\' ■:%■ ' « -f < ' .# .^^^ 1 8 ^ % * s o ' ^^' ■^0 . v 'c- '1 <~- «, -z<-*' 0' <. ^ * /■ cv "/ .•-^'^ ^ ■> ^- . -■ ,^^ -^c. ■' ■?*■ K7V, ' -f; ' . k ■*' \'\ ^'vV c ° '^ -^ « J.V -^^ '^ •■ « .\^ '' '^. >. .o<=^ >4. '°,. * » %^^* ■"^y^ V^ -/ 0" ^^ ->^:::^^^*. \/*;:^ FUR DYEING AND FUR DRESSING PEINCIPLES AND PRACTICE OF FUE DKESSING AND FUR DYEING BY WILLIAM E. AUSTIN, B.S. CONSULTING CHEMIST TO THE FUR INDUSTRY ILLUSTRATED \^^'i .-^. NEW YORK D. VAN NOSTRAND COMPANY Eight Warren Street 1922 \o'* Copyright, 1922, by D. VAN NOSTRAND COMPANY All rights reserved, including that of translation into foreign languages, including the Scandinavian . n i i^^' RUG 12 22 PRINTED IN THE UNITED STATES OF AMERICA ©CI.A677834 PREFACE THE great increase in the use of furs during the past few decades has caused the fur dressing and dye- ing industry to rise from relative insignificance to considerable importance as a branch of applied chemistry. The past eight years, moreover, have witnessed the virtual transference of the leadership in the dressing and dyeing of furs from Europe to America, and in the quality and variety of products, the domestic industry is now in every way the equal of, and in many respects superior to the foreign. The great bulk of American furs which formerly were sent to Leipzig, Paris or London to be dressed and dyed, are now being dressed and dyed in this country. In spite of these facts, very little is generally known about the nature and manner of the work constituting the dress- ing and dyeing of furs. Even among members of other branches of the fur trade, there is very little accurate in- formation on the subject. Real knowledge concerning fur dressing and dyeing is possessed only by those actually en- gaged in the industry. The interest and efforts of scientists and technologists have been enlisted to only a small extent in the technical development of the industry. The reason for this may be attributed to two related causes: first, the almost monastic seclusion in which fur dressers and dyers, particularly the latter, conducted their operations, and even to-day the heavy cloud of mystery is being dispelled but very slowly; and second, as a consequence of the first, the lack of any reliable literature on the subject. Of the few books which have been written on the industry of fur dress- ing and fur dyeing (all of them either German or French), most are hopelessly out of date, or contain no trustworthy data; or, if they do have real merit, they cannot be obtained. iii PREFACE Numerous articles in the technical journals are of interest, but they contain very little information of value. This work is intended for a two-fold purpose: first, that it may serve as a text-book for those who expect to make fur dressing and dyeing their vocation. The fundamental principles upon which the industry is based are discussed in the light of the most recent chemical and technical develop- ments, and the most important operations are treated fully and systematically, and are illustrated with practical examples. Secondly, as a practical handbook for the worker in the fur dressing and dyeing plant. The latest factory processes and methods are described, and numerous working formulas given. The formulas are all such as have been successfully used on a large scale, and give satisfactory results when applied under the proper conditions. In addition, it is believed that the book will prove of interest to chemists and other students of industrial chemis- try, since it will be an introduction into a field of applied chemistry, about which very little is known to those out- side of the industry. Thanks are due to Dr. L. A. Hausman, of Cornell Univer- sity, for material used in Chapter II; to Dr. E. Lesser of the American Dyewood Company, for information and assistance on the subject of Vegetable Dyes ; to the Gaskill Chemical Corp., American Aniline Products, Inc., the Cassella Company, and the Franklin Import := 5 z . a > •- -?^ S s § be used as the source of heat. Figure 10 shows diagram- matically the arrangement and operation of the conveyor type of dryer. The enclosure is divided into several com- 74 DRYING AND FINISHING partments, in each of which a different condition of tem- perature and humidity is maintained, the temperature be- ing closely and accurately regulated by an automatic control, and once the dryer has been set for any condition, all skins will be dried exactly the same, regardless of weather or season. 75 FUR DRESSING AND FUR DYEING The skins to be dried are placed on poles which in turn are set on the horizontal conveyors as in Fig. 11. As the skins pass through the compartments, large volumes of air, heated to the required temperature over the steam coils, are cir- culated among the skins by means of the fans. Exhaust fans, properly placed, remove a certain quantity of mois- ture-laden air when it has accomplished its full measure of work. When the skins on the conveyors have passed the full length of the dryer, they are entirely dry, and are then removed from the poles. (Fig. 12). The time required for drying varies according to the nature of the fur from 1-2 hours to 6-8 hours. In tests made to determine the relative efficiency of the conveyor type of dryer as against the old " loft " method, it was found that there was a saving of over 50% in power, and of 85% in floor space, as well as a great saving of labor, when the conveyor system was used, the number of skins dried in a given period of time be- ing the same in both cases. The advantages of the new method are easily apparent, and the saving is sufficiently great with large lots of furs, to make an appreciable differ- ence in the final cost of dressing. If the skins have been dried by a modern drying system they all come out in a uniform condition, and are ready to go on immediately to the next operation. If, however, a form of the " loft " method of drying has been used, it is customary to subject the skins to an additional process. The dried pelts are put in drums with damp sawdust, and drummed for a short time in order to get them into the proper condition. The drumming is essential for the pur- pose of equalizing the condition of the pelts, some being drier than others, and as a consequence of the contact with the moist sawdust, they are all brought to the same degree of dryness. As a result of this operation also, the skins be- come considerably softened. Then if the pelts have not been previously oiled during the tanning process, or prior to the drying, they receive this 76 DRYING AND FINISHING treatment now. The oil or fat is applied to the leather side of the furs, which are then placed in the tramping machine for a short time in order to cause the oil to be forced into the skin. The fibres of the corium thus become coated with a thin layer of fatty material, which contributes greatly to 77 FUR DRESSING AND FUR DYEING the softness and flexibility of the pelt, and increases its resistance to the action of water, and also, in certain in- stances a partial chamois tan is produced, thereby improv- ing the quality of the leather. The skins are now returned to the work bench, and sub- jected to the stretching or " staking " process. This con- sists in drawing the skin in all direc- tions over the edge of a dull blade, which is usually fixed upright in a post with the edge up. Or, the stretching may be done on the fleshing bench, substituting a dull blade for the fleshing knife. Re- cently staking machines are being used in the larger establishments, the work being done much more quickly and efficiently. As a result of this operation, the leather be- comes very soft and flexible, every bit of hardness and stiffness being eliminated, and the skins receive their maximum stretch, thereby giv- ing the greatest possible surface to the pelage. This not only helps to bring out the beauty of the hair, but is also a decided advantage from the Fig. 13. Stretching economic point of view, as a con- Machine for Cased Skins giderable Saving of material is effect- (Reliable Machine Worlcs, i • ^i • j.- ^4-^ Evergreen, L. I.) ^^^ "^ ^^^^^ ^^3"' sometmies even to the extent of twenty-five per cent. Cased skins are stretched in a somewhat different manner, by means of stretching irons. These consist of two long iron rods joined by a pivot at one end. The skins are slipped on to the irons, which are then spread apart, and in this way the skins are stretched and softened. A machine which does this work very efficiently is shown in Fig. 13. 78 DRYING AND FINISHING The skin is drawn onto the stretching arms, in this case made of bronze, which are then forced apart by pressing on a pedal. When properly stretched to the maximum width in all directions possible, and thus thoroughly softened, the Fig. 14. Fur Beating Machine. (S. M. Jacoby Co., New York.) skin can easily be reversed, that is, turned hair-side out. As many as 6000 skins can be stretched, or 4000 to 5000 skins stretched and reversed by one man in one day on such a machine. The pelts are then combed and beaten. In smaller plants these operations are done by hand, but suitable 79 FUR DRESSING AND FUR DYEING machines are being employed. In order to straighten out the hair, it is combed or brushed. Then in order to loosen up the hair, and to cause it to display its fullness, the furs are beaten. This process is also done by hand in some establishments, but up-to-date places use mechanical de- vices for this purpose. A type of machine which has proven very successful, and is enjoying considerable popularity is shown in Fig. 14. These machines are also made with special suction attachments which remove all dust as it comes out of the beaten skin, thereby making this formerly unhealthful operation thoroughly sanitary and hygienic. The final process is drum-cleaning. This operation is intended specifically for the benefit of the hair part of the fur, and is very important inasmuch as the attractive ap- pearance of the fur depends largely upon it. The drum, such as is shown in Fig. 15 is generally made of wood, or sometimes of wood covered with galvanized iron. The skins together with fine hardwood sawdust are tumbled for 2 to 4 hours, or sometimes longer. Occasionally a little asbestos or soapstone is added to the sawdust; for white, or very light- colored skins, gypsum or white sand is used, either alone, or in admixture with the sawdust; and for darker skins, graphite or fine charcoal is sometimes added in small quan- tities. The drum-cleaning process polishes the hair, giving it its full gloss and lustre, and at the same time absorbing any oil or other undesirable matter which may be adhering to the hair as a result of the washing and tanning processes. Any soap, or traces of mordant are wiped off and so re- moved, and by using heated sawdust, or heating the drum while rotating, the fur acquires a fullness and play of the hair which are great desiderata in furs. The sawdust must then be shaken out of the furs. This is done by cageing. In some instances, the drum itself can be converted into a cage, by replacing the solid door with one made of a wire screen. (Fig. 16.) Usually, however, the skins are removed from the drum and put in a separate cage, which is built 80 DRYING AND FINISHING like the drum, but has a wire net all around it, through which the sawdust falls, while the skins are held back. The cages are generally enclosed in compartments in order to prevent the sawdust from flying about and forming a dust which would be injurious to the health of the workers. Fig. 15. Drum. (Combination Drum and Cage as a Drum) {F. Blattner, Brooklyn, New York.) In large establishments, the drum-cleaning machinery occu- pies a large section of the plant, many drums and cages being used, and special arrangements being made to take care of the sawdust which can be used over again several times, until it becomes quite dirty. With this operation ends the ordinary procedure of fur dressing. But there are several additional processes re- quired in the treatment of certain furs, which are generally 81 FUR DRESSING AND FUR DYEING undertaken by the dresser, and chief among these are shear- ing and unhairing. Sometimes this work is done in separate establishments organized solely for this business. Certain Fig. 16. Cage. (Combination Dri^m and Cage as a Cage.) (F. Blattner, Brooklyn, New York.) kinds of furs, among them being seal, beaver and nutria, possess top-hair which may detract from the beauty of the fur. the true attractiveness being in the fur-hair. The top-hairs are therefore removed, and for this purpose machines are now being used. Formerly this work was all done by hand, and on the more expensive furs like seal and beaver, unhairing is now done on a machine operated by hand. The principle of the process is as follows: The skins are placed on a platform and the hair blown apart by 82 DRYING AND FINISHING means of a bellows. The stiff top-hairs remain standing up, and sharp knives are brought down mechanically to the de- sired depth, and the hair is cut off at that point. The skin Fig. 17. Unhairing M.\chine. (Seneca Machine & Tool Co., Inc., Brooklyn, N. Y.) is then moved forward a short distance, and the process re- peated until all the top-hairs have thus been cut out. With muskrats, or other pelts which do not require such very careful attention, the whole process is done automatically on a machine. The fur-hair is brushed apart by means of brushes and a comb, and at regular intervals, sharp knives cut off the top-hairs. Several hundred skins can be un- haired in a day on such a machine requiring the atten- tion of only one man. A machine for unhairing skins is shown in Fig. 17. With other furs, such as rabbits, hares, etc., where the trouble of unhairing would be too great commensurate with 83 FUR DRESSING AND FUR DYEING its advantages, the hair is sheared instead. The top hair is cut down to the same length as the under-hair by means of Fig. 18. Fur-Shearing Machine. (Seneca Machine & Tool Co., Inc., Brooklyn, N. Y.) shearing machines which can be regulated to cut to any de- sired length of hair. A typical device for shearing furs is shown in Fig. 18. 