not 
 contain too much sulphide of sodium, resulting from pre¬ 
 vious use, a remark of general application in the desulphuri¬ 
 zation of vulcanized rubber goods. 
 
 Dental and Stamp Rubber .—Rubber compounds for these 
 purposes are prepared in the factories and sold in the 
 unvulcanized state to be vulcanized when they have 
 received the shape in which they are destined to remain 
 permanently. Although there are one or two firms in 
 Great Britain making a speciality of dental rubbers, these 
 are more extensively made in the United States from 
 formulae which are not very generally known. The manu¬ 
 facture has more reference to vulcanite than soft rubber, 
 and it is important for the dentist to be able to depend 
 with confidence upon the composition of the rubber for 
 which he pays such a high price. Oxide of zinc, sulphide 
 of zinc, and vermilion are chemicals largely used in these 
 rubbers, into which it is important that nothing of a 
 decidedly poisonous nature should enter. The methods of 
 moulding in plaster of Paris and vulcanization in steam, 
 although performed in special apparatus, do not differ in 
 principle from what has already been mentioned, and those 
 who are especially interested may be referred to books on 
 dental surgery. Dental dam, or rubber sheet, is usually 
 pure spread sheet vulcanized, though the vulcanized cut 
 sheet is also used to some extent. It is advisable that first 
 quality sheet only should he used for this purpose, the 
 normal terrors of the dentist’s chair being quite sufficient 
 without the added objection of sucking oil substitutes. The 
 vulcanization of dental dam is sometimes effected by 
 
204 
 
 INDIA-RUBBER. 
 
 chloride of sulphur vapours, and in the case of spread 
 sheet which has been mixed with sulphur, steam vulcani¬ 
 zation is employed. The surface is sometimes sprinkled 
 with aluminium powder, the idea being to give a reflecting 
 surface to aid the operator. By way of stiffening the com¬ 
 pound dental rubber, a recent patent of the Dental 
 Manufacturing Co., of London, has reference to the inser¬ 
 tion of fine nickel wire gauze within the rubber. Although 
 it may be new to use nickel for this purpose, it is interesting 
 to note that over twenty years ago platinum gauze was 
 used. At the present price of platinum, A'8 per ounce, 
 double that of gold, it is not surprising that it has been 
 sought to use a less costly metal for a purpose where the 
 special properties which make platinum so valuable do not 
 come into consideration. 
 
 Bottle Bings .—Rubber rings, commonly called Codd’s 
 rings, are largely used for beer and aerated water bottles, a 
 special ring being also made for fruit jars. For these pur¬ 
 poses a demand is made on the rubber which is practically 
 unknown with regard to the bulk of .goods manufactured. 
 It is required that the rubber rings be as far as possible 
 odourless, and in order to fall in with this suggestion 
 certain brands of rubber have to be rigidly tabooed. If 
 price were no object the desired end could be satisfactorily 
 attained by the use of the best Para rubber, but unfortu¬ 
 nately the conditions of business rarely permit of this, and 
 so various expedients have been resorted to in order to 
 remove the smell of inferior rubbers. Very little success 
 has, however, been attained in this direction, and for 
 reasons which seem pretty obvious. Although pure rubber 
 has an odour sui generis, this is by no means powerful or 
 
SUNDRY RUBBER ARTICLES. 
 
 205 
 
 disagreeable, and what trouble there is about the smell 
 may be put down principally to the albuminous matters 
 which in small quantities remain in the washed rubber. 
 Various oxidizing agents will destroy the smell for a time, 
 but owing to the fact that the action is only superficial, the 
 remedy proves to be but temporary, and the trouble soon 
 arises again. It must not be taken that the use of oxidizing 
 agents is advocated as desirable; indeed, grave suspicion 
 attaches to any such procedure, because there is every 
 probability that what will destroy the albuminous matter 
 will have an injurious action upon the rubber also. What 
 is known as Bourn’s process for deodorizing rubber goods 
 is based on safer lines. This consists in placing the goods 
 in trays of charcoal in a warm stove. Although, however, 
 this is referred to by previous writers as a process of value, 
 the author has never found it to come up to expectations, 
 that is, with regard to permanency of result. As in the 
 case of oxidizing solutions, the undoubted deodorization which 
 is at first effected soon gives place to the old state of affairs. 
 
 To turn to another point connected more particularly 
 with fruit and salmon jar rings, it is important that the 
 rubber be prepared especially to withstand, in the first 
 case, vegetable acids, and in the second case, oily sub¬ 
 stances. This is a matter which has closely engaged the 
 attention of the manufacturers with satisfactory results, 
 and it need hardly be said that in view of the possible 
 action of the contents of the jars upon the rubber, the use 
 of certain metallic oxides, harmless enough for other goods, 
 has been recognised as undesirable. Although in some 
 quarters the use of rings made of asbestos, felt, or other 
 material has been advocated in the interests of hygiene, it 
 
206 
 
 INDIA-RUBBER. 
 
 does not seem to have been proved that the slightest 
 danger need be apprehended from rubber rings where these 
 are of a quality suited for the purpose. While on this 
 question of hygiene a word or two may be said with refer¬ 
 ence to the charge brought against beer bottle rings a year 
 or two ago, to the effect that they had a good deal to do 
 with the spread of a certain fashionable disease. It was 
 contended that the red sulphide of antimony, which such 
 rings usually contain, either went into solution or separated 
 out as a powder at the bottom of the bottle, and that in 
 either case it led to the specific trouble. The statement 
 that the antimony goes into solution may he dismissed as 
 baseless, though, with regard to the sediment at the bottom 
 of the bottle, it may be taken that it consists of particles of 
 rubber, and not of separated mineral. Certainly any such 
 sediment is decidedly objectionable, but it would be caused 
 just the same if antimony were not used, if old decayed 
 rings were retained in use. No doubt sufficient care has 
 not always been taken to see that decayed rings are replaced 
 by new ones, and if this is remedied the commotion caused 
 cannot be considered as altogether superfluous. Of course 
 the use of antimony sulphide as a vulcanizing and colouring 
 agent is not absolutely essential, and it could be dispensed 
 with if the indictment brought against it could stand the 
 test of cross-examination. 
 
 India-rubber gloves have long been used by surgeons, 
 but of late years a greatly increased demand has arisen in 
 connection witli electrical engineering. In a recent trial 
 the judge expressed surprise that the use of such gloves by 
 men engaged in dangerous electrical work is not com¬ 
 pulsory, and it was suggested that the matter required 
 
SUNDRY RUBBER ARTICLES. 
 
 207 
 
 legislative intervention. Quite a number of improvements 
 have of late been suggested in connection with these gloves, 
 the important matter of ventilation coming up for particular 
 notice. The ordinary surgical rubber gloves are usually 
 made from cut sheet rubber, the joints being secured by a 
 narrow strip of rubber solutioned on, vulcanization being 
 effected in the sulphur bath. A different process is followed 
 by the Lindsay Rubber Co., of New York; in this the 
 glove is made in the seamless state from rubber solution, 
 being built up of two or three layers, some of pure and 
 some of compound rubber. 
 
 An insignificant article, the umbrella ring to wit, is made 
 in such large quantities that it is really surprising where 
 they all go to. As strength is a prominent requisite 
 in these articles, they are all made up by hand after a par¬ 
 ticular manner, of which the following is a brief description. 
 Strips of spread sheet, consisting of pure rubber and sul¬ 
 phur, are cut into short lengths with oblique ends, giving 
 the form of an elongated lozenge. These are wrapped 
 round a mandril, and the edges firmly pressed together to 
 form a perfect tube, in which the line of junction takes an 
 oblique direction. The workgirl then rolls the tube back¬ 
 wards and forwards with her fingers until it takes the form 
 of a ring, in which the original jointing line forms part 
 and parcel of the rubber mass so perfectly that it does not 
 constitute an inherent source of weakness. The rings are 
 subsequently laid in a tray of French chalk, and vulcanized 
 in the steam pan. 
 
 The vacuum jar ring, which, like the umbrella ring, has 
 a circular cross-section, is made by a less laborious process. 
 As it has not to undergo tension when in use, the strength 
 
208 
 
 INDIA-RUBBER. 
 
 of the joint is not a matter of great importance, and the 
 rings are made from cord rubber, which has been produced 
 in the tubing machine. A piece of the cord has its ends cut 
 obliquely and joined up by pressure, vulcanization being 
 effected in steam on a bed of French chalk. 
 
 India-rubber Toys .—The great bulk, if indeed not all, of 
 the galaxy of the rubber toys coloured or plain which are 
 to be seen in the shop windows come from the Continent, 
 France and Germany having long been the principal pro¬ 
 ducers, though Russia has recently entered the field. The 
 business has never recommended itself to the large British 
 and American factories: for the weight of rubber turned 
 out, there is a good deal of trouble in providing a variety of 
 moulds, the toys all being made of compounded rubber and 
 being shaped and vulcanized in specially designed moulds. 
 The French seem to have started the manufacture first, 
 possibly getting the idea from the animal and other shapes 
 in which the Para rubber of the early days of the industry 
 was exported. In 1876 some commotion was caused in 
 Germany by the death of a child from sucking a rubber toy 
 imported from France, and the German doctors having 
 discovered that zinc oxide was poisonous, got a decree 
 passed forbidding the importation of French rubber toys 
 into Germany, The French saw in this an adroit move on 
 the part of the Germans to efface competition, and they 
 were not wrong, for the manufacture was shortly started in 
 Germany without any particular attention being paid as to 
 what chemicals were used. Meanwhile, the French Minister 
 of Agriculture and Commerce appointed a committee, who 
 found that zinc oxide was perfectly harmless, but that 
 several of the colours used in painting the toys were 
 
SUNDRY RUBBER ARTICLES. 
 
 209 
 
 poisonous. Of these colours, white lead, Prussian blue, 
 Scheele s green (arsenite of copper), chrome yellow and 
 vermilion were barred from further use on toys by a decree 
 ot’ the Prefect of Police in 1878, and although some modifi¬ 
 cation was made in a further decree of 1884, it may he 
 taken that poisonous colours are not now to be met with on 
 French rubber toys, and in this respect the law is now 
 much the same in Germany. In the latter country, more¬ 
 over, although the indictment of zinc oxide has been aban¬ 
 doned, it is forbidden to use lead oxides, barytes, or other 
 more or less poisonous chemicals in the body of the rubber. 
 
 Rubber in the Chemical Laboratory. —India-rubber corks 
 and gas tubing are in common use by the analyst, and a 
 word or two about them may not be without interest. The 
 original rubber cork consisted of natural cork, either treated 
 with rubber solution or having a film of sheet rubber 
 attached to its surface. These belong to the domain of 
 history, laboratory corks of the present time consisting of 
 compound rubber vulcanized in moulds, the red ones con¬ 
 taining antimony pentasulphide being the best quality. 
 Periodically, some chemist writes to the Chemical News or 
 other journal drawing attention to the fact that he has 
 discovered free sulphur in these corks and that it may 
 easily lead to errors in work. This is certainly the case, 
 and where these corks are used in extraction apparatus 
 with alcohol, acetone or other sulphur solvent, the precau¬ 
 tion of boiling them in caustic alkali should always be taken. 
 Constant exposure to high temperature will cause hardening 
 and decay after a time, while the vapours of ether and 
 hydrocarbons will induce swelling and subsequent disinte¬ 
 gration, which may cause particles of mineral matter to be 
 i. a. 
 
 p 
 
210 
 
 INDIA-RUBBER. 
 
 removed. Examination should, therefore, be made from 
 time to time and defective corks he replaced by new ones. 
 
 With regard to rubber gas tubing, this is sold at prices 
 to suit all purses, though it must be confessed that the sale 
 of tubing containing so much mineral matter that it will 
 hardly bend is a practice that calls for strong disapproba¬ 
 tion. Fires, and in one case at least loss of life, have 
 resulted from such tubing breaking from its connection 
 with the gas supply. The very best, and of course the 
 most expensive, tubing is made of Para rubber and sulphur 
 only ; this, after being desulphurized, is almost black in 
 colour. Perhaps of equal merit is the red tubing containing 
 only pentasulphide of antimony as mineral matter. The 
 black tubing is sometimes vulcanized in the sulphur bath, 
 and occasionally in the bisulphide of carbon and chloride of 
 sulphur liquor, though the latter process is much too risky 
 to be recommended. These processes are only employed 
 when tubing is made from pure sheet rubber by joining up 
 the edges of a strip over a mandril. Although the greatest 
 flexibility is shown by the purest rubber, experiments 
 have shown that with regard to the passage of coal gas 
 through the pores of the rubber, the compounded rubber 
 acts better than the pure. It has been mentioned elsewhere 
 that rubber will transmit gases, and it is not difficult to 
 appreciate that mineral matter in moderate quantity will 
 lessen the tendency of coal gas to diffuse through rubber 
 tubing. 
 
 Hot-water Bottles .—A recent assize trial in which damages 
 were claimed by a patient for injury received from the 
 bursting of a rubber hot-water bottle, brought this article 
 into prominence. Without going into the details of the 
 
SUNDRY RUBBER ARTICLES. 
 
 211 
 
 case, it was made apparent from the analysis of the rubber 
 that it was of very inferior quality, though this, of course, 
 might not have been within the cognisance of the unfor¬ 
 tunate chemist who was mulcted in damages. It has been 
 urged in another chapter that the cheapening of rubber 
 goods, owing to competition, is a most reprehensible practice 
 in the case of medical requirements, where any defection 
 may be attended with momentous consequences. The 
 defective bottle in the case mentioned was no doubt worth 
 the money paid for it, but, being sold as a hot-water bottle, 
 it carried an implied though probably not expressed warranty 
 that it would stand hot water. Not unnaturally, the sequel 
 to the case mentioned has been the demand by the 
 retailer of a warranty from the manufacturer, a demand 
 which is readily complied with where the purchaser is 
 willing to pay for good quality material and not an article 
 produced at cut prices. Pure rubber is by no means called 
 for ; a considerable amount of mineral is admissible, but the 
 rubber present must be of sound quality. There is nothing 
 which calls for special notice in the manufacture; the 
 cotton cloth faced with rubber on both sides on the spreading 
 machine is cut into pieces of the necessary shape and jointed 
 with strong bands of the same material. When the naphtha 
 of the jointing solution has quite evaporated, the bottles are 
 put into a tray containing French chalk and vulcanized in 
 the steam pan. They are also vulcanized sometimes in the 
 dry heat chamber, but whatever process is adopted, pre¬ 
 caution must be taken not to “tender” the fabric, as it is 
 on this that the power to withstand the pressure of the hot 
 water depends. An excess of sulphur in order to promote 
 rapid vulcanization is no drawback to the finished goods, 
 
 p 2 
 
212 
 
 INDIA-RUBBER. 
 
 more especially when they have a loose outer cover of textile 
 material put on them. 
 
 A ir 'proof goods, such as invalid beds and cushions, are 
 still made after much the same manner as in Hancock’s 
 time. It is the exception, rather than the rule, to vulcanize 
 the rubber, which is composed of about ten coatings of Para 
 rubber put on the cotton cloth on the spreading machine. 
 
CHAPTER XVI. 
 
 INDIA-RUBBER PROOFED TEXTURES. 
 
 As we have seen in the introduction, the art of water¬ 
 proofing cloth with rubber formed the subject of some of 
 the earliest patents in connection with the trade, the earlier 
 attempts in this direction being improved by Macintosh to 
 such an extent that his double texture waterproof cloth 
 came into very general use. The machinery, however, used 
 for the first fourteen years in the Manchester factory was 
 by no means efficient, and a great advance was made when 
 Hancock patented his spreading machine in 1837 . The 
 machine in ordinary use at the present time differs only in 
 some points of detail from that patented by Hancock, and 
 only three modifications of it have been introduced of recent 
 years which call for notice. The rationale of the spreading 
 process, expressed in a few sentences, is as follows :— 
 
 The cleaned rubber, either pure or mixed with sulphur 
 and mineral matters, according to the purpose for which it is 
 required, is rolled out into very thin sheets on what are 
 called immersing rollers. The name is not particularly 
 appropriate, because the actual immersion does not take 
 place until the next operation. This consists in putting the 
 rubber sheets into naphtha contained in zinc-lined wooden 
 boxes fitted with lids. Here, after a time, it assumes the 
 form of an emulsion, technically termed “ dough,” which is 
 
214 
 
 INDIA-RUBBER. 
 
 mixed to a uniform mass on dough rollers if stiff, or if semi¬ 
 liquid in a pug-mill. When working it on the rollers the 
 operative soaps his hands to prevent the adherence to them 
 of the sticky rubber mass. The dough then goes to the 
 spreading machine, which consists of a horizontal roller 
 supported on an iron frame which forms the upper end of a 
 steam chest made of rivetted iron plates. Above the roller 
 along its length is an iron gauge capable of being raised or 
 lowered according to the thickness of the rubber coat 
 required. The dough is placed by the workman by hand or 
 with a spatula on the cloth, which is made to pass between 
 the roller and the gauge, a thin coating of rubber being 
 thereby put on the cloth, the naphtha being evaporated off 
 as the passage over the steam chest is continued. The cloth 
 then passes on to a box roller underneath the machine. The 
 general arrangement of the machine is shown in Fig. 16. 
 
 Even in the comparatively thin coat of rubber which is 
 revealed by the dissection of a macintosh, there may be as many 
 as six individual coatings which go to make up the bulk. It is 
 quite unusual, moreover, for all these coatings to consist of 
 the same rubber. A common procedure is to fill up the 
 pores of the cloth, especially if it be a black one, with a first 
 coating made of pure rubber and lampblack. On this a 
 number of coats of “ body ” are spread, this being of com¬ 
 pounded rubber; a “ surface” coat of still another compo¬ 
 sition being then applied to the whole. Cloth coated with 
 rubber in this way is known as single texture; for double 
 textures two of such cloths are passed through the doubling 
 machine, consisting of a pair of smooth rollers, so that the 
 rubber surfaces unite. In making these double textures the 
 two single textures which are united may be of the same 
 
INDIA-RUBBER PROOFED TEXTURES. 
 
 215 
 
 sort, or one may be merely a lining with a thin coating of 
 rubber spread on it to facilitate adhesion to the thicker coat 
 on the other piece. By this means various textile materials 
 are rendered waterproof, modern practice embracing cottons, 
 wools, unions of cotton and wool called paramattas, and also 
 silks, the present day business in waterproofs having a 
 much wider scope than in the old days when a macintosh 
 
 FIG. 16. —SPREADING MACHINE. 
 
 meant a heavy, black, somewhat evil smelling garment. To 
 proceed, however, with the manufacture: the advantages 
 which the discovery of vulcanization conferred upon the 
 rubber manufacture were early appreciated in the water¬ 
 proofing branch, where the effects of heat and cold upon the 
 goods had led to widespread complaints. Up to 1884 the 
 form of vulcanization mostly adopted was the Parkes cold- 
 cure process, the cloth being passed over a wooden roller 
 revolving in a trough of liquor, which consisted, generally 
 speaking, of one part of chloride of sulphur in forty of carbon 
 bi-sulphide. The evaporation of the chemical vapours was 
 
216 
 
 INDIA-RUBBER. 
 
 completed by passing the cloth over a hollow drum steam 
 heated, the material being then rolled np and sent to the 
 cutting department of the factory, or sold in the rolls to other 
 firms who made it up into garments. This vulcanizing 
 process, which used to be carried out without any hygienic 
 precautions for the benefit of the workpeople, was a very 
 disagreeable one for all connected with it on account of the 
 poisonous vapours given off by the liquor. Nowadays, 
 owing to the powers possessed by the factory inspectors, a 
 considerable amelioration of the workmen’s lot has been 
 effected. Boxing in of the cold- cure machines, and the pro¬ 
 vision of adequate ventilation whereby the vapours are 
 removed from the work-room, represent in general the 
 methods of reform. So far not much has been done in the 
 way of condensing the carbon bi-sulphide fumes, though it 
 is interesting to note that at the works of the Northern 
 Rubber Company, at Retford, the vapours have been j^assed 
 up a coke scrubber containing an absorbent liquid with 
 results which are reported as very satisfactory. 
 
 This vulcanization process not infrequently leads to fires, 
 which, as a rule, are smothered out with wet blankets kept 
 in readiness, without the aid of any outside fire brigade 
 being requisitioned. Carbon bi-sulphide will ignite by con¬ 
 tact with hot metal, but the usual cause of conflagration is 
 an electric spark caused by friction of the cloth, a high 
 barometer and a dry state of the atmosphere being predis¬ 
 posing conditions. 
 
 Twenty-five years ago some little excitement was caused 
 in the trade by the production by a firm of what were 
 somewhat fancifully termed “electric” waterproofs. At this 
 time of day it is not giving away any secret to say that the 
 
INDIA-RUBBER PROOFED TEXTURES. 
 
 217 
 
 “electric” effect was produced by merely sprinkling the 
 surface of a single texture proof with farina powder before 
 being cold cured. 
 
 As chloride of sulphur in contact with moisture tends to 
 decompose with the formation of hydrochloric acid, it is 
 usual in order to destroy any traces of acidity to expose the 
 cured cloth to the vapour of ammonia, an operation involving 
 very little extra expense or trouble. Stoving in a moderate 
 heat is often resorted to in order to dissipate traces of 
 chemical vapours which cause the proofed cloth to smell. 
 This is not, however, very effective, and it is better to use a 
 purified naphtha for dissolving the rubber where compara¬ 
 tively odourless results are aimed at. 
 
 So much for the curing process used almost universally 
 up to 1884. At this date Waddington patented his Dry- 
 Heat vulcanizing stove, which has since been very generally 
 adopted for double textures, the rubber proofing having 
 been found to withstand heat and cold to a much greater 
 degree than was the case with the older process, though 
 this, it must be understood, is by no means extinct, finding 
 still very general use for thin sin^ textures, especially 
 those which have been colour printed and which are too 
 delicate to stand the heat of the stove. Theoretically 
 Waddington’s patent involved no new principle in the treat¬ 
 ment of the rubber. It was merely the adaptation of the 
 well-known sulphur vulcanizing process to proofed cloth. 
 In the cold-cure process there is, of course, no necessity to 
 have any sulphur in the rubber, but in the dry-heat 
 method sulphur has to be incorporated with the rubber, 
 this being spread in the usual way. The roll of proofed 
 cloth is then taken to the stove, which consists essentially 
 
218 
 
 INDIA-RUBBER. 
 
 of a wooden cased-in structure heated by steam coils, and 
 containing a large number of metal rollers about 6 inches 
 diameter over which the cloth passes at a uniform rate of 
 speed. The time taken in the passage of the cloth through 
 the stove varies according to the amount of sulphur present 
 and the temperature, the latter point having to be care¬ 
 fully considered in relation to the particular textile material. 
 To give an instance, a good paramatta will stand 275° F., 
 while a common one, with a preponderance of cotton over 
 wool, must not be exposed to a greater heat than 
 260° I\, about as low a temperature as can be employed 
 for vulcanization. A good excess of sulphur has to be used 
 in dry-heat mixings, because so much is volatilized during 
 the process. This is rather a. weak point, for not only is 
 there the waste of sulphur, hut the vapours tending to 
 crystallize again in the stove at inconvenient spots have to 
 be removed by a fan, and this causing cold air to enter the 
 stove gives rise to inequalities of temperature and an 
 increased steam consumption. 
 
 Vulcanizing in steam is sometimes resorted to in the 
 case of proofed cloth, hut this is employed more for bed 
 and ground sheetings, etc., which contain a heavy proof on 
 white duck, than for cloth intended for waterproof gar¬ 
 ments. Black surface single textures are, however, usually 
 vulcanized in steam wrapped round a drum, and it is pro¬ 
 bably to this satisfactory process that such material owes 
 its lasting powers, though the water polish containing 
 shellac with which it is finished, must also be considered 
 a safeguard against oxidation. With regard to the relative 
 advantages of the cold-cure and dry-heat processes, much 
 might be written, but for the purposes of this volume it 
 
INDIA-RUBBER PROOFED TEXTURES. 219 
 
 will suffice to say that good work can be turned out by 
 both of them, and that where the business is in incapable 
 hands less bad work will be turned out by the dry-heat 
 process than by the other. The latter is by no means as 
 simple in its action as it is expeditious in its applica¬ 
 tion, and a general ignorance of the theoretical principles 
 involved has in the past led to heavy losses from bad work. 
 
 About ten years ago the system of printing designs upon 
 the single texture proofs was introduced, and led to a con¬ 
 siderable demand for the fabrics so treated. The printing 
 is carried out by engraved copper rollers, on the lines long 
 familiar in calico printing, the effect being produced by the 
 impress of various metallic bronzes upon the rubber sur¬ 
 face, which has been made of a blue, red, green, or other 
 ground tint by previous admixture of colouring matters 
 with the rubber. In order that the coloured bronzes should 
 adhere to the rubber the latter used to be faced with some 
 suitable substance, and patents for the use of such bodies 
 have been taken out by different waterproofers. These 
 bodies include aluminium powder, phosphate of lime or 
 bone ash, farina, finely powdered glass, etc. As time pro¬ 
 gressed, however, it was found that this preparation of the 
 surface was not necessary for the success of the process, 
 and at the present time surfacing is mostly dispensed with, 
 the printing being done direct on the rubber. Compared 
 with what was the case five or six years ago colour printed 
 single textures are in very small demand at the present 
 time, feminine fashions having apparently decided against 
 them, much to the chagrin of the waterproofers, who see 
 their expensive plant in comparative idleness. As already 
 mentioned, this class of proofing is always cold cured. 
 
220 
 
 INDIA-RUBBER. 
 
 With regard to the double textures, probably not more 
 than 1 per cent, of the material is nowadays cold cured, 
 and this only because the textile material will not stand 
 the temperature of the dry-heat stove. Of course, before 
 the introduction of the latter process the double textures 
 had to be cold cured. The procedure generally followed 
 was to spread a thin coat of rubber solution on to the 
 lining, and then by means of smooth rollers to double this 
 on to the proofed cloth just after the latter had left the cold- 
 cure machine. Another method is for the freshly-cured 
 surfaces from two machines to be doubled together on 
 central rollers. Although a considerable amount of cold 
 curing has been done with two or three hydrocarbons as 
 substitutes for the bi-sulphide of carbon, and no complaints 
 have apparently been made with regard to the finished 
 goods, yet the proofers seem in all cases to have reverted 
 to the old procedure as being in their opinion the more 
 satisfactory. It may be taken then that the bi-sulphide of 
 carbon substitute has yet to be found in its application to 
 the curing of waterproof cloth as well as for the dipping 
 process mentioned elsewhere. It has been said above that 
 the spreading machine in general use to-day is substantially 
 the same as patented by Hancock. In the original machine, 
 however, the dough roller was of iron, while to-day it is 
 always made of semi-vulcanite, an improvement made in 
 1870. ' Other improvements in points of detail are the 
 differential pulleys by which the speed of the cloth which is 
 being spread can be regulated from 2 to 6 yards per 
 minute, and the inclusion of a roller at the end of the 
 machine which enables the cloth to be passed along the 
 steam chest at an even rate of speed, although the diameter 
 
INDIA-RUBBER PROOFED TEXTURES. 
 
 221 
 
 of the box on which the proofed cloth is rolled up keeps on 
 increasing. Another improvement, patented by W. Coulter, 
 in 1888, is the bull-nosed gauge by which heavy proofings 
 are forced more completely into the cloth than is the case 
 with the ordinary knife edge gauge. In 1883, Coulter also 
 patented the reversible spreading machine in which there 
 was a spreading gauge at each end of the steam chest. 
 
 Two other types of spreading machine now call for 
 notice. The first is the double deck machine patented by 
 Rowley and Walmsley, in 1897, as an improvement on 
 Walmsley’s original patent. In this there are two spread¬ 
 ing gauges and rollers at each end of the machine, the two 
 drying tables being 27 feet long and 10 feet wide. This 
 length of steam chest is found sufficient to expel the 
 naphtha, and to allow of the second coating of rubber being 
 applied at the back end of the machine as soon as the 
 cloth which has received a coating at the front end has 
 passed over the steam chest. A pair of calender rolls 
 also forms part of the machine. It is claimed for these 
 machines, in addition to the great saving in labour, that 
 owing to the rubber being spread from alternate ends a 
 more perfectly waterproof coating is effected. In the 
 second machine, that patented by Frankenstein and Lyst, 
 in 1899, the main feature is the use of a large diameter 
 spreading roller of hard rubber, by means of which three 
 gauges can spread as many coatings of rubber at the same 
 time. This machine, which is now in regular work, appears 
 from all reports to have amply borne out the statement of 
 the patentees as to economy in working expenses, its out¬ 
 put for the same amount of labour being greatly in excess 
 of that of the old-fashioned type of machine. The extra 
 
222 
 
 INDIA-RUBBER. 
 
 cost of this machine is largely due to the greater diameter 
 of the rubber covered roller, and timorous manufacturers 
 looked with increased apprehension at the loss which must 
 ensue in the case of the naphtha taking fire, an occurrence 
 which is by no means unknown in the industry. As, how¬ 
 ever, no such catastrophe has arisen up to date it is evident 
 that such an eventuality is a remote one. 
 
 At the present time the macintosh trade for the million, 
 as it existed ten or fifteen years ago, has been very largely 
 eclipsed by the so-called rainproof cloths, which it must 
 be confessed have solid grounds for their popularity. The 
 average man does not need to stand about in pouring rain, 
 and where an umbrella is also carried, as is very customary, 
 the rainproof material which is porous is altogether a more 
 agreeable thing than the macintosh, which does not admit 
 of ventilation. Certainly numerous attempts have been 
 made in the direction of ventilated macintoshes, but hardly 
 any success at all has been recorded, and it may be taken 
 as a truism that where air can penetrate water can do 
 likewise. There can be little doubt that the decline of the 
 cheap macintoshes was directly due to the absurdly low rate 
 at which, under stress of competition, they were sold. 
 Such goods of cheap cotton, proofed mostly with oil sub¬ 
 stitute and mineral powders, had hut little power of resist¬ 
 ing atmospheric oxidation, and they soon became worthless 
 from a waterproof point of view. Of course the higher 
 priced coats worn by sportsmen and proofed with almost 
 pure rubber, hold to-day much the same position as in 
 past decades, but the market for these is necessarily a 
 restricted one, and the demand will not keep a factory of 
 any size in full work. As regards the future, the outlook 
 
INDIA-RUBBER PROOFED TEXTURES. 
 
 223 
 
 seems to indicate that for the ordinary business man the 
 rainproof cloth will continue to be in favour on account of 
 its hygienic and lasting properties, while the more expensive 
 goods worn in the past by those who do not carry umbrellas 
 will receive an impetus in their manufacture owing to an 
 increased demand from motorists. It ought also to he 
 added that the attention which has lately been given by 
 the manufacturers to the reduction in weight of macintoshes 
 seems destined to bring about a reaction in the favour of 
 these goods, as it is evident that this will go a long way to 
 minimise the hygienic disadvantages which have been a 
 cause of so much disfavour. With regard to the Continent, 
 where the waterproof trade has never attained the propor¬ 
 tions it once did in Great Britain, the French must be 
 given the palm for artistic productions in various textile 
 materials, especially in silks, and the Russians for sombre- 
 looking garments in which the design and heavy build 
 indicate the useful rather than the ornamental. 
 
 Varying somewhat in its composition from the ordinary 
 macintosh, and considerably so in the use to which it is 
 put, is the diving dress. These are in regular demand by 
 the salvage companies, and also form part of the ordinary 
 equipment of a man-of-war. They are made of double 
 texture twill proofed with pure rubber, and are usually dry 
 heat vulcanized. Testimony is paid to the quality of the 
 rubber proofing by the anxiety displayed by rubber scrap 
 merchants to get hold of the discarded ones. The neck 
 arrangements and gauntlets of these diving dresses are 
 made of vulcanized rubber sheet, and in some cases the 
 makers have large tanks of water in which the goods are 
 put to practical tests before being sold. 
 
224 
 
 INDIA-RUBBER. 
 
 The making up of waterproofed cloth gives employment 
 to a large number of hands, the bulk of them girls who 
 serve an apprenticeship to the trade. A common complaint, 
 which no doubt is by no means peculiar to the waterproof 
 trade, is that as soon as a girl gets efficient she leaves to 
 undertake the responsibilities of matrimony. The jointing 
 of seams is effected either by pasting on a strip of cloth 
 with rubber solution or by sewing, the latter being now 
 often done by sewing machines run by electric motors. 
 Although all the rubber works which have taken up the 
 proofing branch have their own cutting out and making-up 
 rooms, a good deal of the proofed cloth is sold in the roll to 
 others who do the tailoring only. Since the introduction of 
 the dry-heat vulcanization, rubber proofings in the roll 
 have been exported for making up at their destination. A 
 good deal has gone of late years to Madrid, a very trying 
 climate for such material owing to the extremes of heat 
 and cold which are experienced. Canada again has been a 
 large customer, but owing to the rubber companies of the 
 Dominion taking up the proofing branch, the British 
 imports have suffered a great decline in recent years. 
 
 For this export business it is desirable that only really 
 good material should be made, as any defects give rise to so 
 much more trouble and expense than in the case of the 
 home trade. “ Our dry-heat vulcanized proofings are 
 guaranteed to stand all climates ” is a common form of 
 advertisement. Where the temperatures do not run into 
 extremes, and where there really is plenty of vulcanized 
 rubber present, this form of notice is no doubt quite in 
 order. But it is inapplicable to a proofing consisting in 
 the main part of oxidized oils and mineral matters. Cases 
 
INDIA-RUBBER PROOFED TEXTURES. 
 
 225 
 
 have come under the author’s notice where defective 
 proofing has been returned to England from abroad, and 
 investigation has shown that the poor quality of the rubber 
 mixing has resulted in its own undoing. There was nothing 
 which could be specifically urged against the manufacturer 
 as a defect in workmanship, except that the rubber which 
 was said to have undergone the dry-heat process to fit it 
 for its duties was there in such very small amount. 
 
 I.R. 
 
 Q 
 
CHAPTER XVII. 
 
 INDIA-RUBBER TYRES. 
 
 The amount of matter which has a legitimate claim for 
 consideration in this chapter is so large that the selection 
 which is imperative is by no means an easy task. An 
 attempt, however, will he made to summarise the more 
 important points relative to the manufacture of rubber 
 tyres, a topic which appears to be very imperfectly under¬ 
 stood by the great army of cyclists and motorists who buy 
 and use them. As a prelude to the main subject, a word 
 may not be amiss with regard to orthography. It may or 
 may not be a matter of universal knowledge that the 
 Americans always write “tire’ where we write “tyre, 
 and there is a widespread disposition in this country to 
 denounce this as a flagrant instance of the Americanising 
 of pure English. As a matter of fact, in this particular 
 case, it is we English who are in the wrong, as our form of 
 spelling the word has no justification at all. It is not to 
 be found in any standard dictionary, 1 and indeed is of quite 
 recent growth, having come in with the rise of the rubber 
 tyre into popular favour. Without going further back into 
 the classics, it will suffice as regards etymology to say that 
 
 1 Certainly we have, “On her head she woi-e a tyre of gold” 
 (Spenser’s “Faerie Queene”), but then Spenser was notorious for 
 invention in spelling, and cannot he taken as an authority. 
 
INDIA-RUBBER TYRES. 
 
 227 
 
 “ tire ” is derived from the word “ to tie,” and means some¬ 
 thing which “ ties ” the rim of the wheel. Perhaps a more 
 correct spelling would be “ tier,” but for the sake of euphony, 
 no doubt, the contraction into one syllable was adopted 
 from the first. It will be seen, then, that the Americans, 
 instead of being to blame, are actually putting us right in what 
 is one of the stock mis-spellings of the day. It would require 
 some research to find out who was the culprit in modern 
 times primarily responsible for the current English spell¬ 
 ing, but not to be too severe on him, in the absence of 
 his defence, it is possible that the main object was to avoid 
 confusion with other words spelt the same way, but of 
 totally distinct derivation and signification. Having said 
 so much by way of protest and in self-defence, the author 
 will continue to spell according to the English custom to 
 save the typesetter the trouble of correcting him. Rubber 
 tyres are not troubled with a history, and authors have 
 therefore no need to rummage among dusty archives for 
 their material. Solid rubber tyres, as applied to perambu¬ 
 lators, were in use some time ago, but the early suggestion 
 of pneumatics by R. T. Thomson, who took out a patent 
 in 1847, met with no success, and it was not until 1889, 
 when Dr. Dunlop, of Dublin, took out his patent, that 
 the inauguration of an immense business took place. To 
 give a brief account of the manufacture of the different 
 classes of tyres, the perambulator tyre may be dismissed 
 with the observation that it is usually made of a low quality 
 compounded rubber passed through the tubing machine and 
 vulcanized in iron moulds in the press. Solid cab tyres are 
 also made in the forcing machine with a die which moulds 
 them to the required form for attachment to the wheel. 
 
 Q 2 
 
228 
 
 INDIA-RUBBER. 
 