84 CHAPTER VII WATER IN FUR DRESSING AND DYEING THE assertion has often been made, although its absurdity is now quite generally realized, that the success of the European fur dressers and dyers, particularly in Leipzig, is due to the peculiar nature of the water used, which is supposed to be especially suited for their needs. The achievements in this country in the fur dressing and dyeing industry during the past few years are ample and sufficient answers to the claim of foreign superiority in this field no matter what reason maybe given, and particularly when the quality of the water used is ad- vanced as a leading argument. For the water employed by the establishments in and about New York, as well as in other sections of the country is surely not the same as the water of Leipzig, yet the work done here is in every re- spect the equal of, if not better than the foreign products. It is interesting to note that similar rumors were cur- rent here in the early period of the development of the American coal-tar industry since 1914. Our efforts to estab- lish an independent dyestuff industry were doomed to fail- ure, according to those who circulated the stories, because we did not have the water, which they claimed was respon- sible for the German success. The present status of the American dye business, in its capacity satisfactorily to supply most of the needs of this country and of others as well, speaks for itself. However, as is often the case with such erroneous asser- tions, there is just enough of an element of truth in the statement regarding the peculiar qualities of certain kinds of water, to make the matter worthy of consideration. 85 FUR DRESSING AND FUR DYEING Water is certainly a factor of great importance in fur dressing and dyeing, and it is not every sort of water that is suitable for use. This fact was recognized by the early masters of the art. for they invariably used rain-water as the medium for their tanning and dyeing materials, and their choice must be regarded as an exceedingly wise one. While the necessity for giving consideration to the quality of the water for fur dressing purposes is great, it is in fur dyeing that the effects of using the wrong water are largely evident, and so extra care must be exercised in the selection of water for this purpose. The essential requirements for a water suitable for the needs of the fur dressing and dyeing industry, are: first, a sufficient, constant and uniform supply; and second, the ab- sence of certain deleterious ingredients. Chemically pure water is simply the product of the combination of two parts by volume of hydrogen with one part by volume of oxygen. Such water can only be made in the laboratory, and is of no importance in industry. For practical purposes, dis- tilled water may be regarded as the standard of pure water. Here, too, the cost and trouble involved in the production of distilled water on a large scale is warranted only in a certain few industrial operations. A natural source of water which in its character most nearly approaches dis- tilled water is rain. In fact, rain-water is a distilled water, for the sun's heat vaporizes the water from the surface of the earth forming clouds, which on cooling, are condensed and come down as rain. Rain-water is usually regarded as the purest form of natural water. Exclusive of the first rain after a dry period, rain-water is quite free of impuri- ties, except possibly for a small percentage of dissolved at- mospheric gases, which are practically harmless, and which can usually be readily eliminated by heating the water. Moreover, rain-water is quite uniform in its composition throughout the year in the same locality, and it possesses all the desirable qualities of a water suited for fur dressing and 86 WATER IN DRESSING AND DYEING dyeing purposes. Formerly when the quantity of water used in the industry was comparatively small, the supply from rain was sufficient to meet all the requirements. But now, when tremendous quantities of water are used con- stantly, rain-water is no longer a feasible source, and other supplies must be utilized, although in a sense, all water may be traced to rain-water as its origin. When rain-water falls on the earth it either sinks into the ground until it reaches an impervious layer, where it collects as a subterranean pool, forming a well, or continues to flow underground until it finally emerges at the surface as a spring; or on the other hand the rain-water may sink but a short distance below the surface, draining off as ponds, lakes or rivers. In the first case the water is called ground water, in the latter it is known as surface water. Ground water usually contains metallic salts in solution, and relatively little suspended matter. If the water has percolated through igneous rocks, like granite, it may be quite free even of dissolved salts, and such water is considered " soft." If, however, the rocky formations over which, or through which, the water has passed contain lime- stone or sandstone, or the like, salts of calcium and mag- nesium will be dissolved by the water. The presence of the lime and magnesia salts, as well as salts of aluminum and iron, in the water, causes it to be what is termed " hard." Surface water is more likely to contain suspended matter, with very little of dissolved substances. Suspended matter, like mud, contains much objectionable matter such as putrefactive organisms and iron, but most of these materi- als can be removed by filtration or sedimentation, and sel- dom cause any difficulties. Hardness in water is generally the chief source of trouble when the water is at fault. Hardness may be of two kinds, either permanent, or temporary, or sometimes both are found together. Water which is permanently hard usually contains the lime and magnesia combined as sulphates. 87 FUR DRESSING AND FUR DYEING Temporary hardness, on the other hand, is due to the pres- ence of hme and magnesia in the form of bicarbonates, the carbon dioxide contained in the water having dissolved the practically insoluble carbonates: CaCOa + CO. + H,0 = Ca(HC03)2 calcium carbon water calcium carbonate dioxide bicarbonate Temporary hardness can be eliminated by heating the water, the carbon dioxide being expelled and the carbonates of lime and magnesia being precipitated and then filtered off. Both permanently and temporarily hard waters can be softened by the addition of the proper chemical, such as an alkaline carbonate like sodium carbonate. This precipi- tates insoluble carbonates of the lime, magnesia, iron and aluminum, leaving a harmless salt of sodium in solution in the water. The sludge is allowed to settle in tanks before the water is used. In fur dressing and dyeing, water is employed for soaking and washing the skins, dissolving chemicals, extracts and dye materials, and also for steam boilers. A small amount of hardness in the water is not harmful, and up to 10 parts of solid matter per 100,000, may be disregarded. Perma- nent harchiess is particularly objectionable in water for boiler purposes, as it forms scale. The effect of the impuri- ties of the water depends on the nature of the chemicals and dyes used. Where acids are used in solution compounds of magnesium, lime and aluminum will generally not interfere. Hard water must not be used for soap solutions, as sticky insoluble precipitates are formed with the soap by the metals, this compound adhering to the hair, and being diffi- cult to remove, will cause considerable trouble in subsequent dyeing. An appreciable loss of soap also results, as one part of lime, calculated as carbonate will render useless twelve parts of soap. In tanning or mordanting, where salts of tin, aluminum or iron are employed, hard water should not be 88 WATER IN DRESSING AND DYEING used, as lime and magnesia will form precipitates with them. Bichromates will be reduced to neutral salts, and cream of tartar will also be neutralized. With dyes also, hard water has a deleterious effect. Basic dyes are precipi- tated by this kind of water, rendering part of the dye use- less, and also causing uneven and streaky dyeings. Some- times the shades of the dyeings are modified or unfavorably affected. Considerable quantities of lime and magnesia in the water will cause duller shades with logwood and fustic dyeings. The presence of iron, even in very slight quanti- ties generally alters the shade, darkening and dulling the color. These facts were apparently all recognized and under- stood by the fur dressers and dyers of an earlier period, for instead of utilizing the water of lakes and streams near at hand, which afforded a more constant supply, but which contained harmful impurities, they collected the rain-water, which was always soft. Whether they realized the nature and character of the substances that make water hard is uncertain, but they were always careful to avoid such water. At the present time establishments located in and about large cities like New York, where the majority of American fur dressing and dyeing plants are situated, have no trouble about the water. The cities supply water which is soft, suitable alike for drinking and industrial purposes. Other plants, not so fortunately situated, often have to employ chemical means to treat the water so as to make it suitable for use. 89 CHAPTER VIII FUR DYEING Introductory and Historical IN discussing fur dyeing, the question naturally arises, " Why dye furs at all? Are not furs most attractive in their natural colors, and therefore more desirable than those which acquire their color through the artifices of man?" The answer cannot be given simply. Natural furs of the more valuable kinds are indeed above comparison with the majority of dyed furs. Yet there are several rea- sons which fully justify and explain the need for fur dyeing, for at the present time, this branch of the fur industry is almost as important and indispensable as the dressing of furs. The first application of dyeing to furs, had for its pur- pose the improvement of skins which were poor or faulty in color; or rather, the object was to hide such defects. As nearly as can be ascertained, this practise was instituted at some time during or before the fourteenth century, for fur dyeing seems to have been common during that period^ as is apparent from the verses of a well-known German satirist, Sebastian Brant, who lived in the latter part of the fourteenth century: " Man kann jetzt alles Pelzwerk fiirben, Und tut es auf das schlechste gerben." However, at a later period, there was a general condemna- tion of the dyeing of furs, and among the list of members of the furrier's guilds, none can be found who are described 90 FUR DYEING — INTRODUCTORY as dyers. There is a record of a decree issued by a prince in a German city in the sixteenth century, prohibiting the practise of fur dyeing. Inasmuch as furs were worn only by the nobility and certain other privileged classes, and also were very costly, there was great profit to be had by dyeing inferior skins so as to disguise the poor color, and then selling such furs at the price of superior quality skins. This was undoubtedly the reason for the prohibitory de- cree, but there were some who continued to practise the forbidden art in secret, using secluded and out-of-the-way places for their workshops, and mixing their carefully- guarded recipes with as much mystery as the witches did their magic potions. These circumstances probably ac- count for the great amount of mystery which has been, and still is to a considerable degree, attached to fur dyeing, and also explains the opprobrium and distrust with which fur dyers were formerly regarded. Even at the present time, dyeing is often employed to improve furs which are faulty in color. It frequently hap- pens, that in a lot of skins there are some which are con- siderably off shade, or in which the color is such as to ap- preciably reduce their value below the average, the hair being usually too light a shade, or of uneven coloring. By carefully dyeing these skins of inferior color, they can be made to match very closely the best colored skins of the par- ticular lot of furs, and consequently increase their value. With most of the cheaper kinds of furs, the trouble and cost of improvement by dyeing would not be worth while today; but with some of the more valuable furs, and especially such as are very highly prized, like the Russian sable, or marten, or chinchilla, the darkening of light skins by the skillful application of fast dyes to the extreme tips of the hair, will increase their value sufficiently to warrant the ex- pense. This dyeing or ^' blending " as it is called in such cases, is done in such a clever and artistic manner that only experts can distinguish them from the natural. Dyeing 91 FUR DRESSING AND FUR DYEING used for such purposes is not objectionable, provided the skins are sold as dyed or " blended." There are certain kinds of furs, such as the various lambs, Persian, Astrachan, Caracul, etc., which are never used in their natural color, because it is usually of a rusty brownish- black. These are furs possessing valuable qualities other- wise, so they are dyed a pretty shade of black, which brings out the beauty of the fur to the fullest extent. Sealskins are also dyed always. Formerly they were dyed a deep, rich dark brown, resembling the finest shades of the natural color, but now the seals are dyed black with a brownish undertone, a color quite different from the natural. While these two instances cannot be said to be cases of dyeing to disguise faulty color, they are examples of improvement of color by dyeing. Closely associated with the use of dyes to increase the value of a fur by improving its color, is the dyeing of skins of a certain lot of furs to produce a uniform shade, thereby facilitating or to a considerable degree eliminating the task of matching the skins by the furrier. This is usually done only on skins which are quite small, of which a great many are needed in the manufacture of fur garments, because the matching of several hundred skins would entail too much time and labor commensurate wdth the value of the fur. The most notable instance of the use of dyes to pro- duce a uniform shade on furs is the case of the moleskin. Occasionally, furs are dyed after being made