 Fig. 17 shows a modern type of forcing machine for making 
 solid tyres. They are generally vulcanized embedded in 
 talc in open steam, a cover being put over them to protect 
 
 FIG. 17.—CAB TYRE FORCING MACHINE. 
 
 them from drops of condensed steam. Close attention to 
 detail in the apparently simple operations involved are 
 necessary to prevent porosity, or “blowing,” a good deal of 
 trouble being sometimes caused by this phenomenon, which 
 seems to result more often from lack of official supervision 
 
INDIA-RUBBER TYBES. 
 
 229 
 
 in the details of working than from any malevolent con¬ 
 stituent of the rubber or chemicals used. Up to compara¬ 
 tively recent times the use of the solid tyre was confined 
 to cabs, carriages and light motor vehicles. With the 
 arrival, however, of the motor omnibus and merchandise 
 vehicles, tyres of much larger dimensions of both single 
 and twin type have come into existence, and this branch of 
 the business, which at present is in a state of constant 
 evolution, must assuredly in the future make a large and 
 increasing claim upon the supply of raw rubber. As far as 
 the principles of the manufacture are involved, these large 
 tyres do not call for special mention, except in the use of 
 moulds for vulcanizing, these being usually dispensed with 
 in the case of the cab tyre. 
 
 In the ordinary solid tyre the rubber is all in one piece, 
 but in the recently brought out Hartridge tyre it is made 
 up of a large number of separate segments, somewhere 
 about a hundred, each of which it is claimed acts indepen¬ 
 dently, as well as collectively, for producing resiliency and 
 an effective grip of the road’s surface. A point about this 
 tyre which should minister to economy is that a worn 
 segment can be replaced by a new one at a trifling cost 
 compared with what is incurred in the case of tyres in one 
 piece. The colour of solid tyres, though usually grey, 
 may be varied according to the ideas of the patentees or 
 manufacturers, and will depend, of course, upon the par¬ 
 ticular colouring matters mixed with the rubber, which for 
 solid tyres is always more or less compounded. 
 
 Coming now to the pneumatic cycle tyre, this, whatever 
 the mode of attachment to the wheel may be, consists 
 usually of an inner air tube of pure vulcanized rubber and 
 
230 
 
 INDIA-RUBBER. 
 
 an outer cover of canvas and rubber. The mode of manu¬ 
 facture is as follows. The rubber is dry-mixed with sulphur 
 upon the rollers and then calendered upon a faced sheet of 
 cloth to the required thickness. It is then stripped and cut 
 into bands for inner tubes and covers respectively. For 
 inner tubes the strips are rolled over a mandril, the joint 
 being made with solution and “rolling.” A narrow strip 
 of pure rubber tape is then placed longitudinally over the 
 joint, the tube while still on the mandril being vulcanized 
 in steam. After the vulcanization the joint becomes part 
 and parcel of the tube, and effectively prevents any giving 
 way under pressure. For considerations of appearance the 
 tubes are turned inside out after vulcanization, so that the 
 joint is on the inside. A good many inner tubes are also 
 made in the seamless form by means of the tubing machine. 
 In making the outer covers a strip of calendered rubber has 
 another strip solutioned to its centre so as to give the extra 
 thickness required for the tread and the desired design. 
 This strip is then joined up to form an endless band and 
 placed on a metal drum, the surface of which is engraved 
 with the design for the non-slipping surface and then 
 vulcanized. After this it is solutioned on to an insertion 
 of linen or cotton duck, fitted with endless wires or beaded 
 edges according to the type of tyre required, a complete 
 outer cover thus being formed. This method was that 
 commonly in use to produce what is popularly known as a 
 hand-made cover, but it should be mentioned that this 
 form of cover is now almost obsolete. The tyre cover 
 almost universally in use at the present time is what is 
 known as the vulcanized cover. The mode of manufacture 
 is very similar to that just described, the main difference 
 
INDIA-BUBBEB TYBES. 
 
 231 
 
 being that the rubber is applied to the linen or canvas 
 casing in the un-vulcanized condition, and the whole casing 
 is fitted, with the rubber downwards, to the engraved metal 
 drum and vulcanized. It may be mentioned with regard 
 to the rubber strip that some manufacturers, instead of 
 building this up from two or more pieces, obtain the neces¬ 
 sary section by calendering a strip through bowls which 
 have been hollowed out. The strip on issuing from the 
 calender is carried on an endless band and cut to the 
 desired lengths. The method of vulcanization in use at the 
 Dunlop works has already been mentioned in Chapter IV. 
 
 During the life of the Dunlop patents considerable profits 
 were made in this manufacture, their actual amount 
 fluctuating with the price of the raw rubber. Now that the 
 monopoly has run its course these profits have vanished to 
 a great extent, and the business has little attraction except 
 for those who can manufacture on a very large scale. As 
 the firms engaged have their reputations to conserve, they 
 all produce tyres made of the best material obtainable, and 
 where second or third qualities are made to fit the needs of 
 those of slender resources, they are sold strictly as such 
 and on their merits. A useful plan adopted by the North 
 British Rubber Company was to make the lower qualities a 
 different colour from the best, so that a purchaser from a 
 middleman could have no doubt as to what he was getting. 
 Whether the use of the best Para rubber is absolutely 
 necessary, or whether a blend containing a certain propor¬ 
 tion of a lower quality gives equally good results in practice, 
 is a matter that the several manufacturers have had under 
 close consideration ; with such details the purchaser has no 
 concern. It has become customary for makers to give 
 
232 
 
 INDIA-RUBBER. 
 
 guarantees of lasting power with their tyres, and under the 
 existing conditions of competition no firm will sell as best 
 quality anything that is likely to show up badly in practice. 
 Though the quality of the rubber is important, yet the 
 correctness or otherwise of the vulcanization has a great 
 deal to do with the longevity of the tyre. Whatever may 
 have occurred in dark places, it has certainly not been 
 customary to use reclaimed rubber in pneumatic tyres, 
 though, in order that merit should be awarded where it is 
 deserved, the author has cognisance of a pneumatic tyre 
 made entirely of reclaimed rubber which was stated (from 
 an interested source) to be eminently satisfactory. It has 
 been sought to prevent sun-cracking or surface oxidization 
 of tyres by admixing certain compounds containing paraffin 
 wax with the rubber. This admixture only seems to have 
 had a partial success, and it must not be overlooked that 
 with every per cent, of such non-elastic matter added the 
 proportion of rubber is reduced by the same amount. The 
 principle underlying the use of such preservatives is, pre¬ 
 sumably, the closing up of the pores of the rubber from the 
 insidious attacks of atmospheric oxygen, and on a 'priori 
 grounds it should meet with success. In practice, however, 
 other considerations are involved, and it may easily happen 
 that the expected advantages are nullified. 
 
 When a comparison is made between the cost of different 
 makes of pneumatic tyres, their relative weight must not 
 be overlooked. The tendency of the present day is to use 
 light tyres, which allow of greater speed being attained 
 without more effort, and a pair of such tyres will naturally 
 contain less rubber than those of more solid build. Of 
 course, the lighter the tyre the greater the liability to 
 
INDIA-RUBBER TYRES. 
 
 233 
 
 puncture, especially where the canvas is exposed, except 
 just on the tread. It would seem that the increased use of 
 chert—a massive form of flint—on British roads is causing 
 a good deal of trouble to cyclists. As chert is only being 
 used in certain districts where it can be produced locally, it 
 would not be a bad idea for the cycling handbooks to com¬ 
 pile some information as to the districts in which it is 
 advisable to ride with caution. Although motor tyres will 
 pick up chert fragments from the roads until their surface 
 is studded with them, no very serious damage results, but in 
 the case of the light cycle tyre the effect is often catastrophic. 
 
 Turning now to the motor tyre, which has made such 
 immense strides in recent years, there is but little to say 
 with regard to the manufacture of the rubber which has not 
 been said already. No attempt will be made to enumerate 
 the various types of motor tyres, both pneumatic and solid, 
 which have been brought out for use on different kinds of 
 vehicles. Evolution is proceeding at a more rapid rate in 
 this branch of the rubber manufacture than perhaps in any 
 other, and any exhaustive commentary would speedily 
 require re-writing. In one direction, however, we seem 
 likely to remain stationary, and that is with regard to the 
 replacement of rubber by some other substance. No pro¬ 
 gress has to be reported with the various suggested applica¬ 
 tions of leather, and it does not seem that rubber has 
 anything to fear from any of the substitutes proposed for 
 it. For a satisfactory pneumatic tyre it is necessary to pay 
 as much attention to the fabric as to the quality of the 
 rubber, a point early recognised by the well-known firm of 
 Michelin et Cie., of Clermont-Ferrand. This firm made a 
 special study of the canvas used in their tyres, and now 
 
234 
 
 INDIA-RUBBER 
 
 weave their own from Sea Island cotton spun at Bolton in 
 Lancashire. Apropos of the position attained by the firms 
 of Michelin and the Continental Rubber Company, of 
 Hanover, in the motor tyre trade compared with the British 
 producers, it must be remembered that the former took up 
 the business at an earlier date. The British firms showed 
 a good deal of hesitancy in committing themselves to the 
 large capital expenditure necessary for moulds, though 
 when the use of the motor-car became as general in Great 
 Britain as it was in France, British firms, notably the 
 Dunlop Company, set to work at once to compete with the 
 foreign makers of tyres. The latter had, however, already 
 got a firm foothold, and in spite of the progress made by 
 several home firms, they have more than sustained their 
 position as regards the pneumatic tyre. With the solid 
 tyre, especially those designed for omnibuses, lorries, etc., 
 and made in the twin type, the position of British firms in 
 the front rank is unchallenged. Of course, Continental 
 competition has to be met, and German tyres are by no 
 means unknown on London motor ’buses, but the situation 
 as a whole is much more favourable to the British rubber 
 manufacturer than in the case of the pneumatic tyre. 
 Mineral matter enters largely into their composition, 
 strength being of more importance than elasticity. 
 
 In the pneumatic tyres, also, although the best rubber is 
 called for, there is no necessity to make the tyre entirely of 
 rubber and sulphur, the addition of a small amount of 
 zinc oxide, magnesia, or other chemical giving increased 
 toughness, and tending, moreover, to decrease the liability 
 to sun-cracking. The rubber which forms the tread is, it 
 may be mentioned, somewhat heavily compounded. 
 
INDIA-RUBBER TYRES. 
 
 235 
 
 Although tubeless tyres have been largely made and sold, 
 especially in America, the pneumatic motor tyre as a rule 
 has an inner tube, which is manufactured on the same lines 
 as described for cycle tyre tubes. In making up the cover, 
 when intended for vulcanizing in a mould, the strips of 
 canvas spread with rubber solution are built up with strips 
 
 FIG. 18.— SECTION THROUGH IRON MOULD SHOWING PNEUMATIC 
 MOTOR TYRE DURING VULCANIZATION. 
 
 of calendered rubber mixed with sulphur on a circular 
 mandril by hand. When the tyre has been built up the 
 mandril, or core, as it is also called, is put into the 
 iron mould, clamped down, and put in the hydraulic vulcan 
 press. The core, it should be said, is made in four segments 
 in order to facilitate its removal from the tyre after vul¬ 
 canization. Fig. 18 represents a section of such a tyre 
 mould. 
 
236 
 
 INDIA-RUBBER. 
 
 In the case of the solutioned tyre the rubber strips are 
 already vulcanized before being made up ; this form of 
 tyre, though not considered so satisfactory as the other, 
 obviates the provision of expensive moulds, and further, it 
 has the advantage that the canvas has not had to undergo 
 the vulcanizing heat. 
 
 Special types of tyres, of course, call for a variation in 
 the procedure just mentioned. In the Palmer cord tyre, 
 for instance, made by the Silver town Company, the woven 
 canvas is replaced by approximately straight threads or 
 cords, each of which has a rubber coating. In this tyre it 
 has been sought to prevent the constant friction between 
 the warp and the weft which takes place with canvas as 
 ordinarily woven. 
 
 In the Collier tyre, which is now made with beaded 
 edge or mechanical fastening, special attention has been 
 paid to reducing internal friction between the canvas and 
 rubber. The necessity of getting these components as 
 far as possible into a perfectly homogeneous mass has not 
 always been sufficiently recognised, though it is difficult to 
 over-rate its importance. Where there is not a very close 
 adhesion between the fabric and the rubber, internal friction 
 and consequent heating will result when the tyre is in con¬ 
 tinuous use, and it will soon become defective. It is 
 probably not an exaggeration to say that 50 per cent, of 
 the wear and tear of a tyre lies in the details of its con¬ 
 struction, quite apart from the intrinsic quality of the 
 rubber, and it is quite possible for a tyre produced at a 
 certain cost per pound to prove less efficient and lasting 
 than one in which the first cost of the materials was only 
 half as much. Granting the truth of what has just been 
 
INDIA-RUBBER TYRES. 
 
 237 
 
 laid down, it will be recognised that chemical analysis is of 
 very little use in enabling us to judge of the value of a tyre 
 as distinct from the monetary value of its component parts, 
 and more reliable information is likely to be yielded by 
 physical tests referred to briefly in another chapter. Of 
 course analysis has its utility in strictly manufacturing 
 circles, it is only from the tyre-user’s point of view that its 
 indications are apt to prove illusory. 
 
 The matter of repairs to old or damaged tyres is one of 
 considerable and growing importance. It is often a moot 
 point whether it is worth while to doctor up an old tyre, or 
 whether the purchase of a new one is not the soundest 
 policy. Where money is no object the latter course is to be 
 recommended, both in the interests of the motorists and the 
 trade ; but as there is a large and increasing number of 
 owners whose purses are by no means unlimited, it may be 
 taken that the businesses of the tyre repairers, as also of the 
 repair machinery outfitters, such as Harvey Frost and Com¬ 
 pany, will continue to flourish. By means of the vulcanizing 
 arrangements introduced by the firm just mentioned, 
 patches of rubber can be neatly and expeditiously vulcanized 
 on to tubes or covers by those who do not confess to 
 any technical knowledge of the rubber trade. Although 
 complete unanimity does not prevail on the point, there is 
 a general consensus of opinion in favour of the vulcanized 
 patch as against that which has been solutioned on. The 
 latter, especially in the case of new treads, frequently fails 
 to be proof against the intrusion of road metal, and allows 
 moisture to enter to the detriment of the canvas. On the 
 other hand, where the tread is vulcanized on, it will be 
 seen that at the point of attachment the rubber has 
 
238 
 
 INDIA-RUBBER. 
 
 undergone a double vulcanization, which can by no means 
 be considered conducive to its longevity. 
 
 With regard to the ultimate destination of worn-out 
 motor tyres something will be seen in the chapter on 
 recovered rubber. In some cases, however, the old tyres 
 are doctored up with new treads, and sold again as second 
 quality goods. Where no attempt is made to pass them off 
 as first quality, and where the original maker’s name has 
 been removed, there does not seem much to urge against 
 this practice. That it has not, however, commended itself 
 to the motoring authorities is seen in the advice given to 
 motorists, and emanating, it is understood, from high 
 quarters, to slit up the tyres before selling them for scrap 
 rubber. 
 
CHAPTER XVIII. 
 
 INDIA-RUBBER BOOTS AND SHOES. 
 
 The manufacture of what are so generally known under 
 the name of goloshes appears to have been originated by 
 Thomas Hancock as early as 1825. These were made of 
 pure cut sheet, the sole, sometimes of rubber and sometimes 
 of leather, being fastened to the “uppers” by solution; 
 they were finished off with a lining of cloth or leather. At 
 the present time the manufacture of rubber footwear, to use 
 the American expression, is carried out on very different 
 lines in the numerous large factories which, especially in 
 America, are devoted entirely to this business. The demand 
 in Great Britain, although showing an increase in recent 
 years, has never been a large one, and there are only three 
 or four home firms who are engaged in this branch. Of 
 these, by far the largest producer is the North British 
 Rubber Company of Edinburgh, in the foundation of which 
 American capital and energy were prominent. An increasing 
 export trade is done with China and other countries where 
 the golosh is largely worn. In Russia there is a large 
 demand, more especially for the higher-priced snow boots, 
 with or without fur tops, and other artistic developments 
 unknown in Great Britain. The Russian and Siberian 
 business is chiefly done by the two large home firms already 
 mentioned as located at St. Petersburg and Riga, the high 
 tariff being a bar to the German producers. In South- 
 
240 
 
 INDIA-RUBBER. 
 
 Eastern Europe and the Adriatic littoral the author’s own 
 experience, backed by Consular reports, points to an 
 increasing market in which American invasion is being 
 strongly contested by the Russian houses, racial affinity 
 and the common basis of the Slav tongues being points of 
 vantage for the latter. The Scandinavians are the latest 
 comers into the manufacturing field, the Norske Galoge 
 Fabrik Aktieselskab at Mjondalen-Drammen in Norway, 
 and the Gummi Fabrik Aktiebolag at Helsingborg in 
 Sweden, both being considerable producers. The latter 
 stated its output two years ago at 5,000 pairs per day, 
 roughly, 1,500,000 pairs per annum, a sufficiently formidable 
 figure, although it is easily distanced by the 8,500,000 
 pairs per annum by the Riga-Prowodnik Company in Russia. 
 With regard to the output of the large American concerns, 
 it may be mentioned that the factory of the Boston Rubber 
 Shoe Company has a daily capacity of 55,000 pairs. 
 
 In France, the Etablissement Hutchinson, a factory 
 founded at Langlbe fifty years ago by an American, has 
 an output of 2,500,000 pairs per annum. 
 
 The manufacture, though on the face of it comparatively 
 simple, necessitates close attention to detail if satisfactory 
 results are to be assured. Each factory has its special 
 formulae for the rubber compound and varnish, and it is 
 especially in regard to the latter that some firms have a 
 pre-eminence in the trade. While the uppers are always 
 made of new rubber, a commoner mixing containing 
 reclaimed rubber is generally used for the soles. In making 
 goloshes the compound rubber is calendered on the fabric to 
 the required thickness and cut into the necessary shape by a 
 knife. For the soles, special small embossing calenders are 
 
INDIA-RUBBER BOOTS AND SHOES. 241 
 
 used, whereby the pyramid or other design is put on. In 
 a recent improvement the sole is both embossed and cut 
 out of the sheet at the same time. The making-up is 
 usually performed by hand on an iron mould, the necessary 
 rubber and fabric parts for each pair being put into a 
 separate box and handed to the workman. Quite recently 
 the making-up has been done in some American factories 
 by the machine patented by Doughty, though how far this 
 is destined to replace hand labour generally is a matter 
 which is yet in the region of speculation. The golosh 
 having been finished on the mould, a coating of black 
 varnish is applied, usually by hand, though a machine has 
 recently been introduced for the purpose in America, by 
 which it is said that the varnish is more evenly applied. 
 Boiled linseed oil is the most important constituent of this 
 varnish, and it is very essential that the lamp black should 
 be quite free from greasy and resinous matters. The shoes, 
 while still on the moulds, are run in large numbers at once 
 on trucks into a dry-heat vulcanizing stove, the temperature 
 and time being carefully regulated according to the 
 composition of the rubber. 
 
 A common defect of goloshes has been their liability to 
 come off at inopportune times, and it is of interest to note 
 the improvement introduced by the Biga-Prowodnik Com¬ 
 pany to remedy this. A stiff back or stay is inserted in the 
 heel, and this, in conjunction with a stud placed on the 
 outer side, has also the advantage of allowing the shoe to be 
 removed without the wearer having to bend down and use 
 the hands. This is a matter of some importance in Bussia, 
 where the golosh is so universally worn, and is continually 
 being put on and off. 
 
 I.R. 
 
 R 
 
242 
 
 INDIA-RUBBER 
 
 The golosh, of course, is by no means the only article 
 turned out by the rubber shoe factories. Snow boots, thigh 
 boots, Plimsolls, Wellingtons, and so on, contribute to 
 the output, though all the varieties may not be made at 
 one and the same factory. With regard to Wellington 
 boots, the specification for the Royal Gunpowder Factory 
 limits the mineral matters to sulphur and oxide of zinc. If 
 this requirement is really insisted on, it means a decided altera¬ 
 tion in the usual mixing, in which litharge is always found. 
 
 In 1902, A. 0. Bourne, of the United States, patented a 
 process for vulcanizing rubber shoes in a jacketted pan 
 under pressure, and instead of using compressed air he put 
 in the pan a solid chemical substance which gasified under 
 heat, thus providing the necessary pressure. It is said that 
 by this process a great saving in the time of vulcanization 
 is effected, and also that the value of the goods is enhanced. 
 
 Perhaps the most vulnerable part of the golosh is the 
 heel, and a glance at patent literature shows that this 
 matter has been by no means neglected. A few years ago 
 the Boston Rubber Shoe Company of U.S.A. brought out 
 the “ service heel,” which was made with a rolled edge and 
 brought up on the rear as a further protection. 
 
 C. M. Berry, of U.S.A., proposed to fit the outside of the 
 heel with hard rubber, so as to give greater durability. It 
 was urged as an additional advantage that, as the heel was 
 not noiseless, the wearer need not feel so much of a sneak. 
 This point, by the way, has always militated against the 
 increased use of the golosh in England, and if the vulcanite 
 heels prove satisfactory one might expect an increase of 
 business among those who have no desire to emulate the 
 silent step of the policeman on his midnight beat. 
 
CHAPTER XIX. 
 
 RUBBER FOR INSULATED WIRES. 
 
 In proportion to other insulating media vulcanized rubber 
 does not hold to-day the position it once did. This is not 
 attributable so much to the trouble caused by the defection 
 of cables insulated with a poor quality of rubber as to the 
 comparative economy attending the use of fibrous bodies 
 soaked in rosin oil or vulcanized bitumen. For very high 
 pressures, and for connections where flexibility is of import¬ 
 ance, the vulcanized rubber cable still holds the first place, 
 and is made to-day under more skilled supervision as 
 regards the quality and treatment of the rubber than was 
 at all general ten years ago. Most of the large cable 
 manufacturers have now got rubber machinery of their 
 own, though formerly it was more common for them to buy 
 the rubber, both pure and compound, from the rubber manu¬ 
 facturers. This still obtains in several cases, contracts being 
 placed for material to be composed according to formulae 
 given. The compounded rubber is sent to the cable works 
 interrolled with cloth, the necessary vulcanization being 
 effected on the finished cable. Three principal classes of 
 rubber are utilised in cable making. First, the fine sheet, 
 used as a first coating for the wire, this being either cut 
 sheet or spread sheet. The latter is now generally used and 
 is made from the best hard-cure Para rubber which has 
 been aged for some months. If used directly after 
 
 r 2 
 
244 
 
 INDIA-RUBBER. 
 
 washing and drying it has not quite the same strength. 
 Secondly,there are the compound rubbers, concocted accord¬ 
 ing to instructions received. These may be divided into 
 two classes, one known as a separator, having little or no 
 free sulphur, and the other containing the full amount 
 of sulphur necessary for efficient vulcanization. Thiidly, 
 there is the rubber-faced tape used for covering the cable. 
 The less said about the rubber in this the better, it being 
 as a rule composed of a poor class of rubber compound. 
 It consists of cotton cloth having a coating of lubbei put 
 on both sides by the spreading machine. With regard to 
 contracting for these materials, it is one thing to stipulate 
 what is to be supplied, and another thing to see that you 
 get it. Certainly rubber analysis has made such progress 
 of late years that there is no particular difficulty m deter¬ 
 mining whether the pure rubber strip and the rubber-faced 
 tape are up to requirements. The difficulty comes in with 
 regard to the second quality rubber used for the compounds. 
 Some cable makers specify a particular brand, say Camata 
 or Columbian, but analysis is quite incapable of saying 
 whether a particular brand has been used alone or in con¬ 
 junction with another brand of somewhat similar nature. 
 A great deal is made in some quarters of the resin figures 
 for each rubber, but there are many cases where they form 
 a broken reed to depend upon. In the present state of our 
 knowledge there would remain plenty of room for hard 
 swearing on both sides if a dispute as to the particular 
 rubber used came under judicial cognisance. In a recent 
 paper, Atkinson and Beaver 1 point out that the rate of 
 oxidaiion of pure spread rubber strip of different makes 
 1 “ Trans. Inst, of Efectricaf Engineers,” 1905. 
 
RUBBER FOR INSULATED WIRES. 
 
 245 
 
 varies a good deal, and it would be interesting to know if 
 uniformity in this respect occurs regularly in strip of the 
 same make. Besides cut and spread pure rubber strip, 
 rolled strip is also used for electrical purposes, especially 
 when transverse rigidity is required. In some cases in 
 order to impart apparent toughness to the strip, it is slightly 
 vulcanized with chloride of sulphur, an operation that 
 requires to be carefully carried out. The presence of a 
 small quantity of sulphur in the strip indicates the employ¬ 
 ment of this process, always supposing that the rubber is 
 pure and does not contain any substitute. Other ways of 
 surface hardening the freshly cut rubber strip or narrow 
 ribbon are in use by individual manufacturers, but of these 
 it is not proposed to say anything in detail. The same 
 degree of reticence will be observed in regard to the finish 
 which strip receives in order to destroy its adhesiveness, 
 the processes employed by the several manufacturers show¬ 
 ing considerable variation. Owing to the injurious effect of 
 copper upon rubber, a fact referred to earlier in this volume, 
 it is the regular custom to give the copper wires a coating 
 of tin. This tinning may be well or inefficiently carried 
 out, but even when done in a first-class manner, without 
 economising in tin, it is a common thing for copper sulphide 
 to be found adhering to the first coating of pure rubber in 
 an old cable or in one which has broken down owing to too 
 great an electric pressure. The explanation of this probably 
 lies in the supposition that the tinning process does not 
 result in merely putting a layer of pure tin upon the copper, 
 but that a tin-copper alloy is formed which under certain 
 conditions attacks the sulphur in the partially vulcanized 
 rubber. 
 
246 
 
 INDIA-RUBBER. 
 
 The complaints of cable makers of the front rank regard¬ 
 ing the unfair competition they have to meet owing to the 
 facility with which the rubber insulation can be sophisticated 
 are doubtless perfectly justified. Possibly those who use 
 second-class material may put forward pleas of justification 
 which call for consideration, but whether or no, it is mani¬ 
 festly unfair for the municipal magnates who have the 
 giving of cable contracts in their power to ask for first 
 quality material, and then to give the contract on account of 
 price to a firm whose insulation is by no means first-class. 
 As a means of combating the effects due to this lack of 
 discrimination, an Association of cable makers was formed 
 a few years ago, and buyers of cables bearing a certain mark 
 now know that they are getting the best quality. This step 
 was certainly justified, both in the interests of the buyers 
 and of the manufacturers of reliable insulation. If inferior 
 cables are now bought as first-class, it must be attributed to 
 caprice, indifference or parsimony on the part of the pur¬ 
 chasers, who will no longer have any justification for heaping 
 anathemas upon rubber insulation generally. Owing to the 
 porosity of vulcanized rubber under pressure—in which 
 respect it differs greatly from gutta-percha—it is unsuitable 
 for submarine cables. At least this is the opinion generally, 
 though not universally, held by cable makers. Messrs. 
 Hooper and Company, of London, have long held a contrary 
 opinion, and have supplied rubber-insulated cables for many 
 years past for submarine purposes. These cables appear 
 to have given every satisfaction, though it should be noticed 
 that they have been mainly laid in estuaries and shallow 
 waters and not at great ocean depths. In America the 
 virtues of india-rubber for deep-sea work have been loudly 
 
RUBBER FOR INSULATED WIRES. 
 
 247 
 
 sung in recent years, and a considerable mileage has been 
 laid. The rubber in this case is not lapped on by machinery, 
 as in electric light and power cables, but is applied in a 
 seamless state by a sort of tubing machine. The firm to 
 whom credit is due for firmly establishing the capabilities 
 of rubber in this connection is the Safety Insulated Wire 
 and Cable Company (New York), whose successful use of 
 seamless rubber insulation in the cable system connecting- 
 up the Philippine Islands led to them obtaining the contract 
 for the Washington-Alaska cable, an enterprise of con¬ 
 siderable difficulty owing to climatic conditions. This cable 
 consists of a conductor of nine copper strands, having first 
 a seamless covering of pure Para rubber, and secondly a 
 layer of vulcanized rubber also applied in the seamless 
 manner. Jute covering and steel armouring complete the 
 cable, which is altogether 2,088 miles in length. With regard 
 to transit, such cable has a great advantage over gutta¬ 
 percha, as water tanks are not required. There are now 
 about 5,000 miles of rubber-insulated cable laid by 
 Americans, both in torrid and ice-cold waters, and at 
 depths down to nearly two miles, so that its capabilities 
 can be watched under varied and exacting conditions. 
 Sceptics may say that two or three years is insufficient 
 time in which to give a definite opinion, but at any rate 
 it certainly seems that the threatened extinction of the 
 gutta-percha supply may be viewed without deep concern as 
 far as its principal application comes up for consideration. 
 
 A comparatively new use for rubber-insulated wires is in 
 collieries and metal mines. Although the electric drill has 
 not made much progress, electric hauling in the levels and 
 on inclined planes is well established, a notable instance 
 
248 
 
 INDIA-RUBBER. 
 
 being seen in the installation put down by a Christiania 
 firm in the Roros copper mines in Norway. Electric wind¬ 
 ing in deep colliery shafts is in operation in Germany, and 
 is now being introduced into South Wales, while electric 
 pumping is taking the place of steam power to some extent 
 in mining districts. For these purposes, where dampness 
 is always to be apprehended, the rubber cable has good 
 prospects, though present practice is by no means confined 
 to this type. 
 
 A class of. cable which was shown for the first time at 
 the last Paris Exhibition under a working pressure of 
 25,000 volts is due to Signor Emmanuel Jona, of Pirelli and 
 Company, Milan. This has a complete insulation of several 
 layers of rubber, over which layers of prepared paper or 
 jute are wound, this giving a more equable stress through 
 the insulation. 
 
 The electrical properties of rubber insulation have been 
 referred to in an earlier chapter, though as fibrous insula¬ 
 tion was not included in the figures quoted it may be 
 mentioned here that the specific inductive capacity of the 
 diatrine paper insulation of Messrs. Glover and Company 
 has a value of 2*8, much the same as good class rubber insula¬ 
 tion. Altogether the progress that has been made in late 
 years in substituting rubber by impregnated paper and 
 bitumen hardly points to any prospective increased demand 
 for the former in this particular application. 
 
CHAPTER XX. 
 
 VULCANITE. 
 
 The discovery and manufacture of vulcanite, or ebonite, is 
 almost as old as that of vulcanization itself, its initiation 
 being due to Goodyear. The manufacture does not differ 
 essentially from that of soft rubber goods, except that the 
 amount of sulphur used is considerably larger—from 30 up 
 to as much as 60 per cent, in some cases. The product is 
 well known in the form of combs, knife handles, photo¬ 
 graphic dishes, match boxes, etc., while it finds a 
 large application in the electrical industry and in chemical 
 manufacturers’ plant. As regards the extent of the manu¬ 
 facture in Great Britain, but little of a complimentary 
 nature can be said, for both in respect of quality of goods 
 and the output Continental countries, more especially 
 Germany and France, have long got ahead of us, and still 
 maintain their position. Not that the manufacture is non¬ 
 existent or even moribund in this country; several of our 
 larger rubber factories make the material, and one concern, 
 the Scottish Vulcanite Company, of Edinburgh, is concerned 
 entirely with it; but still, compared with our pre-eminence 
 in most of the other branches of the industry, we hold a 
 poor position with regard to vulcanite. This statement 
 may conceivably be challenged, but it gains considerable 
 
250 
 
 INDIA-RUBBER. 
 
 support in the returns, showing the purchases made abroad 
 by our Government Departments. The Post Office alone 
 bought over two thousand pounds worth of vulcanite on the 
 Continent in 1905, and if returns could be obtained from the 
 electrical industries generally they would bear witness in a 
 startling manner to the amount of money which goes to 
 the Continent in this connection. With regard to the 
 chemical industry, vulcanite appliances, such as pumps, 
 rods, tubes, etc., are used more particularly in the manu¬ 
 facture of fine chemicals for pharmaceutical purposes, a 
 branch which has never attained in Great Britain the 
 importance it has assumed in Germany; therefore, before 
 the rise of the electrical industry, there was no great induce¬ 
 ment to British rubber manufacturers to take up the 
 branch. Another and more important point is that the manu¬ 
 facture, particularly as regards the polishing of the material, 
 is by no means generally understood. The polishing of 
 vulcanite goods is an art, and the exact details necessary 
 for complete success must be considered even at this day to 
 come in the category of trade secrets. But supposing that 
 the methods followed are known to all, the cheap home 
 labour by which the polishing of the goods has been so 
 largely carried out in Germany in the past has not been 
 available to British producers. At the present day the art 
 of polishing vulcanite is not of quite the same importance as 
 in the early days of the industry when vulcanite jewellery 
 was so much in demand. In many cases to-day, notably 
 for battery cells, the polishing process is dispensed with, 
 the cost of the article being thereby greatly reduced. Of 
 special note in the vulcanite manufacture is the firm of Dr. 
 Heinrich Traun und Sohn, of Hamburg, in which the 
 
VULCANITE. 
 
 251 
 
 Harburg Gummi Kamm Company is now absorbed. The 
 firm recently celebrated their fiftieth anniversary, and in an 
 interesting brochure showed the rise and development of 
 this industry, with which alone they are concerned. Vul¬ 
 canite is made also in Russia, Austria, Hungary, Belgium, 
 Italy, and the United States—where the first factory, now the 
 American Hard Rubber Company, was established over fifty 
 years ago. With regard to the actual manufacture, which has 
 been stated to much resemble that of soft rubber goods, each 
 firm has it own special compounds, and products are to be 
 met with consisting not only of rubber and sulphur, but 
 containing in addition many of the chemical substances 
 already mentioned in the chapter on compounding, besides 
 others, such as resins, not there enumerated. In the mixing 
 process it is essential that all the materials be absolutely 
 dry, if the grave defect of porosity is to be avoided. The 
 proportions of rubber and sulphur used depend upon the 
 degree of rigidity required in the finished goods, in some 
 cases a certain amount of elasticity being wanted, while in 
 others material hard enough to be worked in the lathe is 
 the object. Reference to the use of resins shows that the 
 employment of Para rubber is by no means necessary; and, 
 indeed, it was very early found that East Indian brands of 
 rubber were most generally suitable for the manufacture. 
 For the vulcanization metal moulds are generally used, and 
 the lining of these with tin foil has been found an aid to 
 the subsequent polishing. The vulcanizing pans and 
 presses are similar to those already described, though the 
 time required is longer, anything, in fact, from 6 to 12 
 hours, and the temperature may be as high as 330° F. In 
 the polishing process the emery wheel is largely used ; also 
 
252 
 
 INDIA-RUBBER. 
 
 felt and other fibrous materials, alone or in conjunction 
 with fatty matters. 
 
 With regard to the physical properties of vulcanite, 
 atmospheric air has no oxidizing effect upon it, nor has 
 sunlight the injurious action that it has upon soft rubber. 
 Though impervious to electricity, it becomes charged with 
 static electricity when friction is applied to it. In boiling 
 water it softens, a property which is taken advantage of in 
 the manufacture of small articles from sheet vulcanite. It 
 is quite unacted upon by the ordinary rubber solvents, 
 including heavy oils, while only the strongest mineral acids 
 have any action. Exposure to a temperature exceeding 
 400° P. causes carbonization without any intermediate 
 stage of sticky decomposition. 
 
 As in the case of the ordinary rubber manufacture, old 
 and waste material comes up for use again after it has been 
 ground to a fine powder. 
 
 The manufacture of vulcanite ornaments is not now of 
 much importance, although it has been brought to a high 
 degree of perfection. In this work the object to be copied 
 or any new design is moulded in plaster of Paris, and 
 rubber solution mixed with sulphur is put into the mould. 
 It is customary to use bisulphide of carbon as the solvent, 
 and to add the solution in small quantities at a time to 
 allow of the evaporation of the solvent. When the mould 
 is full it is submitted to steam vulcanization for about ten 
 hours at four atmospheres pressure. 
 
 The material known as semi-vulcanite is, as its name 
 implies, a half-way product between ordinary vulcanized 
 rubber and vulcanite. It contains more sulphur than the 
 former, but less than the latter, and its various grades of 
 
VULCANITE. 
 
 253 
 
 plasticity depend upon the details of the vulcanization. It 
 is in request for certain uses in chemical works ; also for 
 insulating purposes, where its capacity for being bent is of 
 importance. A special insulating product of this kind has 
 been brought out by Messrs. Pirelli et Cie. 
 
CHAPTER XXL 
 
 CONTRACTS FOR INDIA-RUBBER GOODS. 
 