into garments, by careful application of dyes, in order to obtain certain harmonious effects, such as uniformity of stripe, or to pro- duce a desired gradation of shade among the different skins comprising the garment. Not infrequently, the great variety of shades and color schemes which Nature provides in the different furs, be- comes insufficient to satisfy the desire of the fur-wearing public for something new. The whims of fashion always require some novel effect, even though it be for only one 92 FUR DYEING — INTRODUCTORY season. To meet this demand for novelty, fantasy or mode shades are produced on suitable furs, — colors which do not imitate those of any animal at all, but which, neverthe- less, strike the popular fancy. It often happens that such a color becomes quite popular, and enjoys a considerable vogue, to the great profit of those who introduced the par- ticular color effect. The best ones, however, meet with only a comparatively short-lived demand, being soon super- seded by different color novelties. The basis, though, of the greatest proportion of fur dye- ing at the present time, is the imitation of the more valu- able furs on cheaper or inferior skins. With the gradual popularization of furs as wearing apparel since the begin- ning of the last century, the demand for furs of all kinds has increased enormously. The supply of furs, on the other hand, and especially of the rarer kinds, has had difficulty in keeping pace with the requirements, and as a result there is a shortage. A very effective means of relieving this short- age, to a great degree, at any rate, is the dyeing of imita- tations of the scarcer furs on cheaper skins. There are many animals among the more common, and more easily obtainable ones, whose skins are admirably suited as the basis of imitations of the more costly furs. Some of the furs which are adapted for purposes of dyeing imitations are marmot, red fox, rabbit, hare, muskrat, squirrel, opos- sum, raccoon, and many others, and the imitations made are those of mink, sable, marten, skunk, seal, chinchilla, etc., and indeed, there are very few valuable furs, which have not been dyed in imitation on cheaper pelts. On ac- count of the general mystery which formerly surrounded fur dyeing establishments, and which has persisted to this day, although to a lesser degree, many peculiar notions were held, even by those in the fur trade, concerning the production of imitations. The idea that in order to "make" a certain fur out of a cheaper skin, it was neces- sary to use the blood of the animal imitated, is typical of 93 FUR DRESSING AND FUR DYEING the conceptions of fur dyeing held not so long ago. To-day, while the knowledge generally possessed about this branch of the fur industry is meagre and vague, the air of mystery and secrecy has become somewhat clarified, and such ideas as are current about fur dyeing are more rational than formerly. The dyeing of imitations is quite an artistic kind of work, and indeed fur dyeing ought to be classed among the finest of industrial arts. Some of the reproductions achieved by dyers on a commercial scale are truly admirable. The possibility of imitating the finer furs on cheaper skins naturally led to abuse, the dyed furs being passed off fre- quently on the unsuspecting and uninformed buyer as the genuine original. In fact, this practise became so flagrant that in England laws were enacted to remedy the evil. At the present time, dyed furs are all sold as such, although there always may be some unscrupulous merchants who seek to profit by deception. Some of the imitations and the names of the furs for which they were sold, are as follows: Muskrat, dyed and plucked sold as seal Nutria, plucked and dyed sold as seal Nutria, plucked and natural sold as beaver Rabbit, sheared and dyed sold as seal or electric seal Otter, plucked and dyed sold as seal IVIarmot, dyed sold as mink or sable Fitch, dyed sold as sable Rabbit, dyed sold as sable Rabbit, dyed and sheared sold as beaver IVIuskrat, dyed sold as mink or sable Hare, dyed sold as sable, fox, or lynx Wallaby, dyed sold as skunk White rabbit, natural sold as ermine White rabbit, dyed sold as chinchilla White hare, dyed or natural sold as foxes, etc. Goat, dyed sold as bear, leopard, etc. 94 FUR DYEING — INTRODUCTORY This list serves to indicate but a few of the great number of possibiUties which are available for the fur dyer to pro- duce imitations of the better classes of furs. Needless to say, these imitations cannot, as a general rule, equal the originals, because while the color is one of the most im- portant features in judging the fur, the nature of the hair, gloss, waviness, thickness, and also the durability are es- sential considerations, and it is only in certain instances that skins used for imitations approach the originals in these respects. However, for the purposes and desires of the majority of people who wear furs, the imitations are deemed quite satisfactory, and they also have the ad- vantage of being cheaper than the natural originals. For whichever reason furs are dyed, there is no doubt that the art of fur dyeing is one of the most difficult kinds of application of dye materials. In the dyeing of the vari- ous textiles, either as skein or woven fabric, the material is of a uniform nature, and therefore the dye is absorbed evenly by the fibres. Moreover, textiles are dyed at, or near the boil, the dyestuff being more uniformly and perma- nently taken up from solution by the fibre at elevated temperatures. How different is the case with furs! Far from being homogeneous, furs present the greatest possible diversity of fibres to be dyed. As already noted elsewhere, fur con- sists of two principal parts, the hair and the leather, differing widely in their actions toward dyes. As a general rule, the leather absorbs dyestuffs much more readily than the pelage, and inasmuch as fur dyeing is intended mainly and primarily to apply to the hair, there is usually an appreci- able loss of dye material due to its being absorbed by the leather, and thereby rendered unavailable for dyeing the hair. This fact must be taken into account in the dyeing of furs, and the methods must be adapted accordingly. With reference to the hair itself, not only has each class of furs hair of a different kind, but even in the same group 95 FUR DRESSING AND FUR DYEING there is always a considerable divergence in the properties of the hair. The fur-hair, being more or less of a woolly nature, takes up the dye with comparative ease, while the top-hair is quite resistant to the action of all dye materials. As pointed out in the discussion of the nature of fur, on different parts of the same pelt the hair varies in its capa- city for absorbing coloring matters. The color of the hair, also frequently presents a great variety throughout the skin, both in fur-hair and top-hair. Yet with all this lack of uniformity and homogeneity, the dyed fur must be of an even color, closely approaching the natural, gently graded and without any harsh or unduly contrasted effects. The natural gloss of the hair, one of the most valuable qualities of the fur, must be preserved. This is by no means a simple matter, for the luster is affected by dyes and chemicals with comparative ease, and especially careful treatment is neces- sary to prevent any diminution of the gloss. When the leather part of the fur is exposed to solutions of a temperature exceeding 40°-50° centigrade, it soon shrivels up or shrinks, and on drying the pelt, becomes hard and brittle, and therefore quite useless. Methods of fur dyeing have to take into consideration this fact, and the temperature of the dyebath must not be greater than 35°- 40° centigrade. To be sure, certain dressings make furs capable of withstanding much higher temperatures, but their applicability is not universal, being suited only for a very limited special class of dyestuffs. (V. Fur Dressing). The necessity for employing comparatively low temperatures, coupled with the great resistance of the hair to the absorption of dye, even at much higher temperatures, makes fur-dyeing a very difficult opera- tion indeed. Another obstacle which must be sur- mounted, is the possibility of extraction by the dye solution, of those materials, chemical or otherwise, which are contained in the leather, and which are the basis of its permanence, softness and flexibility. For in the majority 96 FUR DYEING — INTRODUCTORY of dressing processes, the action of the ingredients is a pre- servative one, and when these are wholly or partially re- moved from the leather during the dyeing, it becomes, on drying, hard and horny, like the original undressed pelt. In cases where furs are to be dyed, special dye-resisting dressings must be used, or the dyed skins must receive an additional dressing before drying. Dyeings on furs, to have any value, must possess great fastness to light, rubbing and wear, and must not change color in time, either when the furs are stored, or when made up into garments. The necessity for fur dyeings to have these properties, together with the difficulties outlined above, has greatly limited the field of available dyeing materials, as well as the methods of application. These will now be taken up in detail. 97 CHAPTER IX FUR DYEING General Methods BEFORE the furs can be dyed, they have to undergo certain preparatory processes: first, killing, which renders the hair more susceptible to the absorption of the dye; and second, mordanting, which consists in treat- ing the killed fur with chemicals which help the dye to be fixed on the hair. Then the skins are ready to be dyed. There are two principal methods by which dyes are ap- plied to furs in practise: the brush process, whereby only the tips or the upper part of the hair are colored; and the dip process, whereby the entire fur, including the leather is dyed. All other procedures in fur dyeing are modifica- tions or combinations of these two. Killing solutions and mordanting solutions are also applied by one of these methods, usually the dip process, although very fre- quently combinations of the brush and dip methods are used. Chronologically the brush method of dyeing came first. The early masters of the art were extremely fearful about employing any means by which there was a possibility of the leather being in any way affected. They naturally had to devise such methods as would give the desired effect in a satisfactory manner, and as would be confined solely to the hair part of the fur, leaving the leather untouched. By applying the dye or other material to be used, in the form of a paste with a brush, the upper portion of the hair only was treated. For different kinds of furs different sorts of brushes were used, and the depth to which the hair was 98 GENERAL METHODS colored could be controlled by skillful manipulation of the brushes. It was frequently necessary to give a ground color to the hair, the lower part being dyed a different shade from the tips. This was accomplished by spreading the dye paste over the hair with a broad brush, and then beating the color in with a specially adapted beating brush. With larger furs, two skins were placed hair to hair after the dye had been brushed on, and the color forced to the bottom of the hair by a workman tramping on the skins. The dye- ing of seal was a typical illustration of these procedures. First the tips of the hair were dyed. The color was brushed on, allowed to dry, then the excess beaten out with rods. These operations were repeated until the proper depth of shade was obtained, often as many as a dozen or more applications of the dye being necessary. Then the base color was spread over the hair, and beaten or tramped in until the lower parts of the hair were penetrated. This process also required drying and beating out of the excess dye, as well as numerous applications of the dye to impart the desired color to the hair. Prior to the dyeing, the furs were killed, by brushing on a paste containing the essential ingredients, drying and beating and brushing the fur, just the same as in dyeing. It will be readily seen that such methods were exceedingly laborious, and in some cases the dyeing took many weeks, and even months. It was quite a step forward when a certain fur dyer, pos- sessing a little more courage, or perhaps, experimenting spirit than the others, attempted to dye furs by dipping them entirely into a bath containing a solution of the dye instead of applying a paste as formerly. The advantages to be gained by such a method of dyeing were many. A large number of skins could be treated thus at one time, and this was a very important consideration in view of the great increase in the demand for dyed furs. By allowing the furs to remain in the dye solution until the proper shade was obtained, the time and labor of applying many coats of 99 FUR DRESSING AND FUR DYEING dye by brush was considerably reduced, and in addition, there was a greater probability of the products coming out all alike, uniformly dyed. The results as far as the hair was concerned, were indeed highly gratifying, but the con- dition of the leather after dyeing was not so encouraging. This difficulty has to a considerable degree been overcome, although there are frequent instances of the leather being affected by the dyeing process even with modern methods. However, the remedy in such cases, or rather the preventa- tive is the proper dressing of the skins prior to the dyeing. The dip method of dyeing has acquired great importance, and is being employed in dyeing operations involving the handling of millions of skins annually. In certain in- stances, nevertheless, the brush method is of prime signifi- cance as in the dyeing of seal, and seal imitations on musk- rat and coney, enormous quantities of furs being dyed in this fashion. In the majority of imitations dyed, both the brush and the dip methods must be used. Figure 19 illustrates the various types of brushes which are used at the present time for the application of the dye by the brush method. Each brush has a specific purpose and use. The procedure in brush dyeing is somewhat as follows. The skins, after being properly treated, that is, killed, and mordanted, are placed on a table, or work-bench, hair-side up. Then by means of a brush which is adapted to the nature and requirements of the particular fur, the solution is brushed on in the direction of the fall of the hair, occasionally beating gently with the brush so as to cause the dye to penetrate to the desired depth. Considerable skill and care must be exercised in this operation as it is rather easy to force the dye down further than is wanted, and in some cases the leather or the roots of the hair may be affected. The skin having received its coat of dye, is then dried and finished, if no other dyeing processes are to be applied. Frequently, with certain types of dyes, several applications of color are necessary, and these are brushed 100 GENERAL METHODS on as the first one, drying each time. Then, on the other hand, the skin may receive a dyeing in the bath by dipping, and for this also, the fur is first dried after the brush dyeing. Quite recently, owing to the great quantities of furs which are being dyed as seal imitations, chiefly by the brush method, although the dip method is used in conjunction with it, machines have been invented to replace the hand brush, and the dye is now applied mechanically. Machines ^¥^^^^|k _maoeQfiwwtfi^ Fig. 19. Brushes Used in Fur Dyeing By the Brush Method. for this purpose are by no means new, there being records of inventions almost a score of years past, but they did not achieve much success. Brush-dyeing machines, to be effi- cient, must be designed to suit the needs of the particular type of fur to be dyed, otherwise there will be a great lack of uniformity in the dyed skins, a condition which cannot occur when the dye is brushed on by hand brushes. Fig- ure 20A and B shows diagramatically, machines invented within the past few years, which are used to dye mechani- cally furs by the brush process. 101 Fig. 20. Types of Machines for Dyeing Furs By the Brush Method. A. (U. S. Patent 1,225,447.) B. (U. S. Patent 1,343,355.) 102 GENERAL METHODS For the dipping process, the dye solution is prepared in vats, or liquid-tight drums, or in some instances in paddle arrangements. The skins are placed in the dye-bath, and the dyeing operation proceeds without any difficulty. After the proper shade is obtained, the furs are removed, washed free of excess dye, dried and finished. The dipping method Fig. 21. Drum For Working With Liquids. {Turner Tanning Machinery Co., Peabody, Mass.) is employed where a single shade is to be dyed on the fur, as the production of blacks on lambs. But in most cases, the dyeing in the bath is supplemented by the application of a coat of dye by the brush to the upper part of the hair, the color being usually a darker shade than the ground dyeing. Thus, for example, in the dyeing of imitation sable on kolinsky or a similar fur, the skins are first dyed the relatively light color of the under-hair by the dip process, then the dark stripe effect is brushed on. 103 FUR DRESSING AND FUR DYEING The blending of sables, martens, chinchillas or other rare furs, is not done in the same manner as with other furs, because each skin requires individual attention and a long and careful treatment. The dye solution is applied by- means of very fine brushes or sometimes feathers, to the extreme tips of the hair, until the proper degree of color intensity is obtained. The time, labor, and skill necessary for this sort of work are warranted only in the case of the Fig. 22. Device For Conveying Skins. (^Turner Tanning Machinery Co., Peabody, Mass.) highest-priced furs, and the blendings are so excellent as to defy detection, except by experts. After the furs have gone through all the operations re- quired by the processes of killing, mordanting, dyeing and washing, they are ready to be dried and finished. The pro- cedure is quite similar to that employed in fur dressing. Sometimes the leather side of the skins is brushed with a strong salt solution before drying, in order to replace some of the salt which was extracted during the dyeing processes. In other instances, a light coat of some oily substance is 104 GENERAL METHODS brushed on, to render the leather soft and flexible after drying, where there is a possibility of the skins turning out otherwise. Great care must be exercised in the handling of the dyed skins to avoid the formation of stains or spots on the hair, which might ruin the dyeing. As little hand- ling of the furs as is feasible will reduce any trouble from this source. In conveying the wet skins from one part of the plant to another it is desirable to use a device such as is shown in Fig. 22. For drying, the same machines as described under Fur Dressing can be used, and similar care must be taken to avoid overheating or irregularity of dry- ing. Drum-cleaning constitutes a very important opera- tion in the finishing of the skins, the hair receiving a polish, and the full lustre and brilliancy of the dye being thereby brought out. Then after caging to remove the sawdust or sand, the skins are passed over the staking knife, or are treated in a machine suited for the purpose, to stretch them and to render them thoroughly soft and flexible. And therewith is concluded the work of the fur dyer proper, and the skins are ready to return to the furrier, in whose hands they undergo the metamorphosis into the fur gar- ments to be worn chiefly by the feminine portion of humanity. 105 CHAPTER X FUR DYEING " Killing " the Furs IF dressed furs are treated with a paste or solution of a dye properly prepared, and at the right temperature, the hair will show very little tendency to absorb the coloring matter. Even after prolonged treatment with the dye, only a small amount will be taken up by the hair, and in a very irregular fashion. Soft, woolly hair, like that of lambs and goats will be colored more easily than that of furs with harder hair, and the under-hair of a fur will generally have a greater affinity for the dye than the harder and stiffer top-hair. Moreover, in some parts of the same fur, the hair will absorb more color than in other parts. In other words, the hair of furs resists the action of dye materials to a greater or less degree, depending upon the character of the fur, and also upon the part of the pelt. In order to overcome this resistance of the hair, and to render it uniformly receptive to the coloring substances, the furs are treated with certain chemical agents, the process being known technically as " killing." The origin of the term is obscure, but it is interesting to note that in the fur dyeing countries other than the United States and England, the corresponding expression is used: in Germany, '' toten," and in France " tuer." The explana- tion of the process is as follows: The surface of the hair is covered with a fine coat of fatty material which renders the hair more or less impervious to dye solutions and solu- tions of other substances which may be used for dyeing purposes. This fatty coating of the hair cannot be removed 106 "KILLING" THE FURS by mechanical means, otherwise the hair would have been freed of it during the dressing operations. Chemical sol- vents must therefore be resorted to, and naturally alkaline materials are used, these being usually cheapest and also most effective in their dissolving action on fatty substances. Alcohol, ether, benzine, and other similar liquids also serve as killing agents on furs, since they too, are fat solvents. In all these cases, the fatty substance on the hair is dis- solved away, and the protective coat which previously ren- dered the hair impervious to the dye, is now removed. There are certain chemicals however, which normally do not dissolve substances of a fatty nature, but are strongly oxidizing, such as peroxide of hydrogen, hypochlorites, permanganates, perborates, nitric acid, etc., and exert a killing action when they are applied to the hair, in that the hair is made capable of taking up the dye from its solu- tions. In this case the killing can hardly be said to be due to a degreasing process. The fact that killing can be brought about with other substances than alkalies or fat solvents, has led to the belief on the part of some investi- gators in this field that killing is more than a degreasing operation, although the removal of the fatty material of the hair undoubtedly takes place. Some authorities con- sider that the killing process changes the pigment of the hair, which thereby becomes more receptive to the dye. It is quite possible that some such change in the structure of the hair fibre does take place, the surface of the hair be- coming slightly roughened, and therefore more capable of fixing the coloring matter. The question is still an open one, and since no conclusive researches have been made as yet, it will be assumed that killing is simply a degreasing process, inasmuch as the modern practise is based on this supposition, and very satisfactory results are obtained. An account of the historical development of the killing process brings out many interesting and enlightening facts, so it will be given here briefly. One of the first substances 107 FUR DRESSING AND FUR DYEING used for killing, or degreasing the hair of furs, was de- composing urine. Urine contains about 2% of urea which gradually changes to salts of ammonia, and in the presence of the air, largely to ammonium carbonate. This substance has a weak alkaline action, but sufficiently effective to be used for killing the hair of certain types of furs. Woolly furs, such as those derived from the various kinds of sheep and goats, were degreased with stale urine, the skins being washed in this, and then rinsed in water. The fat was emulsified by the ammonium carbonate present, and could thus be easily removed. For other furs, a stronger mixture was necessary. An example of a killing formula used on wolf, skunk and raccoon, which were to be dyed black, is the following : 350 grams beechwood ashes 200 grams unslaked lime 150 grams copper vitriol 100 grams litharge 60 grams salammoniac 40 grams crystallized verdigris 3.5 liters rain water Beechwood ashes were a very important constituent of the old killing formulas. The reason for that lies in the fact that beechwood contains a comparatively high percentage of potassium, which occurs in the ashes of the burned wood as potassium carbonate, or potash. The ashes alone were frequently used, being applied in the form of a paste, which in some instances had an advantage over a solution, in that the killing could be limited to certain parts of the skin where it was more desired than in other parts. By extract- ing the wood ashes with hot water, and evaporating the clear solution to dryness, potash could be obtained, which was considerably stronger than the original ashes. Next in importance for the killing was unslaked lime. This substance was also often used by itself, being first slaked 108 ''KILLING" THE FURS with water, and using the milk of lime thus formed, after cooling. Salammoniac, although a salt, and consequently without any killing action, in contact with the beech wood ashes or the lime in solution or paste, liberated ammonia slowly, and so also acted as a degreasing agent. The other chemicals in the formula took no part in the actual killing of the hair, but acted either as mordant materials or as mineral dyes. The copper salts, in this mixture present in two forms, as sulphate in copper vitriol, and as acetate in the verdigris, were important constituents of the dye for- mula, being essential to the production of the proper shade. These substances properly had no place in the killing for- mula. The litharge, also was not a killing agent, but in the presence of the alkaline materials of the killing mixture, it gradually combined with the sulphur contained in the hair, forming lead sulphide, and thereby darkening the color of the hair. In this case, the metallic compound acted, not as a mordant, but as a mineral dye. The mixture was applied to the hair by means of a brush, the skins let lie for some time, then dried, brushed and beaten. Many applications were usually necessary to sufficiently degrease the hair. Inasmuch as the killing paste was prepared by mixing the constituents together, and then was brushed on at the comparatively low temperatures which the proper protection of the hair required, it is questionable whether some of the metal compounds were even enabled to act as described above as mordant or dye. In spite of the trouble and considerable time required in working with such a killing formula to obtain the hair in the desired condition for dyeing, the use of such a mixture nevertheless possessed the advantage that the hair was only very slowly and gradually acted upon, and so the gloss was preserved. The action of strong alkaline substances acting quickly is more or less detrimental to keeping the gloss of the hair, while the slow action of the weak alkaline paste of the old formu- las, and the gradual formation of a protective metal film on 109 FUR DRESSING AND FUR DYEING the surface of the hair, rendered the hair suitably receptive to the dye which was subsequently applied, without in any measure affecting the lustre of the hair. It would be needless to describe or discuss any more of the old killing formulas, for the principle involved was the same in all cases, there being usually a slight variation in the content of metallic salts, beechwood ashes and unslaked lime being constituents of the great majority of the mix- tures used. Modern killing processes employ substances quite similar to those of the old formulas, the operations, however, being much less laborious and less time-consum- ing, and the cheap, pure products which chemical science has been able to develop being used in place of the crude products crudely obtained from natural sources. The chem- icals used at the present time for killing furs, are chiefly ammonia, soda ash, caustic soda, and caustic lime. The choice of the killing agent depends upon the nature of the fur, the hair of some furs being sufficiently killed by treatment with weak alkalies, while in other furs the hair may require stronger treatment. The ability of the hair of a particular fur to withstand the action of the different alkaline substances