 Large buyers of rubber goods, such as the Admiralty, 
 War Office and other Government Departments, the various 
 railway companies, and the London County Council, have 
 their own specification forms, which are sent out to the 
 manufacturers once a year. A common form of wording 
 initiated many years ago by the Admiralty is as follows. 
 The rubber must be fine Para, without any admixture of 
 oil substitutes. In the case of the Government Depart¬ 
 ments the exact proportions and nature of the mineral 
 matter to be used are specified, as also the proportion of 
 sulphur. The railway companies and other corporations up 
 to recent times usually contented themselves with specifying 
 that pure Para must be the only rubber used. Now, there is 
 nothing whatever to say against this procedure where Para 
 rubber is really wanted, and where there is no rooted objec¬ 
 tion to paying the price that the market quotation of such 
 rubber renders obligatory; but as years went on, it became 
 increasingly evident to the rubber manufacturers that the 
 specifications in many cases were not intended to be read 
 seriously, or at all events, if they were, that no efforts were 
 made by the purchasers to see that the requisitions were 
 being complied with. It will be at once seen that this state 
 
CONTRACTS FOR INDIA-RUBBER GOODS. 255 
 
 of affairs was all against the honest trader. Those who 
 quoted for fine Para rubber were told that though the 
 quality received was all right, the price was much higher 
 than that of others who no doubt quoted for an inferior 
 brand of rubber. In the case of the Government Depart¬ 
 ments the best rubber was really required, and if goods 
 passed muster which were not of this standard the cause 
 must be attributed either to supineness on the part of 
 officials or to the inadequacy of the chemical tests adopted. 
 With regard to some, at any rate, of the goods required by 
 railway companies and others, it is clear that all Para 
 rubber is not required, and that there is no intention 
 of paying for it. Under these circumstances it is strange 
 to find it specified for, and it can only be attributed to the 
 ignorance or slackness of those responsible for the drafting 
 of the specification forms. Indeed, the author was told 
 by one official that he had inserted it because he had seen 
 it elsewhere, and thought it looked well. Leaving out of 
 account altogether the rather complicated question as to 
 whether the best Para is necessary for railway mechanical 
 goods, there can be no question as to the desirability of the 
 purchaser insisting upon his specified requirements. If 
 Para rubber is specified, let him see that he gets it; and if, 
 on the other hand, he is not really particular as to quality, 
 looking with a lenient eye upon palpable defects provided 
 the price is low enough, it would be far better to have the 
 reference to Para rubber deleted. This would make it 
 plainer sailing for the manufacturer, who otherwise stands 
 on the horns of a dilemma. By not using Para rubber he 
 is neglecting express injunctions, while on the other hand he 
 knows, with absolute certainty, as the heritage of experience, 
 
256 
 
 INDIA-RUBBER. 
 
 that if he does use it his tender will not he accepted 
 on account of price. This is where so much mischief is 
 wrought in the rubber trade generally : it is such a simple 
 matter to cheapen goods by a few pence per lb., that unless 
 a certain standard of quality is strictly insisted upon by the 
 buyer there is no saying to what degree of cheapening a 
 manufacturer may not feel compelled to go in order to 
 satisfy himself that he is in the running for a contract. 
 “If I do not quote for a low quality, assuredly my competitor 
 will,” he soliloquises, when casting his eye over the clause 
 of the specification referred to. So he proceeds to make 
 and submit samples, presumably to the standard of the 
 venerable specimen which may he inspected (through glass) 
 at the stores of the company. These sealed samples, it 
 must be confessed, are not really much of a guide to steer 
 by, mere inspection affording little indication of quality. 
 Defects in some classes of rubber goods are perceptible at 
 once to the sight, but this cannot be said of rubber goods 
 generally. It is axiomatic that the nearer we approach to 
 a thing the more conscious we become of its imperfections; 
 but in the case of inferior rubber goods disenchantment 
 is not always the product of propinquity, and recourse to 
 certain chemical and physical tests is necessitated. Where 
 this cannot be done the manufacturer is obviously placed 
 at a disadvantage, a circumstance which may easily affect 
 the best interests of the buyer as well as his own. In 
 these days, when the supposed secrets of the rubber 
 manufacture are now to a very large extent public property, 
 there seems no reason why a sample of the goods required 
 should not be issued to any bond-fide contractor, a reason¬ 
 able fee being charged for this privilege. With regard to 
 
CONTRACTS FOR INDIA-RUBBER GOODS. 257 
 
 some sealed samples and patterns which have done duty for 
 a considerable number of years, it is notorious in the trade 
 that they are more suited to adorn the cases in an 
 archaeological museum. Laxity or oversight on the part of 
 those responsible has led to their retention, though they 
 do not at all correspond to the spirit of the specification 
 form in current use. 
 
 With the wider spread of chemical analysis, and with the 
 more general knowledge regarding the price of raw rubber, 
 there has been discernible of late a disposition on the part 
 of large buyers of rubber goods to face the matter of prices 
 fairly, and to recognise that if good rubber is wanted, it 
 must be paid for. Even with the price of rubber 2s. per lb. 
 higher than it was five years ago, this tendency, which 
 showed itself a few years ago, has experienced no set back. 
 Indications are not wanting, for instance, that the reign 
 of the cheap buffer at bed-rock prices is nearly over; 
 it has been borne in upon the minds of the purchasers of 
 these goods that the removal of the pieces of the buffer after 
 it has been in use for a short time is an additional expense 
 which should be debited to the original cost. Railway 
 coaches, unlike Phaeton’s car, are destined to run for more 
 than one day; and it cannot be considered sound policy to 
 make any part, or to include any fittings, of an ephemeral 
 nature. The futility of buying highly adulterated rubber 
 goods seems to have a more general recognition at the 
 present time than has hitherto been the case, and this 
 is to be welcomed both in the interests of the purchasers 
 and as tending to the removal of a stigma which has 
 been cast upon the trade by engineers and others who 
 remained complacently blind to the fact that adulteration 
 
 I.R. 
 
 S 
 
258 
 
 INDIA-RUBBER 
 
 was the inevitable and only outcome of the rage for 
 cheapness. 
 
 For some years past growing dissatisfaction had been 
 shown by many of our leading rubber manufacturers at the 
 laxity with which the reference to Para rubber in speci¬ 
 fications was regarded both by manufacturers and buyers. 
 This culminated a year or two ago in strong representations 
 being made to the Government departments chiefly concerned 
 by a deputation of the India-rubber Manufacturers’ Associa¬ 
 tion. It was urged that as chemical tests did not distinguish 
 between fine Para rubber and second-grade Para rubber, or 
 any other high-grade rubber for the matter of that, the 
 specific reference to Para rubber should be omitted and the 
 term “best rubber ” substituted. At the same time it was 
 indisputably shown that the chemical and physical tests so 
 long relied upon by the Admiralty were insufficient for their 
 purpose, and did not in reality prove that only fine Para 
 rubber had been used. As showing the genuineness of the 
 agitation that had been aroused, it was suggested that the 
 existing tests should be altered so that only the best rubber 
 would conform to them. These representations met with 
 courteous consideration, and led to important alterations 
 in the specification form sent out by the Admiralty in the 
 autumn of 1902. The alterations will be duly dealt with in 
 the chapter on the testing of rubber goods, and it need only 
 be said here that their advent has been welcomed by those 
 who have the interests of the trade at heart. A far wider 
 circle, the British public generally, should also regard the 
 innovation with approval, as tending to efficiency both 
 in the goods purchased and in the routine of contract 
 placing. 
 
CONTEACTS POE INDIA-EUBBEE GOODS. 259 
 
 In many cases, no doubt, the best rubber procurable is the 
 cheapest in the long run: there are, however, cases where 
 a cheap rubber is not only desirable, but absolutely necessary 
 if efficiency is to be attained. The use of high-pressure 
 steam has led largely to the substitution of rubber in 
 packings by asbestos and other bodies which are not 
 destroyed by heat, and where rubber is still used it is 
 eminently undesirable to contract for it without taking into 
 due consideration the exact temperatures to which it is to 
 be subjected. There is more than a suspicion that sufficient 
 care has not been taken with regard to this point in drawing 
 up specifications for packings in which rubber is one of the 
 components, and it would certainly seem that the opinion of 
 manufacturers of repute might in cases of this sort be 
 invited with advantage. 
 
 The main article contracted for by the Admiralty is the 
 vulcanized compound rubber supplied in sheets out of which 
 valve washers, etc., are cut at the dockyards. In the case of 
 the War Office, the “ground sheet ” is the principal article 
 contracted for. This sheet, in which the soldier rolls him¬ 
 self, or which is made to serve as the floor of his tent, 
 consists of cotton cloth faced with compound rubber, 
 vulcanized. 
 
 In connection with Government contracts, it may be 
 mentioned that the Departments reserve the right to inspect 
 the work in progress, though it must be said that the official 
 visits are neither frequent nor very inquisitorial. Inspection 
 in the course of manufacture is also stipulated for by some 
 of the consulting engineers in London who buy for Indian 
 and Colonial Railways ; it is not on record, however, that 
 the young mechanical engineers who carry out this duty 
 
 s 2 
 
260 
 
 INDIA-RUBBER, 
 
 do more than cut off an occasional sample to forward to 
 headquarters. 
 
 Among other contractors who supply the rubber manu¬ 
 facturer with the formulae on which he is to work are those 
 insulated cable makers who have been already mentioned in 
 a previous chapter. 
 
CHAPTER XXII. 
 
 THE TESTING OF INDIA-RUBBER GOODS. 
 
 Considering the importance of this subject ancl the 
 developments which it has witnessed in recent years, the 
 author feels no hesitation iu devoting a chapter to its con¬ 
 sideration, especially as it forms a useful sequel to what 
 has just been said about contracts. The application of 
 chemical and physical tests to india-rubber goods, though 
 more general at the present time than in the past, is 
 naturally limited to such buyers as have at their disposal 
 laboratories or testing shops. Some small purchasers there 
 may be who submit samples to an outside analyst or con¬ 
 sultant before concluding their purchases ; but these are 
 few in number, and the bulk of small buyers are not 
 unnaturally indisposed to go to the expense of having 
 analyses made, preferring rather to trust to the manu¬ 
 facturers’ reputation and honesty. 
 
 It is not so many years ago that the test of specific 
 gravity, or, to speak more precisely, of relative density, was 
 the only one applied by the majority of purchasers of 
 mechanical rubber goods, such as valves and washers. The 
 mill engineer used to throw his valve into the water tank 
 to see whether it floated or sank. This test was never a 
 very satisfactory one, and it became of even less value 
 when the advent of oil substitutes made it possible to 
 
262 
 
 INDIA-RUBBER. 
 
 adulterate rubber largely without destroying its capacity 
 for floating. There are, indeed, secluded places even at the 
 present day where the light of modern knowledge has not 
 yet penetrated, and where the engineer buys rubber goods 
 on tests quite as crude and unsatisfactory as the above, 
 though possibly not identical with it. Yet indiscriminate 
 opprobrium should not be heaped upon the practical man 
 who essays by simple tests to ascertain the value of his 
 purchases. His experience has shown him, no doubt, that 
 chemical analysis can be sadly at fault as a guide and 
 mentor in these cases. Even the expert rubber analyst— 
 as distinguished from the general analyst to whom such 
 goods are often submitted—is unable to detect faulty work¬ 
 manship which may lead to premature decay of the goods 
 when in use. The analysis, indeed, may show the nature of 
 the ingredients and their proportions to conform to a 
 recognised standard, but it may fail to give further informa¬ 
 tion which is of the utmost importance with regard to pre¬ 
 dicting the life of the goods under the special conditions of 
 their employment. Amongst large buyers, therefore, it is 
 now customary to supplement chemical analysis by physical 
 tests specially devised for the purpose of ascertaining the 
 suitability of the goods. The chief danger to be appre¬ 
 hended here is the adoption of unsuitable tests, particularly 
 those which err on the side of severity. For instance, goods 
 which are intended to be used only at normal temperatures 
 should not be exposed to high temperatures such as are 
 used to test the reliability of steam packings. This in a 
 general sense ; there may, of course, be cases where the 
 expert employs the results of high temperature tests in 
 order to corroborate figures obtained in other ways. What 
 
THE TESTING OF INDIA-RUBBER GOODS. 
 
 263 
 
 it is intended to convey is a warning against the indis¬ 
 criminate adoption of tests which have been specially 
 devised for certain classes of goods to which alone they are 
 legitimately applicable. A drawback which is often urged 
 against chemical analysis is that the taking of the necessary 
 samples means cutting or defacing the goods; there is also 
 the further consideration that the part so taken may not be 
 truly representative of the whole. The question of segrega¬ 
 tion of constituents which is here opened up is of too 
 abstruse a nature to claim consideration in the present 
 volume ; it can only he hinted at as a possible explanation of 
 discrepancies in figures obtained by different analysts. 
 
 In the previous chapter reference has been made to 
 recent alterations in the Admiralty tests for rubber. The 
 original tests which did duty for many years were one 
 hour’s dry heat at 270° F., and three hours’ moist heat at 
 320° F. In 1902 the latter test was changed to four hours 
 at 320° F., and in 1905 was substituted altogether by a 
 chemical test which had already for some years been 
 largely adopted on the Continent. As this test is one of 
 considerable importance, it seems of interest to give the 
 entire clause in which it occurs in the specification, which 
 relates to what are known as A-quality goods 
 
 “ The india-rubber is to be made of pure caoutchouc of 
 the quality specified below, with no other ingredients than 
 sulphur and white oxide of zinc. The sulphur is not to 
 exceed 3 per cent., and the oxide of zinc is not to exceed 
 40 per cent., reckoned on the manufactured rubber. It is 
 to be of a homogeneous character throughout, and is to be 
 thoroughly compressed, free from air holes, pores and all 
 other imperfections ; it must contain no crumb rubber, 
 
264 
 
 INDIA-RUBBER. 
 
 recovered rubber, or other treated or waste rubber, or 
 rubber substitute of any kind. It must endure a dry 
 beat of 270° F. for two hours without impairing its quality. 
 The quality of the caoutchouc used must be of such a 
 character that after it has been made up into the vulcanized 
 and finished article, as defined above, not more than 10 
 parts per cent, of organic matter and sulphur calculated on 
 the non-mineral matter present can be extracted from the 
 rubber by boiling it for six hours, in a finely-ground con¬ 
 dition, with a 6 per cent, solution of alcoholic potash.” 
 
 The exact meaning of this test seems to have occasioned 
 some little difficulty in the minds of those reading it hastily ; 
 but in reality there is nothing ambiguous about it, and its 
 tenour should make itself clear to those who study it with a 
 little attention. 
 
 If one might suggest a still further point of advance, 
 this is in the direction of the issue of detailed instructions 
 as to how these tests are to be carried out in the laboratory. 
 It is quite conceivable that in the case of the heat test 
 different opinions should be arrived at; not only should the 
 arrangement of the air bath be identical in the case of both 
 buyer and seller, but the exact meaning of “ impairing its 
 quality ” should be given, as otherwise the deductions drawn 
 by different observers are apt to be affected by the personal 
 equation. Still, one must not expect perfection to be 
 achieved all at once, and at any rate the new tests are 
 generally admitted to be a decided advance upon the old 
 ones, and to be in the interests of fair dealing. The idea of 
 the tests is, of course, to cause the detection of any rubber 
 which is not of the highest quality, and the specification as it 
 stands at present gives much more scope to the manufacturer 
 
THE TESTING OF INDIA-RUBBER GOODS. 
 
 265 
 
 who wishes in a perfectly legitimate way to get the best 
 of his competitors. It is by no means certain that fine 
 Para only will pass the test, and as all other rubbers 
 are cheaper it may prove possible to make combinations as 
 the result of careful experimenting such as will put the 
 manufacturer who possesses himself of the golden thread in 
 a position unassailable by his competitors. 
 
 The topics that offer themselves for treatment in this 
 chapter are too numerous to allow of individual mention, 
 and a selection must perforce be made. India-rubber 
 solution, which is largely dealt with in the Carriage Depart¬ 
 ment at Woolwich Arsenal, has to contain at least 18 per 
 cent, of rubber. In addition to determining the amount of 
 rubber present a mechanical test is made by solutioning 
 two pieces of canvas cloth together, and then ascertaining 
 the mechanical power required to tear them asunder. For 
 a figure and description of the particular machine employed 
 in this test, and for the testing of fabrics generally, the 
 reader is referred to Weber’s book on the chemistry of 
 india-rubber. Another test in use by the War Office is in 
 connection with indigo-blue cloth; this has to stand boiling 
 for ten minutes in a dilute sulphuric acid solution, by which 
 means any substitution of logwood for the more expensive 
 indigo is at once detected. Turning now to the railway 
 companies, it is common procedure on their part to submit 
 samples of all deliveries of carriage and wagon buffers to 
 mechanical tests, any failure rendering the whole consign¬ 
 ment liable to rejection. This testing on a large scale of 
 course takes time, and involves, in addition, the purchase 
 of rather expensive machinery ; but there is no doubt that 
 it pays the buyer. Without going into great detail it may 
 
266 
 
 INDIA-RUBBER. 
 
 be said that the buffer-testing machine is on the principle of 
 the stamp commonly used in gold mining, five or six 
 hammers being worked by a cranked axle and striking 
 blows on as many buffers. The superficial dimensions of 
 the buffer springs are carefully measured both before and 
 after the test, which may consist of 1,000 to 10,000 blows, 
 and which may last the whole day. A good buffer should 
 measure the same after as before the test, though one of 
 inferior quality, he., wanting in elasticity or badly vulcanized, 
 will be found to have sustained a permanent set after the 
 test. It will be recognised at once that this test is of more 
 value than any chemical one would be, and naturally it puts 
 the rubber manufacturer on his mettle, as it is no easy task 
 to get such an equality of vulcanization as is requisite. It 
 is no doubt a fact that there are variations in the elasticity 
 and strength of rubber which cannot be detected in the 
 ordinary course of business. This being granted, it need 
 cause no surprise that the tests made by the railway com¬ 
 panies occasionally lead to the rejection of buffers which the 
 makers had every reason to suppose were exactly similar to 
 previous deliveries which had passed the same test satis¬ 
 factorily. Special reference is made to this, because it is 
 easy for an engineer to jump to the false conclusion that 
 some adulteration has been practised, when nothing of the 
 sort has been attempted. Though not exactly coming 
 within our present subject, it maybe remarked that there is 
 a strong tendency to revert to the steel spring as a substitute 
 for the rubber buffer whose vagaries we are now considering. 
 The following figures were obtained by a railway company 
 from a delivery of buffers, all supposed to be of equal 
 quality, and they show conclusively that some variation 
 
THE TESTING OE INDIA-RUBBEB GOODS- 
 
 267 
 
 either in the quality of the rubber or in the method of 
 manufacture had occurred :— 
 
 
 Loss after Plates. 
 
 Loss after 10,000 
 Machine Blows. 
 
 
 Per cent. 
 