must be taken into consideration, there being a great divergence in this regard among the different classes of furs. Raccoon, for example, is not appreciably affected by a solution of caustic soda of 5 degrees Beaume, while some wolf hair cannot withstand the action of a solu- tion of soda ash of less than 1 degree Beaume. Frequently much stronger alkalies are necessary to kill the top- hair than the under-hair, so this accomplished by treat- ing the skins in a solution which is suited to kill the under-hair, and subsequently the top-hair is treated with a stronger solution, this being applied by the brush method. Uniformity of action of the killing material on all parts of the skin, and on all the skins of a given lot, is absolutely essential to obtaining satisfactory results in dyeing. And 110 "KILLING" THE FURS it is by no means a simple matter to get such uniformity, considering the numerous factors that must be taken into account. Any operation involving the immersion of the skins in solutions or even in water alone, has an effect on the leather side of the skin, inasmuch as some of the tan- ning materials may be extracted. The application of some substance of a fatty nature to a great degree prevents this, and the skin can be killed, mordanted and dyed, and then come out soft and flexible. But the great majority of substances of a fatty nature are affected by alkalies, and so when the skins are being killed, the action of the alkaline materials would be upon the fat contained in the leather as well as that upon the hair. As a result the hair may not be sufficiently killed, and so give uneven dyeings sub- sequently. Either a certain excess of the killing chemical must be used, and it would be very difficult to ascertain what quantity would suffice, or the killing action must be prolonged; but best of all, in oiling the skins, an inert mineral oil should be used, since it is wholly unaffected by alkalies. Skins may be killed by the brush process or the dip proc- ess, or by both. For brush killing, the stronger alkalies like lime and caustic soda are used, the solution being ap- plied to the top-hair with a suitable brush, and the skins allowed to remain hair to hair for the necessary length of time, after which they are treated further as skins killed by the dip process. By this latter process, the furs are immersed in a solution of the desired killing agent in a vat, or drum, or other appropriate device which will permit of uniform action of the alkali on the hair of all the skins. After remaining in the solution the required length of time, the skins are drained, and rinsed in fresh water, and then entered into a weak solution of an acid in order to neutralize any remaining alkali, it being easier to wash out acid than alkali. The furs are then washed thoroughly in clear water, preferably running water, to remove the last traces of acid. Ill FUR DRESSING AND FUR DYEING The skins are then drained and hydro-extracted, or pressed, and are then ready for the subsequent operations of mor- danting and dyeing. Killing with Soda Soda is sodium carbonate, which is produced commer- cially in a very pure state in several different forms, the chief being sal soda, which is crystallized sodium carbonate, containing about 37% of actual soda; and soda ash, or calcined soda, which is anhydrous sodium carbonate. The latter is the variety most commonly used. 10 grams soda ash are dissolved in 1 nter of water at 25^''-30° C. The skins are immersed for 2-3 hours, after which they are rinsed and treated with 10 grams acetic acid dissolved in 1 liter of water. The skins are again thoroughly washed, and then hydro- extracted. Killing with Lime Lime, calcium oxide, forms a white, amorphous, porous substance, which readily takes up water, giving calcium hydroxide, or slaked lime. Only the best grades of lime should be used, as it is very frequently contaminated with calcium carbonate and other inert materials. 10 grams of lime are dissolved in 1 liter of water. The skins are entered, and allowed to remain for a period of time which varies according to the nature of the fur. During the killing, the solution must be agitated, in order to evenly distribute the milk of lime, which has a tendency 112 "KILLING" THE FURS to settle out. After rinsing, the skins are " soured," by- treating with weak acetic acid solution, then thoroughly washed, and drained. Killing with Caustic Soda Caustic soda is used only on furs the hair of which is very hard and resistant to killing. LTsually it is applied by the brush process, but in some instances, the dip method must be used. In order to reduce as far as possible, the action of the caustic soda on the leather, the weakest per- missible solutions are used, increasing the time of treat- ment, if necessary. Caustic soda is a white, crystalline substance, occurring in commerce in lumps, but more con- veniently in a solution of 40 degrees Beaume, containing 35% of caustic soda. Various quantities, ranging from 4 to 25 grams of this solution per liter of water are taken, according to the character of the fur, and the skins treated for 2-3 hours, although weaker solutions may be used, and increasing the duration of the killing. By keeping the solution in motion, by means of a stirrer or any other method of agitation, the best results are obtained. After the skins are sufficiently killed, they are soured, and washed as by the other killing methods. Where the nature of the hair of the fur is such that the top-hair and the under-hair require different killing treat- ments, the skins are first killed by the dip process, with an alkali suited to kill the under-hair, then a brush killing with a stronger alkali is applied to the top-hair. The subsequent treatments are the same as for usual dip-killing methods. 113 CHAPTER XI FUR DYEING Mordants THE hair of furs has the peculiar quality of fixing the oxides or hydroxides of certain metals from dilute solutions of their salts. Advantage is taken of this property to mordant the furs, that is, to cause a cer- tain amount of the metallic oxide or hydroxide to be perma- nently absorbed by the fibres. The term mordant comes from the French word " mordre," meaning to bite, it being formerly considered that the purpose of a mordant was to at- tack the surface of the hair in such a way as to permit the dye to be more easily absorbed. In fact, killing mixtures, which were intended for this same object, used to contain the various chemicals which have a mordanting action, in addition to the alkaline constituents. The mordants were not applied as such, but always as killing materials. It was later realized, however, that the mordant was instru- mental in the production of the color itself. Mordanting may be considered as having a two-fold object: first, to help fix the dye on the fibre in a more permanent fashion, thus rendering the dyeings faster; and secondly, to help obtain certain shades of color, as the various mordants produce different shades with any given dye. Some classes of dyes can be applied to furs without the use of mordants, but other types are taken up only in a very loose manner, being easily washed out from the hair with water, and it is only when such dyes are brought on to the hair in the form of a metallic compound, pro- 114 MORDANTS ducing what is known as a '' lake," that really fast dyeings are obtained with them. The substances which are used for mordanting the hair are certain metallic compounds, but not all metallic salts which are used in dyeing are mordants. Sometimes such a compound is employed to develop the color of the dyeing by after-treatment, as in the case of after-chroming, the action of the metallic salt being directed only to the dye, and is not fixed by the fibre as a mordant must be. In order for a metallic compound to act as a true mordant, it must be fixed by the hair, and it must combine with the dye, thus forming a sort of connecting link between the dye and the hair. It is not absolutely essential that the mordant be applied first, although this is the customary and commonest practise. There are three ways by which the mordants. can be fixed on the fur hair: First, by the absorption of the metallic oxide or hydroxide from a solution of the mordant prior to the dyeing; second, the mordant may be fixed on the fibre at the same time as the dye; and third, the mordant may be applied after the fur has been treated with the dye. The last two meth- ods will be discussed in connection with the dyes, as they are special cases. The salts of metals which are comparatively easily dis- sociated in water, with the formation of insoluble oxides or hydroxides, are most applicable as mordants for furs, and among them are compounds of aluminum, iron, chro- mium, copper and tin. The constituents of the hair seem to bring about the dissociation of the metallic salt, and the oxide or hydroxide as the case may be, is absorbed and firmly fixed by the hair. Just what the manner and nature of this fixation are, is still uncertain. It is supposed that chemical combination takes place between the hair and the metal. The course of this process may, as far as is known, be described as follows, taking, for example, the case of chromium sulphate: In dilute solution, this com- pound gradually dissociates first into its basic salts, and 115 FUR DRESSING AND FUR DYEING finally into the hydroxide, the breaking up of the neutral salt being induced by the presence of the fur-hair, Cro(S04)3 + 2HoO = Cro (804)2 (OH). + H2SO4 chromium water first basic sulphuric sulphate " chrome salt acid Cr2(S04)2(OH)2 + 2H20 = Cr2(S04)(OH)4 + H2SO4 second basic chrome salt Cr2(S04)(OH)4 + 2H2O = Cr2(OH)6 + H2SO4 chromium hydroxide These reactions take place within the fibre, after the hair has been impregnated with the solution of the neutral salt, and when the compound has been rendered completely basic, in other words has reached the form of the hydroxide, it is supposed to combine with the acid groups contained in the hair substance, forming thus some complex, insoluble organic compound of the metal within the hair. Accord- ing to some authorities the mordant is supposed to be present in the hair simply as the hydroxide, being tena- ciously held by some physical means. The facts seem to indicate, however, that the metal is actually combined in some chemical way with the hair. For, if the mordant were present as hydroxide, then on white hair it would show the color of the hyth'oxide, which it does not. The same facts obtain with regard to other metals. In order for the hair to be properly mordanted, it is nec- essary that the metallic compound which is taken up by the hair be held in such a manner that the mordant cannot be removed by water or even dilute acids or alkalies. Salts which dissociate too readily produce mordants which are only superficially precipitated on the hair and subsequently come off. Usually some substance is added to the solution of the salt to cause slower and more even dissociation of the salt, so that the hair substance can be quite saturated with the metallic compound before any insoluble precipi- 116 MORDANTS tate is formed. Dilute sulphuric acid, organic acids like acetic and lactic, and cream of tartar are used to facilitate the uniform absorption of the mordant salt by the hair. When the skins are mordanted before dyeing, they are immersed for 6 to 24 hours in a solution containing 1 to 20 grams of the metallic salts per liter of water, together with the corresponding quantity of the assistant chemical. The skins should be so entered into the mordant solution that the hair is uniformly in contact with the solution, and all the skins so that they are acted upon alike. Machinery such as is used for killing is suitable for mordanting also. The duration of the mordanting, and the concentration of the solutions are varied according to the depth of shade required, and also according to the nature of the dye to be employed. By suitably combining several mordants a con- siderable range of colors can be obtained with a single dye. The various chemicals used as mordants are essentially the same no matter for which class of dyes they are used, there being only slight differences in the concentrations of the solutions, the manner of application of the mordants being practically the same. It is interesting to note that with the exception of chromium compounds, which are of comparatively recent adoption as mordants, all the chemi- cals now used for mordants were employed by the earliest masters of the art of fur dyeing. While some of the formu- las used by those dyers display a lack of appreciation of the true action and function of the mordanting chemicals, yet it is quite remarkable that they chose, in spite of their limited knowledge of chemical processes and phenomena, just those materials which do act as mordants if prop- erly applied. The most important metallic compounds for mordanting furs at the present time are salts of aluminum, iron (ferrous), copper, tin and chromium (as well as chro- mates and bichromates). The compounds of the metals with organic acids such as acetic acid are preferable, being more easily dissociated, and also leaving in solution an acid 117 FUR DRESSING AND FUR DYEING which is less injurious to the fur than a mineral acid. How- ever, sulphates and other salts of the metals are also used ex- tensively, inasmuch as they are cheaper than the organic salts. Aluminum Mordants Chief among the aluminum mordants are the various kinds of alum, which is a double sulphate of aluminum and an alkali such as sodium, potassium or ammonium. All these salts except that of sodium, form large, colorless, octahedral crystals, and are soluble in about 10 parts of cold water, and ^ part of hot water. Sodium alum is even more easily soluble, but on account of the difficulty of obtaining it in crystalline form, it is little used. The com- mon commercial alum is the potassium aluminum sulphate. Recently, aluminum sulphate has to a large extent re- placed alum for mordanting purposes, because it can be obtained very cheaply in pure form, and it contains a greater amount of active aluminum compound than does alum. Only the iron-free salt, however, may be used for the needs of fur dyeing. Aluminum acetate also finds extensive application as a mordant in fur dyeing, and while somewhat more expensive than the alum or aluminum sulphate, it has the advantage over these compounds of being combined with an organic acid, which is preferable when the action on the hair and leather is considered. Aluminum acetate can be obtained in the market in the form of a solution of 10 degrees Beaume, but can also be prepared very easily as follows : 665 grams pure aluminum sulphate, or 948 grams potassium alum, are dissolved in 1 liter of hot water. 1137 grams of lead acetate (sugar of lead) are also dissolved in 1 liter of hot water. 118 MORDANTS The two solutions are mixed, and thoroughly stirred. A heavy white precipitate forms, which is filtered off, and dis- carded after the solution has cooled. The aluminum ace- tate is contained in the filtrate, and the solution is brought to a density of 10 degrees Beaume by the addition of water, if necessary, and is preserved for use in this form. Iron Mordants Ferrous sulphate, iron vitriol, or copperas, as it is com- monly known, forms pale green crystals, which on exposure to air lose water, and crumble down to a white powder. It is very soluble in both cold and hot water, but the solutions oxidize very rapidly, turning yellowish, and should there- fore be used immediately. Care must be taken that a good quality of iron vitriol be used for the mordant, otherwise very unsatisfactory results will be obtained. Ferrous acetate is prepared in a manner similar to the aluminum acetate, and is occasionally employed instead of the ferrous sulphate. Inasmuch, however, as the solution of ferrous acetate is very easily oxidizable when exposed to the air, a more stable form is used, and this comes on the market as iron pyrolignite or iron liquor. This can be prepared by dissolving iron in crude acetic or pyroligneous acid, or by treating a solution of iron sulphate with calcium pyrolignite. Iron liquor is really a solution of ferrous ace- tate that contains certain organic impurities w^hich prevent, or rather, considerably retard the oxidation of the iron salt, but which in no way interfere with its mordanting proper- ties. The commercial product can be had in various con- centrations, but 10 degrees Beaume is the most usual and most convenient. Copper Mordants The most important copper salts used in fur dyeing processes are copper sulphate, or blue vitriol, occurring in 119 FUR DRESSING AND FUR DYEING large blue crystals, very soluble in cold and in hot water; and copper acetate, which is formed by treating a solution of copper sulphate with a solution of the requisite quantity of lead acetate. Copper acetate can also be obtained in the form of blue-green crystals, very soluble in water, the solution becoming turbid on prolonged heating, due to the formation of a greenish basic copper acetate. This insol- uble compound is known commonly as verdigris, although it is not usually produced in the manner mentioned. Nu- merous fur dyeing formulas contain verdigris, but inasmuch as the basic copper acetate is insoluble and thus incapable of reacting with any of the substances used in dyeing, it is assumed that the soluble normal copper acetate was meant, for this compound is also sometimes called verdigris. In addition, there must be mentioned here a compound which formerly found extensive use in fur dyeing. This is a double salt of copper and iron, analogous to alum, fer- rous copper sulphate, known as blue salt. It is very seldom used at the present time, being more effectively replaced by other substances. Chromium Mordants The typical chromium mordant is chrome alum, which is a potassium or ammonium chromium sulphate, constituted just like the aluminum alums, and forming crystals like these. More frequently used, nevertheless, than the chrome alum, is chromium acetate, which is prepared from it, either by treating a solution of the chrome alum with a solution of lead acetate, or in the following manner : 50 grams of chrome alum are dissolved in 500 cubic centimeters of boiling water. To this is added 15 grams of 20% ammonia, diluted with 15 grams of water. 120 MORDANTS The precipitate which forms is filtered off, and preserved, the filtrate being discarded. After thoroughly washing the residue on the filter it is dissolved in dilute acetic acid, heating if necessary, to effect solution. Other chromium compounds of an entirely different type are also used in fur dyeing, these being chromates and bichromates, the latter finding greater application than the former. Sodium bichromate is the salt most usually em- ployed. This forms orange-red crystals which are very soluble in water, and in addition to its use as a mordant it also serves as an oxidizing agent for developing or fixing certain dyes on furs. Tin Mordants Compounds of tin find only limited application in fur- dyeing, the only one of importance being tin salts, stannous chloride, which occurs in the form of white, hygroscopic crystals, which must be preserved in closed vessels. It is very soluble, but in dilute solutions it readily forms a basic salt, so stannous chloride is usually used in very concen- trated solutions. Alkaline Mordants After the furs have been treated with the solution of some alkali for the purpose of killing the hair, they are always passed through a slightly acidulated bath to re- move any alkali which may still be adhering. This opera- tion must always be gone through before the skins can be mordanted or dyed, for if it were neglected, very uneven and uncertain results would be obtained. This process, however, entails the expenditure of no small amount of time, labor and chemicals when large lots of skins are being handled. In order to eliminate this extra step of " souring " between killing and mordanting or dyeing, it has been pro- 121 FUR DRESSING AND FUR DYEING posed to use alkaline mordants which combine the killing and mordanting functions, and accomplish these two proc- esses at the same time. The advantages of employing such mordants are easily apparent. Cumbersome manip- ulation and handling of the skins, with the attendant con- sumption of much time and labor are reduced to a mini- mum, and besides there is no needless waste of chemicals as is the case in the ordinary methods of killing the furs. The principle of alkaline mordants is not a strictly new one. If it be remembered that the old killing formulas used by the fur dyers of an earlier age, contained metallic salts with mordanting properties in addition to the alkaline sub- stances, which alone were effective as killing agents, it would seem that the suggested alkaline mordants were merely a revival in modified form of the old processes. This is undoubtedly true in a large measure, for the killing mix- tures which the old masters used certainly embodied the fundamental principle of simultaneous killing and mor- danting, although it was not recognized at that time. Modern alkaline mordants have therefore been devised which can be employed for killing and mordanting furs at the same time. They are prepared as follows : Alkaline Aluminum Mordant 250 grams of potassium alum are dissolved in 1 liter of boiling water. To this solution is added 300 grams of soda ash, previously dissolved in 750 c.c. of water, and the resulting precipitate is filtered off, washed and pressed, and then dissolved in a "solution of 65 grams of caustic soda in 1 liter of water. 122 MORDANTS Alkaline Chromium Mordant 250 c.c. of chrome acetate mordant of 20 de- grees Beaume 320 c.c. of caustic soda solution of 38 degrees Beaume (32.5%) 10 c.c. of glycerine 30 degrees Beaume (95%) The solution of these substances is brought up to a volume of 1 liter by the addition of 420 c.c. of water. Alkaline Iron Mordant 138 grams ferrous sulphate are dissolved in 362 c.c. of warm water. Cool and add 25 c.c. of glycerine. Then slowly and carefully add 25.5 c.c. of concentrated ammonia, taking care that no precipitate forms. While these alkaline mordants seem to have much in their favor, there are certain possible objectionable features which must be considered. The solutions of the mordants are generally very alkaline, and not every fur can withstand more than a limited quantity of alkaline substance for longer than a comparatively short time. Suitable mordant- ing usually requires a longer time than killing does, so with the use of the alkaline mordant, if the skins remain in the solution until sufficiently killed, they may be in- sufficiently mordanted, while if the furs are treated long enough to be properly mordanted, the hair may have been over-killed. However, the idea of the alkaline mordant is a good one, and it is only a matter of time and patient, scientific experimentation when the difficulties of the method will be eliminated, and a much-desired process will become a practical realization. 123 FUR DRESSING AND FUR DYEING The general methods for applying the various mordants of all sorts follow closely the procedure adopted for the killing formulas, and similar precautions must be observed, in order to obtain consistently uniform results. With the exercise of care, there is little reason for the mordanting operations to go wrong. After proper treatment of the skins in the mordants, they are removed and drained off, then rinsed lightly in running water to remove the excess of mordant liquor, after which they can be directly entered into the dye bath. If it is not feasible to dye the mordanted skins at once, as is often the case, the skins are kept moist, and under no circumstances allowed to dry. 124 CHAPTER XII FUR DYEING Mineral Colors Used on Furs BEFORE the introduction of the fur dyes now used, certain inorganic chemical substances were em- ployed in addition to the vegetable dyes, for the production of colors on furs. Even to this day such mate- rials are used to obtain certain effects in special instances. The idea of employing mineral chemicals undoubtedly ori- ginated in the textile-dyeing industry, which at one time was dependent to an appreciable extent on mineral sub- stances for the production of certain fast shades. Com- pounds of iron, lead, manganese, also of copper, cobalt and nickel were all used for dyeing, either singly or in various combinations. In the application on furs^, the brush method was the only one practicable, as the skins would have been ruined by dipping them into solutions of these chemicals in the concentrations necessary for dyeing. The dyeing of furs with mineral colors involves the pre- cipitation on the fibre in a more or less permanent form of the sulphide, oxide or other insoluble compound of a metal, and can be brought about in several ways. By what is known as double decomposition, that is, by the use of two solutions successively applied, the ingredient of one causing a precipitate to form when in contact with the constituent of the second, the color is produced on the hair. Another method is to use solutions of chemicals which decompose on contact with the hair, forming an insoluble compound. In the first method the hair is alternately treated with the two solutions of the requisite chemicals, 125 FUR DRESSING AND FUR DYEING drying between each brushing, the process being repeated until the desired shade is obtained. The second method merely requires the solution of the chemical to be applied to the hair, which is then dried, the color forming by itself. One of the most important of the mineral dyes, and which is occasionally used to this day, is lead sulphide, formed by the double decomposition method by precipita- ting a soluble lead salt with ammonium sulphide, or any other alkaline sulphide. By simply brushing an aqueous solution of lead acetate, also known as sugar of lead, on a white fur such as white hare or rabbit, a light, brownish coloration is obtained due to the combination of the lead with the sulphur of the hair. If the lead solution is care- fully applied several times on this type of fur, until a sufficiently dark color is produced, it is possible to get a fairly good imitation of the stone marten. The brown color is very fast, being actually formed within the hair. In most cases, however, for dyeing lead sulphide shades it is necessary to use the two solutions. Thus the pale greyish or slightly brownish-grey shades of the lynx can be reproduced on white rabbit or hare by this process. A solution containing 60 grams of lead acetate per liter of water is brushed on to the hair of the fur which has pre- viously been killed in the usual manner, and the hair is then dried. A solution of 50 grams of ammonium sulphide per liter of water is next brushed on, and the fur again dried. Care must be exercised in handling the ammonium sulphide as it is a very malodorous liquid, the fumes of which are poisonous when inhaled. The alternate brush- ings are repeated until the desired depth of shade is ob- tained. A very dark brown, approaching a black can be obtained in this way. This color can be used for the production of certain attractive effects. By brushing over the tips of the hair, which has previously been dyed a dark brown by means of the lead sulphide color, with a dilute solution of hydrochloric acid, or with peroxide of 126 MINERAL COLORS USED ON FURS hydrogen, the hair will become white in the parts so treated, due to the formation of lead chloride or lead sulphate, respectively. Thus white tipped furs can be obtained, but the process is applicable only when the furs have been dyed by the lead sulphide method. Potassium permanganate is occasionally used to produce dyeings of a brown shade on furs. Considerable care has to be taken in applying this substance, as it is possible to affect the hair. The strength of the solution must be va- ried according as the hair to be dyed is weak or strong. A cold solution of 10 to 20 grams of potassium permanga- nate per liter of water is brushed on to the hair, which is then dried. A brown precipitate of manganese is formed on the hair after a short time, and the process is repeated until the required shade is obtained. For furs with harder hair, stronger solutions can be used. The dyeing is very fast, but it is seldom used, cheaper and better shades being obtained in other