 Per cent. 
 
 1 
 
 Nil. 
 
 50 
 
 2 
 
 ? ? 
 
 39 
 
 3 
 
 
 19 
 
 4 
 
 ,, 
 
 25 
 
 5 
 
 
 10 
 
 i 
 
 2 
 
 48 
 
 2 
 
 8 
 
 43 
 
 3 
 
 17 
 
 36 
 
 4 
 
 7 
 
 45 
 
 The loss after plates refers to the permanent decrease in 
 thickness noticed after the buffers have been screwed up 
 under pressure for a length of time between iron plates, 
 and the percentage of loss after the machine blows indi¬ 
 cates the decrease in lifting power, or, in other words, 
 of elasticity. For example, a buffer which will lift a 
 weight of six tons before undergoing the machine blows, 
 and only three tons afterwards, shows a loss of 50 per 
 cent. It is quite exceptional for a delivery of buffers 
 to show such great variations as are given in the table, 
 but the figures show the value of the test from the 
 railway engineer’s point of view. Other railway goods, 
 such as the diaphragms used in connection with the auto¬ 
 matic vacuum brake, hose for steam heating, etc., cannot 
 be so satisfactorily tested, though a system of testing high- 
 pressure steam tubing by attaching two or three lengths to 
 steam jets, and comparing their behaviour under known 
 
268 
 
 INDIA-RUBBER. 
 
 pressures, has accorded useful indications as to suitability 
 and probable longevity. The subject of physical tests for 
 railway mechanical rubber goods has received closer attention 
 in America than in England; but there is a feeling among 
 the rubber manufacturers that the prescribed tests now to 
 be found in so many specifications are altogether too severe, 
 and that close observance of them leads to unnecessary 
 expense, though naturally this does not fall on the manu¬ 
 facturer. For instance, air-brake hose must stand a pressure 
 of 200 lbs. for ten minutes before bursting. In what is 
 known as the friction test, a section one inch long is taken 
 from any part of the hose and the friction, or tenacity 
 between the rubber and fabric, determined by the force and 
 time required to unwind the hose, the force to be applied at 
 right angles to the line of separation with a weight of 
 28 lbs. suspended from the separated end, and the average 
 speed of unwinding not to exceed six inches in ten minutes. 
 
 There are certain classes of goods which have to with¬ 
 stand abrasion from contact with rough surfaces. By far 
 the most important of such goods, as regards the amount of 
 money involved, are motor tyres, and a good deal of trouble 
 has been taken of late in devising a satisfactory method of 
 mechanical testing. It is safe to say that perfection has 
 not yet by any means been attained, but the progress made 
 is not inconsiderable. Although the different tyre manu¬ 
 facturers may vary their processes in points of detail, they 
 all, as far as the author knows, use the application of friction. 
 At a recent motor show in Germany, a well-known German 
 tyre was set to run continuously on broken flints, the 
 arrangement of the mechanism being that the tyre remained 
 stationary while the road took the form of an endless band 
 
THE TESTING OF INDIA-RUBBER GOODS. 
 
 269 
 
 in continuous motion. At the large rubber works of the 
 Russian-French Company at Prowodnik-Riga, the testing 
 of solid cab tyres has received considerable attention. The 
 plan generally adopted is to fix four tyred wheels to arms 
 radiating from a central axis, in this case the tyres revolv¬ 
 ing over a fixed flint bed. It is claimed that such friction 
 tests not only distinguish between the value of the different 
 kinds of rubber for tyre purposes, but that they also serve 
 to detect irregularities in the manufacture. 
 
 It would occupy too much space to discuss at length the 
 pros and cons, of these tests; moreover, as has been stated 
 things are really only in an initial stage. The subject, 
 therefore, will be dismissed with the remark that continuous 
 testing of rubber on rough surfaces varies from what 
 obtains in practice, as the tyres which become hot on run¬ 
 ning have no time to cool down, as occurs when they run 
 intermittently. 
 
 With regard to rubber heel pads, it is sought to get an 
 index of their wearing capacity by the abrasive action of an 
 emery wheel. By this means the difference between an 
 elastic rubber and one which is heavily compounded is at 
 once seen. The test, however, must be applied with caution 
 and with due regard to circumstances of price. Where time 
 allows of it, it seems on the whole preferable to make a trial 
 on the heel of some active pedestrian. 
 
 Mention may be made of a chemical test to estimate the 
 liability of vulcanized rubber goods to undergo atmospheric 
 oxidation. This test, as proposed by C. 0. Weber, consists 
 in immersing a weighed strip of the rubber—for instance, 
 a motor or cycle tyre—in a solution of hydrogen peroxide 
 in acetone. After two days the rubber is removed, dried 
 
270 
 
 INDIA-RUBBER. 
 
 and weighed, any increase in weight being due to absorption 
 of oxygen. More recently Ditmar 1 has investigated the 
 process and suggested an alteration in procedure, though it 
 cannot be said that the alteration makes for simplicity or is 
 likely to at once carry conviction to those who have looked 
 upon Weber’s method with some degree of suspicion as to 
 its general reliability. 
 
 1 Gummi Zeitung. 
 
CHAPTER XXIII. 
 
 GUTTA-PERCHA. 
 
 There is a somewhat prevalent idea that india-rubber and 
 gutta-percha are practically identical bodies, though this is 
 by no means the case. Not only are the substances yielded 
 by totally different trees, but they also show a wide diver¬ 
 gence in their properties and it is only in rare cases that 
 the one can replace the other. John Tradescant, an English 
 traveller, is credited with having brought the first sample 
 of gutta-percha to England in 1656, but it was not until 
 1882 that the substance really attracted any attention. This 
 was brought about primarily by the investigations made 
 into its occurrence and properties by William Montgomery, 
 a British surgeon resident at Singapore, a place afterwards 
 destined to become the headquarters of a large export 
 industry. In a letter written in 1848 to the Medical Board 
 at Calcutta, he details the advantages which the new body 
 was found to possess over india-rubber for certain surgical 
 purposes. Details of his work were shortly sent to London, 
 and Montgomery was awarded the gold medal of the Society 
 of Arts. Not long afterwards the botanical side was investi¬ 
 gated by Dr. Oxley, the tree being christened by Sir William 
 Hooker Isonandra Gutta. The substance at once attracted 
 considerable attention in England and France, various 
 
272 
 
 INDIA-RUBBER. 
 
 patents being taken out in connection with proposed appli¬ 
 cations. Most of these were doomed to failure as they did 
 not take into sufficient consideration the physical properties 
 of the substance; these properties, while rendering it 
 eminently superior to rubber for some purposes, being at 
 the same time a bar to its general use in cases where 
 rubber had already established itself in an impregnable 
 position. 
 
 Recent research has added largely to the known number 
 of species of trees which yield gutta-percha, but the pro¬ 
 ductive area has only been very slightly extended by those 
 botanists and travellers who have made the trees a special 
 object of search. While india-rubber has been shown to 
 occur generally in a broad equatorial belt, gutta-percha is 
 only to be found in a much more restricted area, the total 
 production coming from what may be roughly described as 
 the Straits Settlements and the Malay Archipelago ; Borneo, 
 Sumatra, the southern end of the Malaccan Peninsula, 
 Java, the Celebes and Sulu Islands being the principal 
 gathering grounds. Of interest in this matter of supply is 
 the statement recently made by Dr. Sherman, of the local 
 Forestry Department, to the effect that the gutta trees are 
 abundant in certain parts of the Philippine islands. From 
 his further remarks there seems little doubt that the 
 substance has long been obtained from the Philippines by 
 Chinese merchants who kept quiet as to its point of origin 
 when they sold it at Singapore. It might not prove of 
 much general interest, even if space permitted, to treat the 
 botanical side of our subject at length, and those who are 
 specially interested may be referred to Leon Brasse’s 
 great work and to the excellent chapters in the English 
 
GUTTA-PERCHA. 
 
 273 
 
 translation of Clouth’s book, or to Dr. Obach’s papers. It 
 will suffice here to give the main features of the raw gutta¬ 
 percha industry. The trees belong to the Sapotacese family 
 the Isonandra, or as it is now generally called, the Dichopsis 
 gutta, being a prominent species, while the Dichopsis oblongi- 
 folium follows it closely as regards quality of product. Full 
 grown trees have the trunk one to two yards in circum¬ 
 ference, though the collectors by no means limit their work to 
 those which have attained maturity. The gutta-percha occurs 
 as a milky latex in the bark, and is always obtained by 
 cutting the tree down and allowing the latex to drain into 
 receptacles placed under cuts. The latex, which is called 
 su su in North Borneo, is coagulated by being poured into 
 boiling water. The whole business which is in the hands of 
 Chinese merchants and native collectors is carried on in a 
 very wasteful and unscientific manner. Good and inferior 
 qualities of latex obtained from different trees are indiscrimi¬ 
 nately mixed together, and very little of what comes upon 
 the European markets can be attributed to a particular 
 species of tree. Not that the mixing is always done 
 haphazard, for experienced collectors know how to avoid 
 reducing the quality of first-class material. 
 
 Owing to the destructive method of collection—for not 
 only is the tree felled but large amounts of latex are invari¬ 
 ably left in it to be wasted—it has long been clear that a 
 famine is merely a matter of time. Comparatively little 
 has been done in the way of gutta-percha plantations, and 
 the results so far achieved go to show that the cultivation 
 is not only hedged round with difficulties but also that, 
 compared with rubber, a much longer time must elapse 
 before any return is obtained from invested capital. To 
 
 I.R. 
 
 T 
 
274 
 
 INDIA-RUBBER. 
 
 the best of their ability the British and Americans who are 
 in authority in the producing areas, have sought to grapple 
 with the situation by putting restrictions upon the felling 
 of the trees. But as in certain rubber producing areas 
 already referred to, it is no use putting up prohibitory 
 notices unless there is a sufficient police force to see that 
 the law is respected. The great difficulty in the matter is 
 that no alternative procedure to the felling of the trees 
 yields results which the collectors consider satisfactory. A 
 great deal has of course been done in recent times with 
 regard to extracting gutta-percha from twigs and leaves by 
 volatile solvents. When the material, however, can be got 
 much more easily, the natives are unlikely to trouble them¬ 
 selves with complex chemical operations, and although the 
 processes worked out by Serullas, Jungfleisli, Ramsay, 
 Obach, etc., worked right enough, they have certainly not 
 proved a commercial success where they have been tried in 
 Europe, though satisfactory results have been obtained by 
 the Dutch Company extracting gutta-percha from leaves at 
 Singapore. The solvent which is said to give the best 
 results is toluol, the process consisting simply of digesting 
 the pulverized leaves, twigs, bark, etc., in it at about the 
 boiling point of water and in evaporating the solvent off in 
 a current of steam, as direct distillation injures the product. 
 The residual gutta-percha has a greenish colour owing to 
 chlorophyll, the green colouring matter of the leaves, and 
 is said to have been highly spoken of by experts. The pro¬ 
 cess has been worked in France, but to the best of the 
 author’s knowledge is not now in operation, while the 
 disastrous career of the British Company, formed with a 
 large capital to work the extraction, hardly needs reference. 
 
GUTTA-PERCHA. 
 
 275 
 
 But whatever potentialities these extraction processes may 
 have, it seems clear that they cannot be reckoned upon as 
 any immediate solution of the threatened famine, and it 
 wmild seem that salvation can only come through such 
 channels as Government control. It is expected that in the 
 Philippines regulations will be made whereby collectors will 
 have to obtain licences and be compelled to conform to pro¬ 
 cedure calculated to prevent destruction and waste. Such 
 efforts will assuredly be watched with interest by those who 
 foresee a shortage of supply should any great submarine 
 cable scheme come into existence. So much for the supply, 
 and now a word as to the raw material as it comes to Europe. 
 The reddish white lumps of varying size always contain 
 chips, bits of bark and water as impurities which are 
 removed sufficiently for common purposes by maceration in 
 hot water after being cut into small pieces. For insulating 
 purposes it requires a more thorough cleansing, which is 
 carried out in a special form of washing machine in which 
 it is both shredded and squeezed in warm water, at the 
 bottom of which the impurities collect. It next goes to the 
 kneading mill, consisting of a fluted shaft revolving in an 
 iron cylinder and afterwards to a strainer where it is forced 
 through fine wire gauze. The gutta-percha, which at the 
 end of these processes should be free from mechanical 
 impurities, water and air, is rolled out, cut into sheets and 
 stored ready for use. 
 
 Gutta-percha has a specific gravity just above 1, and 
 compressed specimens will sink in water. Chemically 
 it consists of a hydrocarbon of the same formula as 
 india-rubber with variable quantities, of two peculiar 
 resins named albane and fluavile. Payen who appears 
 
 t 2 
 
276 
 
 INDIA-RUBBER. 
 
 to have been the first to investigate them, gives the 
 proportions as 
 
 Gutta 
 
 78 
 
 Albane 
 
 16 
 
 Fluavile 
 
 6 
 
 
 100 
 
 According to Ondemans who investigated these bodies 
 closely, fluavile is a soft yellow resin becoming fluid at 210- 
 230° F., while albane is a white crystalline resin becoming fluid 
 at 320° F. The chemistry of these bodies has recently been 
 re-investigated by Sir W. Ramsay and others, 1 whose 
 experiments showed the extreme susceptibility of the gutta 
 hydrocarbon to oxidation. Of more general interest will be 
 the following analyses of raw gutta-percha taken from 
 among the numerous figures published by Obach :— 
 
 Brand. 
 
 Gutta. 
 
 Resin. 
 
 Dirt. 
 
 Water. 
 
 Pahang . 
 
 78-1 
 
 19-2 
 
 lo 
 
 1-2 
 
 Banjer red 
 
 47-0 
 
 30-2 
 
 1-5 
 
 1-3 
 
 Bulongan red 
 
 68-6 
 
 29-0 
 
 1-4 
 
 1 0 
 
 ,, white 
 
 Banjer white . 
 
 52-2 
 
 45 - 4 
 
 1-5 
 
 0-9 
 
 51-8 
 
 44'1 
 
 1-8 
 
 2-3 
 
 Sarawak mixed 
 
 oo'6 
 
 40-9 
 
 1-8 
 
 1-7 
 
 Banca reboiled 
 
 46-8 
 
 51-1 
 
 1-1 
 
 1-0 
 
 The main feature about gutta-percha which distinguishes 
 it sharply from india-rubber, is its plasticity under heat. 
 At a temperature about 100° F. it softens; thus if a piece 
 is put into water which is being gradually heated, it gets 
 more and more plastic until at about 190° F. it can be 
 moulded or drawn out into forms which it will retain on 
 1 Jour. Soc. Chem. lad., 1902. 
 
GUTTA-PERCHA. 
 
 277 
 
 cooling. In this respect, india-rubber as we have seen 
 behaves quite differently, and this property alone is quite 
 enough to dispose of any idea that they are identical. As 
 regards the action of solvents, of acids, and of alkalies, the 
 two substances are much the same, differences being 
 confined to points of minor importance. Although to some 
 extent it has a cellular structure, gutta-percha is not porous 
 to water as rubber is, and it is this which makes it such a 
 valuable insulator for submarine cables. Exposed to the air 
 it rapidly undergoes oxidation, the extent to which this takes 
 place having been shown by Miller in 1856. In the oxidized 
 state it has the form of a hard resin, its original tough¬ 
 ness being entirely lost. The best way to preserve gutta¬ 
 percha is to keep it under water, and at any rate it should 
 not be exposed to sunlight. Although it has many and 
 varied applications in the arts where it is utilised by 
 chemical manufacturers, surgeons, dentists, upholsterers, 
 hatters, fuse makers, etc., the great bulk of the gutta-percha 
 coming to England finds its way to the great cable works 
 on the Thames, the golf ball manufacturers probably being 
 the next largest consumers. For the cable manufacture, 
 great care is exercised in selecting certain brands of gutta¬ 
 percha or in mixing the different brands, so as to obtain a 
 material of high insulating power, there being considerable 
 differences in this respect in the various qualities. The 
 exact procedure followed is the outcome of the experience 
 gained by the experts engaged in the large cable factories, 
 and comes within the category of trade secrets. With 
 regard to the application of the insulation to the wires, this 
 is simple enough it being applied in the melted condition to 
 the wire core as it passes through the die of a machine very 
 
278 
 
 INDIA-RUBBER. 
 
 similar to the tubing machine referred to earlier. Wires 
 are also covered by being placed between two strips of gutta¬ 
 percha, the whole being then passed between two polished 
 grooved rollers. 
 
 The total length of deep sea gutta cables is said to be now 
 over 200,000 nautical miles, the cost of construction being 
 variously given as 150 1. to 200b per mile. 
 
 For the golf ball manufacture the gutta-percha has to be 
 hardened by the extraction of its resins, this being done by 
 soaking it in tanks of light petroleum spirit. By this means 
 the resins can be reduced to about 2 per cent., the purified 
 gutta then requiring a much higher temperature to soften it. 
 The advent of the rubber cored ball has largely reduced the 
 quantity of gutta-percha treated in this way, and a further 
 reference to this topic will be found under the head of balata. 
 
 Compared with the compounding of rubber with mineral 
 matter, nothing of the sort takes place in the gutta-percha 
 manufacture. Certainly, the late Mr. Dick of Glasgow, so 
 well known in connection with gutta-percha and balata, 
 describes some compounds, but these contained rubber as 
 well as mineral matter, and can hardly be called compounded 
 gutta-percha. Then with regard to vulcanization which one 
 author says is quite feasible, and which another says is 
 impossible, the truth seems to be that inventive genius in 
 several cases has produced a so-called vulcanized gutta¬ 
 percha by processes analogous to those employed with 
 rubber. The product, however, seems to have no particular 
 value, and to the best of the author’s knowledge vulcanized 
 gutta-percha has no practical applications. In saying this, 
 it must be on the footing of not being misunderstood. The 
 statement just made refers to gutta-percha alone, and not to 
 
GUTTA-PERCHA. 
 
 279 
 
 those particular compounds into which both rubber and gutta¬ 
 percha enter as component parts. Gutta-percha scraps and 
 cuttings can of course be used up again at once as new 
 material, no reclaiming process being required as with 
 vulcanized rubber scrap. Old material, such as is sold off 
 periodically by tender from the Post Office stores, depends 
 for its value very much upon the degree of oxidation it lias 
 undergone, it being found to vary considerably in this 
 respect. Since the introduction of the dry core paper 
 insulation, the use of gutta-percha in the subterranean 
 telephone circuits, especially in London, has much decreased, 
 though the author is unable to say by exactly how much 
 the figure of 17,000 miles computed some years ago for 
 London has undergone diminution. 
 