ways. Spotted white effects can be pro- duced on the brown dyeing with permanganate of potash by applying a solution of sodium bisulphite, the brown color being dissolved by this chemical. The compounds of other metals, such as iron, copper, cobalt and nickel are not used in practise as the dyeings are not fast, and can be better produced in other ways. 127 CHAPTER XIII FUR DYEING Vegetable Dyes WITH the exception of the few shades which could be produced solely by means of coloring matters of a chemical character, all dyeings on furs up to about thirty years ago were made with dye substances obtained from the vegetable kingdom, either alone, or in conjunction with the aforementioned mineral colors. The colors of vegetable origin used in comparatively recent times were mainly extracts of the wood of certain trees; so the name " wood dyes " has come to be applied generally to the dyes of this class. The use of the vegetable or nat- ural dyes on furs dates back to quite ancient times, as frequent allusions and descriptions in Biblical and other contemporaneous literature testify. There are numerous pictures on monuments and tablets illustrating the dyeing of furs among the ancient Egyptians, the evidence indicat- ing that the juice of certain berries, and extracts of certain leaves, were used for the purpose. At a later period, in the Roman era, henna, which was used over two thousand years ago as to-day for the beautification of the hair of women, was also used to color fur skins. The instances cited here are merely of scientific and historical interest, and are not of practical importance as far as fur dyeing methods are concerned. It was not until many centuries later that the dyeing of furs took on the aspects of a commercial art, and the sub- stances then employed were chiefly tannin-containing ma- terials such as gall-nuts and sumach, which in conduction 128 VEGETABLE DYES with certain metallic salts, particularly those of iron, were capable of producing dark shades. The use of iron com- pounds to form dark grey or black colors on leather tanned by means of the tannins, had been common for a long time, and it was natural that fur dyers should try to pro- duce such shades on furs in a similar fashion. The use of the iron-tannin compound as a dye proved to be very effective, and to this day the production of blacks by means of the vegetable coloring matters has as a basis an iron- tannate. A formula in common use in the latter seven- teenth and the eighteenth centuries for producing black shades on furs, is the following: Lime water 1117 parts Gall-nuts 1500 ' Litharge 500 ' Salammoniac 65 ' Alum 128 ' Verdigris 64 ' Antimony 64 ' Minium 32 ' Iron filings 128 ' Green copperas 384 ' All these substances except the gall-nuts, the copperas and half the lime water were boiled up in a cauldron; then the gall-nuts and the copperas were placed in a bucket and the contents of the cauldron poured in, and the rest of the lime water added. The mixture was stirred up, allowed to settle for an hour, and when cool, was ready to be applied by the brush method. For dyeing by the dip process, a similar mixture was used, only considerably diluted with water. A study of the formula discloses the fact that in it are combined killing and mordanting substances as well as dyeing materials. The lime water, in conjunction with the salammoniac serves as a killing agent, the verdigris, cop- 129 FUR DRESSING AND FUR DYEING peras and alum are mordants, while the litharge and the minium, both compounds of lead, could possibly act as mineral dyes, and the iron filings and the antimony took virtually no part at all in the dyeing, except, perhaps to act in a mechanical way. The formulas for other shades were made up along sim- ilar lines, the chief constituent of vegetable nature being either gall-nuts, sumach, or both. A mixture for a chestnut brown, for example, contained gall-nuts, sumach, and the various other mineral constituents as in the black dye, litharge, alum, copperas, verdigris, salammoniac, antimony, and in addition, red lead and white lead. It is evident in both these instances that the shade obtained was as much the result of mineral dyeing as of vegetable dyeing. The discovery of America introduced into Europe many new dye substances, chiefly wood extracts such as logwood and Brazilwood, but it was not until the nineteenth cen- tury that these materials found their way into the dye formulas of the fur dyer. Most of the processes used in the dyeing of furs were adaptations of methods employed in silk dyeing, the silk fibre being considered as most nearly approaching fur-hair in nature and characteristics. By devious and circuitous paths the formulas of the silk dyers reached the fur people, and so, in the middle of the nine- teenth century, dye mixtures containing the various dye- woods as well as the tannin-containing substances were in general use for the dyeing of furs. The following is a typical recipe of that time for the production of black on furs like wolf, skunk, raccoon, etc. : Roasted gall-nuts 1000 parts Sumach 200 " Iron mordant 200 " Copper vitriol 100 " Litharge 80 " Alum 60 " 130 VEGETABLE DYES Salammoniac 50 " Crystallized verdigris 40 " French logwood extract 30 " Rain water 7000 " The mixture was boiled up, and after cooling was ready for application by the brush method, the skins being first killed by a killing mixture also applied by the brush. The dye substances in this case are the gall-nuts, sumach and the logwood extract, with the iron mordant, copper vitriol, and alum as mordants. For brown shades a similar formula was used containing Pernambuco wood extract, logwood extract, quercitron bark, gall-nuts and dragonblood, together with iron, copper and alum mordants. Formulas such as the above were mainly empirical, that is, they were compounded as a result of trial of various combinations of the constituents, without considering the nature and quantitative character of the reactions, as long as the desired shades could be obtained. Such dye mixtures were frequently found to yield results varying from those expected or originally obtained, because the effectiveness of the formulas depended upon the exact duplication in every detail, of conditions which had given satisfactory results previously, and it was not always possible to attain such an accurate reproduction of circumstances, especially when the fur dyers were quite ignorant of the scientific relationships of the materials used. So when more light had been shed on the nature and chemical characteristics of the vegetable dye substances, formulas like those des- cribed were no longer employed, although the essential ingredients were the same in the new processes. Unneces- sary constituents were eliminated, and proper ones sub- stituted where it was required, and the quantities of the materials used were made to conform to the chemical laws governing the reactions. Since these new formulas were based on a rational understanding of the constituents and 131 FUR DRESSING AND FUR DYEING their reactions, it is desirable to study the latter briefly, before further discussing the formulas themselves. The substances of vegetable origin used in modern fur dyeing may be grouped into two classes, one, the tannin- containing materials, and the other, the dyewoods proper. The most important of the tannins are gall-nuts, sumach and chestnut extract. Cutch, which also comes under this class, is more frequently used for the production of brown shades, so it is grouped with the dyewoods. Among the latter are logwood, fustic, Brazilwood, quercitron, turmeric, and several others of less significance. 1. Tannin Materials First and foremost under this heading are the nutgalls. These are ball-shaped excrescences produced on certain plants by the punctures of insects in depositing their eggs. There are two chief varieties, the European, and the Chinese. The European galls are formed by the female gall-wasp which drops an egg in the rind of young branches of certain oaks. A swelling (the nutgall) is produced, in which the young insect develops, and from which it finally escapes by piercing a hole through the shell. Those galls which are not pierced have a fresh bluish or green color, are heavy and contain most tannic acid. After the insect has gone out, the galls are of a lighter, yellowish color, and also of inferior quality. The best oak-galls are the Aleppo, and the Turkish or Levant galls, containing 55- 60% of tannic acid, and about 4% of gallic acid. The Chinese galls are produced by the puncture of a plant- louse on the leaves and leaf-stalks of a species of sumach, and not on oaks. The galls are very light, and very rich in tannic acid, containing often as much as 80%. For dyeing purposes, nutgalls are usually ground to a powder, and in some instances they are even roasted first and then ground. 132 VEGETABLE DYES Sumach consists of the leaves and sometimes of the small twigs and stems of a species of sumach plant known as the Rhus coriaria. The Sicilian variety is the finest commercial quality, with the Virginian ranking next. It is sold as a powder, but also in the form of the whole or crushed leaves. The best sumach contains 15-25% of tannin. Extracts are also manufactured, a liquid extract of 52 degrees Twaddell, which forms a dark brown, thick paste ; and a solid extract, formed by evaporating the liquid extract to dryness. Chestnut extract is prepared from the wood of the chest- nut oak, which contains 8-10% of tannin. The solid ex- tract has a bright, black color, while the liquid extract is a dark brown paste with a smell like that of burnt sugar. The tannins all give greyish to black shades with iron salts, and it is this fact which renders them important for fur dyeing. 2. Wood dyes One of the most important of all the natural dye sub- stances, especially for the production of blacks, is logwood. The color is really a red, but with the common mordants it forms blue, violet or black shades. Logwood, or cam- peachy wood, as it is sometimes called, is the product of a large tree growing in the West Indies, and Central and South America. When freshly cut, the wood is practically with- out color, but when exposed to the air it soon becomes a dark reddish-brown on the surface. The coloring principle of logwood is called hematoxylin, which is a colorless sub- stance when pure, and is of itself incapable of dyeing; but when it is exposed to the air, especially when moist and in the presence of some alkaline substance, it is converted into hematein, which is the real coloring matter of logwood. To prepare the wood for use, the logs are chipped or rasped, the chips being heaped up and moistened with, water. Fer- mentation occurs, and the heaps are frequently turned to allow free access of air to the wood, and to prevent over- 133 FUR DRESSING AND FUR DYEING heating. As a result of this process, a great part of the hematoxyhn is converted to the hematein. The logwood may be used for dyeing in this state as chips, but logwood extracts can now be obtained of a high degree of purity and are easier to work with. The commercial forms of the extract, are the liquid of 51 degrees Twaddell, and the solid extract. Hematein crystals can also be obtained. All these extracts contain mainly hematein, together with a small percentage of hematoxylin Avhich is con- verted to the former during the dyeing process. Log- wood is never used as a direct dye, but is used to form color lakes with the various mordants, the following colors being produced: Iron mordants give grey to black shades Copper mordants give green-blue to black shades Chrome mordants give blue to black shades Aluminum mordants give violet shades Tin mordants give purple shades By combining several of the mordants, any desired shade of black can be obtained, and if other dyewoods are used in conjunction with the logwood, the range can be further increased. Fustic, yellow- wood, or Cuba wood, as it is variously called, is obtained from a tree also growing in the West Indies, Central and South America. It is used either as wood chips, or as a paste extract of 51 degrees Twaddell, and occasionally as solid extract. Fustic contains two col- oring matters, morintannic acid, possessing the character- istics of a tannin, and which is quite soluble in water, and morin, which is rather insoluble, and which settles out from the liquid extract. Fustic is the most important of the yellow dyes of natural origin, and is used considerably in fur dyeing with logwood for shading the blacks, or for producing compound shades. With the usual mordants fustic gives the following colors: 134 VEGETABLE DYES With iron salts dark olive With copper salts olive With chrome salts olive-yellow to brownish- yellow With aluminum salts . . . yellow With tin salts bright yellow to orange- yellow Brazilwood, or redwood, is the product of a tree found in Brazil, and exists in several varieties, such as peach wood, Sapan wood, Lima wood, and Pernambuco wood. They all yield similar shades with the various mordants, and all seem to contain the same coloring principle, brasilin, which, like the hematoxylin, has no dyeing power, but by fermen- tation and oxidation it is converted to brasilein, corres- ponding to the formation of hematein. Brazilwood and the related woods are used either as chips or extract, but seldom alone, usually in conjunction with other dyewoods. By combining logwood, fustic and Brazilwood in various proportions, and by employing suitable mordants, all the shades required by the fur dyer can easily be produced. Quercitron is the inner bark of a species of oak (Quercus tinctoria) found in the United States. It contains two coloring principles, quercetrin and quercetin. The fresh decoction of quercitron bark is a transparent dull orange- red which soon becomes turbid and deposits a yellow crystalline mass. It is generally used in conjunction with other dyes. Cutch is the dried extract obtained from a species of acacia, the principal varieties being Bombay, Bengal, and Gambler cutch. It contains two coloring principles, cate- chin and catechu-tannic acid. Cutch acts as a tannin, and like other tannins discussed above, can be used for the pro- duction of