 Certain compounds, such as are well known in connection 
 with the name of Chatterton, and contain gutta-percha mixed 
 with Stockholm tar and resin, have a large application in the 
 insulation industry. Numerous other cements containing 
 gutta-percha have also been devised for special purposes. 
 
 With regard to substitutes for gutta-percha, trade litera¬ 
 ture is by no means barren, but there really seems to be 
 only one that has established itself and therefore calls for 
 mention. This is a German invention known as Gutta- 
 Gentsch, which has been favourably reported on by the 
 German Post-office, and has recently had a considerable 
 application in this country in connection with electric tram¬ 
 way cables. It consists of a special combination of 
 india-rubber, pitch, and resins, and is now being made in 
 England by the New Gutta Company, Limited. While its 
 insulating power is said to be quite equal to gutta-percha, 
 it does not oxidize like the latter in air, a point which is, 
 
280 
 
 INDIA-RUBBER. 
 
 of course, greatly in its favour for subterranean or serial 
 lines. With regard to its capabilities for replacing gutta¬ 
 percha in deep-sea work, it is somewhat early to speak with 
 confidence, but it may be mentioned that a short length of 
 deep-sea cable insulated with it was laid by Eelten and 
 Guilleamne in 1902 off the German coast. 
 
 Statistics of Gutta-percha Exports .—If any corroboration 
 were needed of the statement previously made, that the 
 bulk of the gutta-percha supply goes for the submarine 
 cable manufacture, it will be found in the export statistics 
 for particular years. Except in times when great activity 
 is witnessed in cable-laying schemes, the annual exports of 
 gutta-percha from Singapore amount to something between 
 6,000,000 lbs. and 9,000,000 lbs. In the years 1898 and 
 1899, however, the exports were considerably greater, owing 
 to the large cable-making companies in England putting 
 themselves in a position to contract for the forthcoming 
 all-British cable from Vancouver to Australia, and also to 
 the Germans having schemes of some magnitude on hand. 
 
 Thus the exports, in round numbers, rose from 
 6,000,000 lbs. in 1897 to 10,000,000 lbs. in 1898 and 
 16,000,000 lbs. in 1899. The destination in 1899 was:— 
 
 lbs. 
 
 Great Britain 
 Continental Europe . 
 United States 
 
 10,149,867 
 
 5,586,800 
 
 441,466 
 
 16,178,188 
 
 Since the completion of the all-British Pacific cable there 
 have been no schemes of any magnitude, and both exports 
 and prices have materially declined. 
 
CHAPTER XXIV. 
 
 BALATA. 
 
 This body is perhaps better known to engineers than to 
 other classes of the community by reason of the fact that 
 its principal application is in the manufacture of belting for 
 machinery. It occurs as a milky latex in the bark of certain 
 trees of the Sapotaceous order, and although in appearance, 
 composition, and properties, it is very similar to gutta¬ 
 percha, and was at one time supposed to be identical with 
 it, it has now for the last twenty-five years been recognised 
 as a distinct substance. It is yielded by several species of 
 Mimusop trees, of which it will suffice to mention the 
 Mimusops balata as the principal producer. This tree is 
 found in many equatorial regions, but to the greatest extent 
 in Venezuela, the Guianas, and the West Indies. It is from 
 these districts that the European market has been supplied, 
 and at the present time the business is limited to Venezuela 
 and the Guianas. Comparatively little of the output goes 
 to America, and probably it is this fact which led an 
 American author a few years ago to say that balata would 
 find more extensive employment if it were not so scarce. 
 Although it is not easy to give any accurate figures, owing 
 to the fact that it is lumped together with gutta-percha in 
 our trade returns, it is a fair assumption that the European 
 
282 
 
 INDIA-RUBBER. 
 
 imports total about 1,000 tons per annum. There is no 
 evidence that this quantity could not be largely increased if 
 the demand was greater and a remunerative price was 
 regularly obtainable. Outside the balata belting manufac¬ 
 ture the applications of balata have been kept somewhat as 
 trade secrets. How much or how little is used in the sub¬ 
 marine cable manufacture is a matter known only to those 
 immediately concerned, and the same thing may be said 
 with regard to the solid gutta golf ball. The latter has, of 
 course, been largely superseded by the rubber cored ball, 
 and just at the date of the wholesale manufacture of the 
 latter the author had inquiries from Venezuela as to what 
 was wrong with the balata trade in England, as the demand 
 had fallen off. This certainly looks as if it had been used 
 to a considerable extent in the golf ball manufacture in the 
 absence of evidence that any other industry employing 
 balata has been revolutionised. With regard to its present 
 applications, it is clear that an increasing quantity is being- 
 used in the belting trade, three new firms having quite 
 recently started on a large scale in England, as well as 
 others on the Continent. 
 
 To say a word or two now about the collection of the 
 substance. In Venezuela it is the custom to cut down the 
 tree and to let the latex run into vessels from the trunk 
 while in a horizontal position. This procedure is said to be 
 necessary owing to the very stagnant flow from cuts made 
 in the bark of the living tree. Although there may be a 
 good deal in this, we find that in the Guianas the felling 
 of the trees is the exception rather than the rule. As 
 Venezuela has of late years cut out the Guianas as a 
 producer, it looks as if the felling system was the more 
 
BALATA. 
 
 283 
 
 profitable for quick extraction and immediate profits, 
 though, of course, it takes no thought of the morrow. 
 Here the question arises as to how far conservative 
 measures are necessary, even if their application were 
 within the region of practical politics. There really seems 
 no reason to apprehend a shortage of supply, owing to the 
 comparatively limited demand and the well-known extent of 
 the balata bearing forests. Under the circumstances of 
 collection, it would be an extremely arduous matter to 
 enforce any enactments prohibiting the felling of trees or 
 to bring delinquents to justice. This would require police 
 supervision on a scale which the present resources of the 
 country would be inadequate to meet. Replanting of 
 denuded areas might, however, be made a matter of com¬ 
 pulsion, otherwise the greater distances which will have to 
 be traversed by collectors as time goes on must lead to a 
 rise in price. As it is, the merchants of Bolivar say that if 
 the price in England falls appreciably below two shillings 
 per pound the collecting and export cannot be carried on at 
 a profit. Like the Brazilian rubber collector, the Venezuelan 
 native has to force his way through the dense undergrowth 
 of the sunless forest, where the climatic conditions fre¬ 
 quently prove fatal even to those presumably inured to 
 them. The usual time for collection is in the wet season— 
 a reason which, in Venezuela, does not always adhere 
 strictly to its description. If the season happens to be 
 a dry one, the latex cannot be made to run at all from 
 incisions in the bark, and the trouble thus given, even 
 when the trees are felled, would be, of course, accentuated 
 were the felling prohibited. The number of those engaged 
 in balata gathering is by no means large, and this has led 
 
284 
 
 INDIA-RUBBER. 
 
 to a certain independence of spirit. When not collecting 
 on their own account, the natives hire themselves out to 
 merchants who supply a collecting expedition with the 
 necessary food and equipment for a sojourn in the forest. 
 This procedure involves some risk, and it is by no means 
 exceptional for the merchant to find himself in the awkward 
 predicament of having lost his capital expenditure owing to 
 the decamping of the members of the expedition to sell 
 the product of their labour elsewhere. In the Guianas 
 more favourable conditions prevail as the result of stable 
 government. In Dutch Guiana the collection is regulated, 
 a contractor paying a small sum for a permit, and hiring 
 natives, who sell all the balata they gather at a fixed sum 
 to the contractor. The undertaking has many risks, success 
 depending a good deal upon the weather, as if it is too dry 
 the water courses by which access is gained to the trees 
 cannot be navigated by the canoes. The trees in both 
 Dutch and British Guiana may reach as high as 120 feet, 
 and the rational method of tapping the trunk is generally 
 adopted. The coagulation is effected by exposing the latex 
 to the sun’s rays in shallow pans made of tinplate or of 
 wood lined with leaves. This gives the sheet balata, while 
 the Venezuelan method of boiling the latex in large kettles 
 until it is of a doughy consistency gives the block balata. 
 Both forms are familiar in the European market, the sheet 
 being the purer of the two and commanding a slightly 
 higher price. The wood of the balata tree is of a deep red 
 colour, and its hardness has caused it to he in regular 
 demand for building purposes. A good deal has been felled 
 for timber in Trinidad, and the proposal was made some 
 years ago to extract the balata from the bark by volatile 
 
BALATA. 
 
 285 
 
 solvents. There are obvious difficulties in the way of doing 
 this in such regions, hut the idea has been revived in 
 Venezuela in recent years, though with what success the 
 author is unable to state. The yield of balata is stated by 
 Clouth to be four pounds of dry substance from a gallon of 
 the latex. Raw balata varies in colour from grey to brown, 
 being sometimes red, this tint being doubtless derived from 
 the colouring matter of the wood and bark. In the sheet 
 form it is almost free from impurities of fibrous nature, 
 though the block always contains small pieces of bark. 
 Water is always present to a varying extent, also resinous 
 bodies, which may on an average be put at 40 per cent. 
 These resins differ a good deal from those of gutta percha, 
 being less crystalline and of a lower melting point, and 
 there seems little doubt that it is to them that balata owes 
 some of its specific advantages over gutta-percha. The 
 balata hydrocarbon has been recently investigated by 
 Dr. W. A. Caspari, 1 who finds it identical with pure gutta¬ 
 percha, so that there can be little doubt that it is to the 
 fact of its associated resins being of a different nature that 
 balata possesses properties not met with in gutta-percha. 
 
 Balata is soluable in the same solvents as already mentioned 
 for india-rubber and gutta-percha, but, like the latter, the 
 solution is slow unless heat is applied. Its specific gravity 
 is given as 1'05. Compared with gutta percha, it is much 
 more resistent to atmospheric oxidation, and this in addition 
 to its greater toughness, make it much superior to gutta¬ 
 percha for driving-belts. For this manufacture no special 
 machinery is required. The washing process is carried out 
 with ordinary rubber washing rolls, the loss where the 
 1 Jour. Soc. Chem. Ind. 1905. 
 
286 
 
 INDIA-RUBBER. 
 
 balata has been bought dry rarely exceeding 1 or 2 per 
 cent, on sheet balata. The amount of water, it may be 
 mentioned, is very variable, a point which should not 
 escape the attention of those who may have contracted on 
 the inspection of a dry sample. This remark applies 
 especially to block balata, of which there are several 
 qualities on the market. The base of the balata belting, as 
 in the case of the rubber belt, is a strong canvas, this being 
 passed through a solution of balata in naphtha, and when 
 the solvent has evaporated, as many plies as are required 
 are placed above one another by means of a special form of 
 calender, the whole being sewn together with two longitu¬ 
 dinal seams. Subsequent pressure forces the balata into 
 the interstices of the canvas to produce a belt which is 
 quite rigid at ordinary temperatures. According to a 
 patent taken out by Banham some ten years ago, the 
 belting was immersed in balata or gutta-percha solution 
 in a strong iron vessel connected with a vacuum pump, the 
 object being to get a better saturation of the canvas than 
 can occur under atmospheric pressure. No vulcanization 
 process is used for balata belting, and the cost of production 
 is therefore small. From the properties of the substance 
 it will be understood that these belts are not suitable for 
 very warm climates, but for moderate temperatures in 
 either dry or moist air they give general satisfaction, very 
 rarely requiring to be “ taken up.” Balata belting has 
 been made by the Gutta-percha Waaren und Treibriemen 
 Fabrik of Altona 72 inches wide, and the manufacturing 
 plant permits of 750 foot lengths being produced. It is to 
 the numerous beet sugar factories in the country that so 
 much of the German production of balata belting goes, 
 
BALATA. 287 
 
 this form of belting having been found the most suitable to 
 withstand the chemical solutions met with. It may be 
 mentioned that the present activity in the balata belting 
 manufacture is due to the lapse three years ago of the 
 Dick patent. 
 
BIBLIOGRAPHY. 
 
 The following publications are recommended to those desirous of 
 gaining further details on subjects referred to in the text:— 
 
 India-rubber, Gutta-percha, and Balata. By Franz Clouth, Cologne. 
 English trans. 1903. 
 
 India-rubber and Gutta-percha. Seeligmann Torrilhon and Fal- 
 connet. English trans. 1903. 
 
 Le Caoutchouc et la Gutta-percha. E. Chapel. 1892 (in French). 
 Chemistry of India-rubber. 0. O. Weber. 1902. 
 
 Rubber and Compounding Ingredients. II. C. Pearson. 1S99. 
 India-rubber, Gutta-percha, and Balata. W. T. Brannt. 1900. 
 Encyclopedic Roret “ Caoutchouc.” M. Maigne. 1880. 
 
 Personal Narrative of the Origin and Progress of the India-rubber 
 Manufacture. T. Hancock. 1857. 
 
 Thorpe’s Dictionary of Applied Chemistry. 
 
 Para Rubber. W. H. Johnson. 1904. 
 
 Para Rubber. Herbert Wright. 1906. 
 
 Les Plantes Tropicales de Grande Culture. M. E. De Wildeman. 
 Les Landolphiees du Senegal, etc. Ilua and Chevalier. 1901. 
 
 Die Kautschuk Pflanzen und ihre Ivultur. Dr. O. Warburg. 1900. 
 
 The following are the periodicals concerned with Rubber and the 
 Rubber trade:— 
 
 The India-rubber World, New York. 
 
 The India-rubber Journal , London. 
 
 Der Gummi Zeitung, Dresden. 
 
 Le Caoutchouc et la Gutta-percha, Paris. 
 
 Industrie et Commerce du Caoutchouc, Brussels. 
 
 The Kew Bulletin, London. 
 
 Journal of the Society of Chemical Industry, London. 
 
 I.R. 
 
 U 
 
INDEX. 
 
 A. 
 
 Acid in reclaimed rubber, 122 
 in sulphur, 146 
 Acidising process, 93 
 Admiralty specifications, 254, 263 
 Almeidzina, 45 
 Ammonia, 88, 217 
 
 carbonate, 71, 198,201 
 Analyses, guayule, 56 
 
 raw rubber, 45 
 rubber latices, 23, 24, 
 30 
 
 Antimony pentasulphide, 139,165 
 Aruwimi rubber, 41 
 Asbestos, 140, 193, 194 
 Assam rubber, 42, 63 
 Assare scrap, 34 
 
 B. 
 
 Bahia rubber, 35 
 
 Balata, 168,193, and Chap. XXIY. 
 
 Balloons, 166 
 
 Balls, 198 
 
 Barytes. 140 
 
 Belting, 194 
 
 Benguela rubber, 62 
 
 Benin rubber, 39 
 
 Benzene, 150 
 
 Benzine, 150 
 
 Birley, 2 
 
 Bisulphide of carbon, 11, 87, 167 
 Blacks, 142 
 
 Blown oils, 111 
 Bolivian rubber, 34 
 Borneo rubber, 43 
 Bornesite, 44 
 Bosanga juice, 27 
 Bottle rings, 204 
 Bronze colours, 219 
 Buffers, 188, 267 
 
 C. 
 
 Calamine, 148 
 Calender, 181 
 Cameta rubber, 33, 244 
 Card clothing, 155, 168 
 Caucho, 34 
 
 Ceara rubber, 36, 53, 54, 99 
 Chicle gum, 47 
 Clouth, F., 22, 62, 130, 164 
 Collier tyre, 236 
 Colouring matters, 138 
 Columbian rubber, 35 
 Conakry niggers, 39 
 Congo rubber, 41, 47 
 Corks, 209 
 
 D. 
 
 Dead Borneo. See Pontianak. 
 Defects in goods, 266—269 
 ! Dental rubber, 203 
 Dermatine, 114 
 
 Desulphurising, 91, 92, 121, 174 
 i Diatrine, 248 
 
 u 2 
 
292 
 
 INDEX. 
 
 Diving dresses, 228. 
 
 Doughty vulcanizing process, 89 
 Dress preservers, 168 
 Dry and moist heat test, 263 
 Dunlop Tyre Company, 89, 234 
 
 E. 
 
 Ebonite. See Vulcanite. 
 
 Eccles Rubber Company, 199 
 Electric cables, 243—246. 
 Electrical driving, 10 
 
 ,, properties of rubber, 80 
 Entrefine rubber, 24, 83 
 Equateur rubber, 41 
 Erasing rubber, 202 
 
 E. 
 
 Farina, 217 
 
 Fibre - extracting from waste 
 rubber, 119 
 Fire hose, 186 
 Flooring, 196 
 French chalk, 140 
 Friction calender, 185 
 Frue vanner, 195 
 
 G. 
 
 Gambia rubber, 38 
 Gloves, 206 
 Gold Coast rubber, 39 
 Golf balls, 175, 278, 282 
 Goodyear, 82, 249 
 Graphite, 145 
 Guayaquil rubber, 36 
 Guayule, 55 
 Gubbins, 118, 124 
 
 H. 
 
 Hancock, T., 4, 65, 82, 160, 171, 
 239 
 
 Hard rubber. See Vulcanite. 
 
 Hartridge tyre, 229 
 
 Heel pads, 192, 269 
 
 Hollander, 127 
 
 Honduras rubber, 37 
 
 Hose, 118, 182 
 
 Hot water bottles, 210 
 
 Hygiene in the factory, 11, 88 
 
 I. 
 
 Iddon’s safety clutch, 130 
 India-rubber, 
 
 action of acids upon, 72 
 ,, alkalies upon, 71 
 
 ,, copper, 78, 245 
 
 ,, grease, 77 
 
 ,, light, 75 
 
 ,, oxygen, 78 
 
 chemical composition, 65 
 deodorization, 205 
 destructive distillation, 68 
 elasticity, 67 
 
 influence of temperature, 67 
 insoluble constituent of, 64, 
 158 
 
 loss on washing, 62 
 mastication of, 5, 163 
 permeability by water, 65 
 specific gravity, 64 
 heat, 69 
 solution of, 66 
 Ink erasing rubber, 145 
 Iron oxide, 144 
 Island rubber, 32 
 Ivory Coast, 28 
 
 J. 
 
 Jamaica rubber, 57 
 Jar rings, 205—207 
 Java rubber, 43 
 Jebe rubber, 19 
 Jelutong, 46 
 
INDEX. 
 
 293 
 
 Iv. 
 
 Kassai rubber, 26, 62 
 Kerckhove, 26 
 
 L. 
 
 Lagos rubber, 30, 40, 50 
 Lamp black, 142, 241 
 Lead sulphate, 143 
 Leyland and Birmingham Rubber 
 Co., 10, 130, 161 
 Liberian rubber, 40 
 Lime, 141 
 Litharge, 143, 242 
 Lithopone, 144 
 Lopori rubber, 41 
 
 M. 
 
 Macintosh, C., 2 
 Macintosh & Co., 2, 5, 171 
 Madagascar rubber, 41 
 Magnesia, 140, 234 
 Magnesium carbonate, 140 
 Majunga rubber, 41 
 Mangabeira rubber, 34 
 Manitoba rubber, 54 
 Massai rubber, 38 
 Matto Grosso rubber, 33 
 Mats, 196 
 Mechanicals, 177 
 Mexican rubber, 38, 103 
 Michelin, 233 
 Mongalla rubber, 41 
 Motor tyres, 9, 233 
 
 N. 
 
 Naphtha, 2, 11,66, 150, 153, 158, 
 173, 213 
 
 Negroheads, 25, 33 
 New Caledonia rubber, 44 
 New Guinea rubber, 44 
 Nicaragua rubber, 37 
 
 Niger rubber, 40 
 
 North British Rubber Co., 231, 
 239 
 
 Northern Rubber Co., 216 
 North Western Rubber Co., 120 
 Noumea rubber, 44 
 
 0 . 
 
 Obach, 276 
 Okonite, 114 
 
 Oxidation of rubber goods, 73, 74, 
 269 
 
 Oxygen content of rubber, 65 
 Ozokerite, 80 
 
 P. 
 
 Packing, 192 
 Panama rubber, 37 
 Para rubber, 33, 95, 99, 161, 258- 
 Paraffin wax, 176, 232 
 Parkers’ process, 87 
 Pavement, 195 
 Pearson, 37, 145, 149 
 Penang rubber, 43 
 Penther’s patent, 119 
 Pernambuco rubber, 34 
 Peruvian rubber, 33 
 Petroleum spirit, 66, 150, 153 
 oil, 77, 120 
 Pirelli, 10, 253 
 Polish, 218, 250 
 Pontianak, 46 
 Printed textures, 219 
 Prussian blue, 209 
 Pyridine, 124, 151 
 
 R, 
 
 Rainproofs, 222 
 Rangoon rubber, 42 
 Red lead, 143 
 
 Resins of rubber, 60, 62, 73 
 
294 
 
 INDEX. 
 
 S. 
 
 Sernamby, 25, 83 
 Shale spirit, 66, 150, 153 
 Shellac, 93, 173 
 Sierra Leone rubber, 38 
 Silica, 145 
 Sincolor, 88 
 
 Specific gravity of chemicals, 138 
 Sponge rubber, 201 
 Statistics of rubber, 63 
 
 gutta-percha, 280 
 Substitute for gutta-percha, 279 
 Sulphur, 82, 145 
 
 chloride, 87, 217 
 Sulphuring up, 92 
 Surgicals, 161, 201 
 
 T. 
 
 Textile fabrics, Chaps. XIV., 
 XVI. 
 
 Thimbles, 27 
 Tobacco pouches, 165 
 Toluene, 150, 274 
 Toys, 208 
 Tuno gum, 47 
 Turpentine, 66 
 Tyndall, 68 
 
 U. 
 
 Uelle rubber, 41 
 Umbrella rings, 207 
 Up-river Para, 33 
 Upper Congo rubber, 41 
 
 V. 
 
 Vacuum drying, 133 
 Valves, 177, 189 
 Vapour curing process, 88 
 Venetian red, 144 
 Vermilion, 138, 162, 203 
 Virgin rubber, 33 
 Viscose, 113 
 
 Vulcanite, Chap. XX. and 191 
 220 
 
 Vulcanized fibre, 114 
 
 W. 
 
 Waddington’s stove, 217 
 War Office contracts, 259 
 
 solution, 158, 265 
 Warne & Co., 165, 172 
 Weber C. O., 65, 74, 84, 101, 113. 
 269 
 
 West Indian rubber, 37, 57 
 White lead, 143 
 Whiting, 147 
 
 X. 
 
 Xylene, 150 
 
 Y. 
 
 Yellow colours, 139 
 sulphur, 147 
 
 Z. 
 
 Zinc oxide, 147, 201, 263 
 sulphide, 149 
 Zingler, 114 
 
 BRADBURY, AGNEW, & CO. LD., PRINTERS, LONDON AND TONBRIDGE. 
 
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 Electric Power on Canals. Electric Traction. The Overhead 
 System and Track Work. The Conduit System. The Surface 
 Contact System. Car Building and Equipment. Electric Rail¬ 
 ways. Glossary. Index. 
 
 Decorative Glass Processes. By Arthur Louis 
 Duthie. 279 Pages. 38 Illustrations. 
 
 Contents : Introduction. Various Kinds of Glass in Use : Their 
 Characteristics, Comparative Price, etc. Leaded Lights. Stained 
 Glass. Embossed Glass. Brilliant Cutting and Bevelling. Sand- 
 Blast and Crystalline Glass. Gilding. Silvering and Mosaic. 
 Proprietary Processes. Patents. Glossary. 
 
 ( 3 ) 
 
THE " WESTMINSTER ” SERIES _ 
 
 Town Gas and its Uses for the Production of 
 Light, Heat, and Motive Power. By W. H. Y. 
 
 Webber, C.E. 282 Pages. With 71 Illustrations. 
 
 List of Contents : The Nature and Properties of Town Gas. The 
 History and Manufacture of Town Gas. The Bye-Products of 
 Coal Gas Manufacture. Gas Lights and Lighting. Practical 
 Gas Lighting. The Cost of Gas Lighting. Heating and Warm¬ 
 ing by Gas. Cooking by Gas. The Healthfulness and Safety 
 of Gas in all its uses. Town Gas for Power Generation, including 
 Private Electricity Supply. The Legal Relations of Gas Sup¬ 
 pliers, Consumers, and the Public. Index. 
 
 Electro-Metallurgy. By J. B. C. Kershaw, F.I.C. 
 318 Pages. With 61 Illustrations. 
 
 Contents : Introduction and Historical Survey. Aluminium. 
 Production. Details of Processes and Works. Costs. Utiliza¬ 
 tion. Future of the Metal. Bullion and Gold. Silver Refining 
 Process. Gold Refining Processes. Gold Extraction Processes. 
 Calcium Carbide and Acetylene Gas. The Carbide Furnace and 
 Process. Production. Utilization. Carborundum. Details of 
 Manufacture. Properties and Uses. Copper. Copper Refin¬ 
 ing. Descriptions of Refineries. Costs. Properties and Utiliza¬ 
 tion. The Elmore and similar Processes. Electrolytic Extrac¬ 
 tion Processes. Electro-Metallurgical Concentration Processes. 
 Ferro-alloys. Descriptions of Works. Utilization. Glass and 
 Quartz Glass. Graphite. Details of Process. Utilization. Iron 
 and Steel. Descriptions of Furnaces and Processes. Yields and 
 Costs. Comparative Costs. Lead. The Salom Process. The Betts 
 Refining Process. The Betts Reduction Process. White Lead Pro¬ 
 cesses. Miscellaneous Products. Calcium. Carbon Bisulphide. 
 Carbon Tetra-Chloride. Diamantine. Magnesium. Phosphorus. 
 Silicon and its Compounds. Nickel. Wet Processes. Dry 
 Processes. Sodium. Descriptions of Cells and Processes. Tin. 
 Alkaline Processes for Tin Stripping. Acid Processes for Tin 
 Stripping. Salt Processes for Tin Stripping. Zinc. Wet Pro¬ 
 cesses. Dry Processes. Electro-Thermal Processes. Electro- 
 Galvanizing. Glossary. Name Index. 
 
 Radio-Telegraphy. By C. C. F. Monckton, M.I.E.E. 
 389 Pages. With 173 Diagrams and Illustrations. 
 
 Contents : Preface. Electric Phenomena. Electric Vibrations. 
 Electro-Magnetic Waves. Modified Hertz Waves used in Radio- 
 Telegraphy. Apparatus used for Charging the Oscillator. The 
 Electric Oscillator : Methods of Arrangement, Practical Details. 
 The Receiver : Methods of Arrangement, The Detecting Ap¬ 
 paratus, and other details. Measurements in Radio-Telegraphy. 
 The Experimental Station at Elmers End : Lodge-Muirhead 
 System. Radio - Telegraph Station at Nauen : Telefunken 
 System. Station at Lyngby : Poulsen System. The Lodge- 
 
 ( 4 ) 
 
THE “WESTMINSTER” SERIES 
 
 Muirhead System, the Marconi System, Telefunken System, and 
 Poulsen System. Portable Stations. Radio-Telephony. Ap¬ 
 pendices : The Morse Alphabet. Electrical Units used in this 
 Book. International Control of Radio-Telegraphy. Index. 
 
 India-Rubber and its Manufacture, with Chapters 
 on Gutta-Percha and Balata. By H. L. Terry, 
 F.I.C., Assoc.Inst.M.M. 303 Pages. With Illustrations. 
 
 List of Contents : Preface. Introduction : Historical and 
 General. Raw Rubber. Botanical Origin. Tapping the Trees. 
 Coagulation. Principal Raw Rubbers of Commerce. Pseudo- 
 Rubbers. Congo Rubber. General Considerations. Chemical 
 and Physical Properties. Vulcanization. India-rubber Planta¬ 
 tions. India-rubber Substitutes. Reclaimed Rubber. Washing 
 and Drying of Raw Rubber. Compounding of Rubber. Rubber 
 Solvents and their Recovery. Rubber Solution. Fine Cut Sheet 
 and Articles made therefrom. Elastic Thread. Mechanical 
 Rubber Goods. Sundry Rubber Articles. India-rubber Proofed 
 Textures. Tyres. India-rubber Boots and Shoes. Rubber for 
 Insulated Wires. Vulcanite Contracts for India-rubber Goods. 
 The Testing of Rubber Goods. Gutta-Percha. Balata. Biblio¬ 
 graphy. Index. 
 
 The Railway Locomotive. What It Is, and Why It is 
 
 What It Is. By Vaughan Pendred, M.Inst.M.E., 
 Mem.Inst.M.I. 321 Pages. 94 Illustrations. 
 
 Contents : The Locomotive Engine as a Vehicle —Frames. Bogies. 
 The Action of the Bogie. Centre of Gravity. Wheels. Wheel 
 and Rail. Adhesion. Propulsion. Counter-Balancing. The Loco¬ 
 motive as a Steam Generator —The Boiler. The Construction of the 
 Boiler. Stay Bolts. The Fire-Box. The Design of Boilers. 
 Combustion. Fuel. The Front End. The Blast Pipe. Steam 
 Water. Priming. The Quality of Steam. Superheating. Boiler 
 Fittings. The Injector. The Locomotive as a Steam Engine — 
 Cylinders and Valves. Friction. Valve Gear. Expansion. The 
 Stephenson Link Motion. Walschaert’s and Joy’s Gears. Slide 
 Valves. Compounding. Piston Valves. The Indicator. Ten¬ 
 ders. Tank Engines. Lubrication. Brakes. The Running Shed. 
 The Work of the Locomotive. 
 
 Glass Manufacture. By Walter Rosenhain, Superin¬ 
 tendent of the Department of Metallurgy in the National 
 Physical Laboratory, late Scientific Adviser in the Glass 
 Works of Messrs. Chance Bros. & Co. 280 Pages. With 
 Illustrations. 
 
 Contents: Preface. Definitions. Physical and Chemical Qualities, 
 Mechanical, Thermal, and Electrical Properties. Transparency 
 
 ( 5 ) 
 
THE “ WESTMINSTER ” SERIES 
 
 and Colour. Raw materials of manufacture. Crucibles and 
 Furnaces for Fusion. Process of Fusion. Processes used in 
 Working of Glass. Bottle. Blown and Pressed. Rolled or 
 Plate. Sheet and Crown. Coloured. Optical Glass : Nature 
 and Properties, Manufacture. Miscellaneous Products. Ap¬ 
 pendix. Bibliography of Glass Manufacture. Index 
 
 Precious Stones. By W. Goodchild, M.B., B.Ch. 319 
 Pages. With 42 Illustrations. With a Chapter on 
 Artificial Stones. By Robert Dykes. 
 
 List of Contents : Introductory and Historical. Genesis of 
 Precious Stones. Physical Properties. The Cutting and Polish' 
 ing of Gems. Imitation Gems and the Artificial Production of 
 Precious Stones. The Diamond. Fluor Spar and the Forms of 
 Silica. Corundum, including Ruby and Sapphire. Spinel and 
 Chrysoberyl. The Carbonates and the Felspars. The Pyroxene 
 and Amphibole Groups. Beryl, Cordierite, Lapis Lazuli and the 
 Garnets. Olivine, Topaz, Tourmaline and other Silicates. Phos¬ 
 phates, Sulphates, and Carbon Compounds. 
 
 INTRODUCTION TO THE 
 
 Chemistry and Physics of Building Materials. 
 
 By Alan E. Munby, M.A. 365 Pages. Illustrated. 
 
 Contents : Elementary Science : Natural Laws and Scientific In¬ 
 vestigations. Measurement and the Properties of Matter. Air 
 and Combustion. Nature and Measurement of Heat and Its 
 Effects on Materials. Chemical Signs and Calculations. Water 
 and Its Impurities. Sulphur and the Nature of Acids and Bases. 
 Coal and Its Products. Outlines of Geology. Building Materials : 
 The Constituents of Stones, Clays and Cementing Materials. Clas¬ 
 sification, Examination and Testing of Stones, Brick and Other 
 Clays. Kiln Reactions and the Properties of Burnt Clays. Plasters 
 and Limes. Cements. Theories upon the Setting of Plasters and 
 Hydraulic Materials. Artificial Stone. Oxychloride Cement. 
 Asphaite. General Properties of Metals. Iron and Steel. Other 
 Metals and Alloys. Timber. Paints: Oils, Thinners and Varnishes; 
 Bases, Pigments and Driers. 
 
 Patents, Designs and Trade Marks : The Law 
 and Commercial Usage. By Kenneth R. Swan, 
 B.A. (Oxon.), of the Inner Temple, Barrister-at-Law. 
 402 Pages. 
 
 Contents : Table of Cases Cited —Part I.—Betters Patent. Intro¬ 
 duction. General. Historical. I., II., III. Invention, Novelty, 
 ( 6 ) 
 
THE “WESTMINSTER” SERIES 
 
 Subject Matter, and Utility the Essentials of Patentable Invention. 
 IV. Specification. V. Construction of Specification. VI. Who 
 May Apply for a Patent. VII. Application and Grant. VIII. 
 Opposition. IX. Patent Rights. Legal Value. Commercial 
 Value. X. Amendment. XI. Infringement of Patent. XII. 
 Action for Infringement. XIII. Action to Restrain Threats. 
 XIV. Negotiation of Patents by Sale and Licence. XV. Limita¬ 
 tions on Patent Right. XVI. Revocation. XVII. Prolonga¬ 
 tion. XVIII. Miscellaneous. XIX. Foreign Patents. XX. 
 Foreign Patent Laws : United States of America. Germany. 
 France. Table of Cost, etc., of Foreign Patents. Appendix A.— 
 i. Table of Forms and Fees. 2. Cost of Obtaining a British 
 Patent. 3. Convention Countries. Part II.—Copyright in 
 Design. Introduction. I. Registrable Designs. II. Registra¬ 
 tion. III. Marking. IV. Infringement. Appendix B.—1. 
 Table of Forms and Fees. 2. Classification of Goods. Part 
 III. — Trade Marks. Introduction. I. Meaning of Trade Mark. 
 II. Qualification for Registration. III. Restrictions on Regis¬ 
 tration. IV. Registration. V. Effect of Registration. VI. 
 Miscellaneous. Appendix C. —Table of Forms and Fees. Indices. 
 1. Patents. 2. Designs. 3. Trade Marks. 
 
 The Book: Its History and Development. By 
 
 Cyril Davenport, V.D., F.S.A. 266 Pages. With 
 7 Plates and 126 Figures in the text. 
 
 List of Contents : Early Records. Rolls, Books and Book 
 bindings. Paper. Printing. Illustrations. Miscellanea. 
 Leathers. The Ornamentation of Leather Bookbindings without 
 Gold. The Ornamentation of Leather Bookbindings with Gold. 
 Bibliography. Index. 
 
 The Manufacture of Paper. By R. W. Sindall, F.C.S., 
 Consulting Chemist to the Wood Pulp and Paper Trades ; 
 Lecturer on Paper-making for the Hertfordshire County 
 Council, the Bucks County Council, the Printing and 
 Stationery Trades at Exeter Hall (1903-4), the Institute 
 of Printers ; Technical Adviser to the Government of 
 India, 1905. 275 Pages. 58 Illustrations. 
 
 Contents : Preface. List of Illustrations. Historical Notice. Cel¬ 
 lulose and Paper-making Fibres. The Manufacture of Paper from 
 Rags, Esparto and Straw. Wood Pulp and Wood Pulp Papers. 
 Brown Papers and Boards. Special kinds of Paper. Chemicals 
 used in Paper-making. The Process of “ Beating.” The Dye¬ 
 ing and Colouring of Paper Pulp. Paper Mill Machinery. The 
 Deterioration of Paper. Bibliography. Index. 
 
 ( 7 ) 
 
THE “ WESTMINSTER ” SERIES 
 
 Wood Pulp and its Applications. By C. F. Cross, 
 B.Sc., F.I.C., E. J. Bevan, F.I.C., and R. W. Sindall, 
 F.C.S. 266 pages. 36 Illustrations. 
 
 Contents : The Structural Elements of Wood. Cellulose as a 
 Chemical. Sources of Supply. Mechanical Wood Pulp. Chemical 
 Wood Pulp. The Bleaching of Wood Pulp. News and Printings. 
 Wood Pulp Boards. Utilisation of Wood Waste. Testing of 
 Wood Pulp for Moisture. Wood Pulp and the Textile Industries. 
 Bibliography. Index. 
 
 Photography: its Principles and Applications. 
 
 By Alfred Watkins, F.R.P.S. 342 pages. 98 Illus¬ 
 trations. 
 
 Contents : First Principles. Lenses. Exposure Influences. Prac¬ 
 tical Exposure. Development Influences. Practical Develop¬ 
 ment. Cameras and Dark Room. Orthochromatic Photography. 
 Printing Processes. Hand Camera Work. Enlarging and Slide 
 Making. Colour Photography. General Applications. Record 
 Applications, Science Applications. Plate Speed Testing. Pro¬ 
 cess Work. Addenda. Index. 
 
 ^ IN PREPARATION. 
 
 Commercial Paints and Painting. By A. S. Jenn¬ 
 ings, Hon. Consulting Examiner, City and Guilds of 
 London Institute. 
 
 Brewing and Distilling. By James Grant, F.S.C. 
 
•*