grey or black shades with iron mordants. It is employed chiefly, however, for dyeing browns. Aluminum salts give with cutch a yellowish-brown, tin salts give a 135 FUR DRESSING AND FUR DYEING lighter yellow, copperas gives a brownish-grey, and chrome and copper salts give brown shades. Turmeric is the underground stem of the curcuma tinc- toria, the coloring principle being called curcumin. It may be used as a direct dye, but usually a mordant is used. Turmeric is sometimes used in place of fustic. While the tannins can be used alone with an iron mor- dant for producing greyish to black shades, the dyewoods alone yield colors which would be too bright to be suitable for dyeing furs. In order to tone down this brightness, and to give to the dyeings that greyish undertone which is characteristic of the natural furs, and which can only be imitated by means of the iron-tannin compound, it is cus- tomary to combine the tannins with the wood dyes. The iron-tannate constitutes the foundation of the color which gets its intensity, and necessary brilliancy and bloom from the wood dyes. Moreover, the presence of the iron-tannin compound helps considerably to increase the fastness of the dyeing. Furs dyed with the combination of the tan- nins and the wood dyes obtain an additional tanning treat- ment which materially improves the quality of the leather, for not only do the tannin substances exert this tanning action, but the dyewoods as well, for they are themselves either of the nature of tannins, or contain a coloring prin- ciple which is a tannin. It is to the combined effects of the tannin substances and the dyewoods that furs dyed with vegetable dyes owe their beauty of color, lustre, naturalness of shade, permanence of the dyeing, and durability of the leather. Wood dyeings on furs have for this reason ac- quired a just renown, but owing to the introduction of the new kinds of fur dyes, the use of the vegetable dye sub- stances has been greatly reduced. The dyes of vegetable origin can be applied to furs by either the brush method or the dip method, or both, and since mordants are required with the dyes of this class, they are applied in one of the three ways mentioned in a 136 VEGETABLE DYES previous chapter: first, by mordanting before dyeing; sec- ond, by applying mordant and dye simutaneously ; and third, by mordanting after the skins have been treated with the dye. I. Dyeing with Vegetable Dyes by the Brush Method The use of the brush method in applying the natural dyes to furs is limited to a comparatively few kinds of dyeing, namely to produce special effects on furs, or to give to the upper-hair of furs a coat of dye different from the base color. In a quite recent German patent is described a process for blending a red fox as a silver fox and the procedure affords a good example of brush dyeing with preliminary mordanting. The specification is as follows: " D. R. P. 310, 425 (1918). A process for dyeing red fox as silver fox. The tanned and dressed skin is first super- ficially decolorized by applying a dilute mixture of milk of lime, iron vitriol and alum, with a soft brush so as only to penetrate the top-haiT. Allow to remain for 4—6 hours, dry, and beat out the dust. A dilute solution of iron vitriol is brushed on so as only to wet the top-hair, and the skin is thus allowed to remain moist for 12-24 hours. Then without drying, a solution of iron vitriol, salammoniac, litharge, red argol and wood ashes is brushed on cold with a hard brush so as to penetrate all the hair down to very near the skin. The skin has now completely lost its red color, and has become a pale yellow. It is now ready to be dyed. An infusion of roasted nutgalls, which have been boiled for 3^ hours with water, is applied cold with a soft brush to the upper hair. Allow to remain so for 2-3 hours, and without drying, apply a weaker solution of the roasted nutgalls with a hard brush so as to saturate the hair thor- oughly. Dry and beat out. According to the concentration of the solution applied, the hair will be colored blue-grey 137 FUR DRESSING AND FUR DYEING to black, and the shade can be varied by varying the strength of the solutions used. The different parts of the skin, or those parts of different shades can be dyed accord- ingly." . In this patent all the operations, including killing, mor- danting and dyeing are done by the brush method, and the process, from this point of view is quite similar to one which might have been employed a century previous. It is evident that the time and effort required to carry out the details as described in the patent would only be war- ranted in exceptional cases, where the value of the dyed fur would be considerably greater than that of the natural skin. An example of the application at the same time of dye and mordant by the brush method is the original French Seal dye, which is still employed to a limited extent to produce a brilliant, deep, lustrous black topping on furs which have already been dyed by the dip process. A typi- cal formula for the old French Seal dye is the following: Green copperas 10 parts Alum 10 " Verdigris 10 " Gall-nuts 80 " Logwood extract (15 degrees Twaddell) 150 " Water 1000 " This mixture is applied to the top of the hair of the furs, after previous killing, and the skins allowed to remain moist for several hours, and also exposed to the air. The skins are then dried, and beaten out, and if necessary a second coat of dye is brushed on. In dyeing seal-imitation on muskrat, or skunk-imitation on opossum, for example, the black color required on the top-hair, or the upper part of the hair when the furs are sheared, can be produced by applying a mixture similar to the above, to the furs 138 VEGETABLE DYES after they have received their base color by the dip process with natural dyes or with the Oxidation Colors. Occasion- ally, the dyeing is given an after-treatment with a dilute solution of sodium bichromate to help develop the color, the action in this case being that of an oxidizing agent, and not of a mordant. As far as the third method of mordanting is concerned, that of first applying the dye, and then the mordant, it is rarely practised with the brush method. The procedure, however, consists in first brushing on a solution of the de- sired dye, then drying and brushing on a mordant solution. These operations are repeated perhaps two or three times until the proper shade is obtained, exposing the furs to the air for the color to be developed. II. Dyeing with Vegetable Dyes by the Dip Method It was in the application to furs by the dip process that the use of the vegetable dyes attained great importance, and although at the present time, natural organic dyes have largely been superseded by the Oxidation Colors and Aniline Black dyes, yet for certain purposes, and especially for the production of blacks, the wood dyes still are able to hold their own. The dyeing of black formerly constituted probably the most important branch of the fur dyeing industry, and was undoubtedly the most difficult one. For it is possible to obtain as many different kinds of black as there are dyers of this color, but only a few certain shades are desir- able. The division of the classes of furs into those derived from the various kinds of sheep, and those obtained from other animals is particularly marked in the dyeing of black, and both the composition of the dye formulas and the methods of dyeing are somewhat different for the two groups. For the dyeing of black on Persian lambs, broad- 139 FUR DRESSING AND FUR DYEING tails, caraculs, etc., a combination of logwood and nut- galls with the requisite mordants is used, while on hares, Chinese sheep, foxes, raccoons, opossum, etc., a mixture of logwood and turmeric or fustic, with the proper mor- dants is used. The general procedure is as follows : The dye substances to be used are ground up to a powder in a mill constructed for the purpose, after which they are boiled with water in a copper-lined kettle or cauldron, heated from the outside by steam. The customary arrangement is to have a jack- eted kettle, supported on a stand, and having taps and valves to enable the liquor to be drawn off, or pivoted, so that the kettle can be tilted, and the contents poured out. The use of the copper-lined vessel is to be preferred, as it is unaffected by any of the dye substances, and so cannot cause any rust stains. After the dyes have gone into solu- tion and have cooled, the mordant chemicals, previously dissolved in water, are added, and the mixture stirred up. The dyeing in this instance is effected by the simultaneous application of dye and mordant. The dye mixture is now run off, or poured out in the proper quantity into a number of small vats of 25-30 gallon capacity, or into a paddle vat, which can be closed, while the paddle is rotating. The lat- ter device is to be preferred because it permits the dye to retain its temperature better and for a longer period of time, but when lambs are being dyed only the open vats are used. The temperature of the dye mixture is between 40° and 45° C, for only at this temperature can the hair absorb the dye properly without injuring the leather. The killed skins are immersed in the dyebath for a time, usually overnight, after which they are removed, drained and hung up, with the hair-side exposed to the air, so as to permit the dye to develop, which takes place with the aid of the atmopheric oxygen. The dyebath is again brought to the proper temperature, and the skins are again entered, to go through the same process as often as is necessary to obtain 140 VEGETABLE DYES the desired depth of shade. The dyed skins are thoroughly washed to remove excess dye, then dried and finished. The following are a few dye formulas used in the production of blacks : Logwood extract 100 grams Chestnut extract 14 c.c. Turmeric 38 grams Iron acetate 6° Be 50 c.c. Water 1200 c.c. or, Cutch 15 grams Soda 14 grams Logwood extract 120 grams Verdigris 19 grams Iron acetate 5° Be. 16 c.c. Water 1200 c.c. A recently published formula for dyeing China goat skins black, is the following: Dissolve 50 lbs. of dark turmeric and 45 lbs. of logwood extract and make up to 300 gallons of solution, at 95° F. Enter the killed skins and leave them in the liquor until they rise to the surface. Then take them out and add 25 lbs. of logwood extract, 10 lbs. of sumach, 10 lbs. of blue vitriol, 5 lbs. of fustic extract, and about 60 lbs. of iron acetate liquor. Stir up well, and immerse the skins for 18 hours. Draw them up, and expose to the air for 12 hours. Heat the liquor again to 95° F. and put the skins back for 12 hours. Draw out, hang up in the air for a time, then wash thoroughly, hydro-extract, dry and finish. In a German patent, D. R. P. 107,717 (1898), is de- scribed a method for dyeing lambs black, consisting in treating the skins for 24 hours in a logwood bath, then rinsing in cold water, and mordanting for 15 hours in a solution of bichromate of potash. The skins are then washed and treated with a solution of iron salt, then dried. 141 FUR DRESSING AND FUR DYEING This process, while of not much practical importance, is an illustration of mordanting subsequent to the dyeing treatment. As far as the production of other shades is concerned, the procedure is quite similar to the regular black method. For a dark brown, for example, the skins are dyed in a mixture containing Gall-nuts 40 parts Verdigris 10 " Alum 10 " Copperas 5 " Brazilwood extract (15° Twaddell) 150 " Water 1000 " employing operations just as in the case of the black. Greyish-blue shades on white hares, lambs, kids, etc., can be obtained by treating the skins successively in the follow- lowing baths: 1. Logwood extract 100 grams Water 1 liter 2. Indigotine 10 grams Alum 10 grams Water 1 liter Bluish-grey tones on the same furs can be produced by treating with 1. Logwood extract 200 grams Indigotine 15 grams Water 1 liter 2. Alum 150 grams Salammoniac 12 grams Water 1 liter 142 VEGETABLE DYES Similar grey shades can be produced by mordanting the skins with an iron salt, and then dyeing in a weak bath containing gall-nuts, sumach and iron vitriol. This method is very effective for making Alaska or silver fox imitations. 143 CHAPTER XIV FUR DYEING Aniline Black FUR seal for a long time has been a fur of distinction and importance in the fur industry, and consequently the dyeing of seal has constituted an important, though not very extensive branch of the art of fur dyeing. In quite recent times the popularity of seal has become so great that imitations have had to be produced to help supply the demand, and as a result, French seal, or seal-dyed rabbit, and the so-called Hudson seal, which is seal-dyed muskrat, have acquired a great vogue. Occasionally opos- sum, nutria and other furs are also used for the purpose of producing seal imitations. While the supply of real seals is relatively small, and the demand large, the pro- duction of seal imitations has assumed large proportions, and as a result, the dyeing of seal and its imitations or substitutes has come to be a great branch of the fur dyeing industry. During the past thirty years, the long and tedious proc- esses of dyeing seal and seal imitations, involving the use of dyes of vegetable origin, have largely been superseded by what is known as the Aniline Black dye. It was the French who first worked out successfully the application of Aniline Black to furs, and the method has attained much importance and extensive use in the fur dyeing industry. Aniline Black is the name given to an insoluble black dyestuff produced by the oxidation of aniline in an acid medium. As a finished product it cannot be used in fur dyeing, but if the hair of the furs be impregnated with a 144 ANILINE BLACK suitable preparation of aniline and then treated with cer- tain oxidizing agents, the color will be formed on the hair, being firmly fixed and giving a fast black, resistant to light, washing and rubbing. The basis of the dye, aniline, is an oily liquid, possessing a peculiar fishy odor, colorless when pure, but rapidly turning brown when exposed to the air. It is obtained from benzol, which is distilled from coal-tar, by treating with nitric acid, forming nitrobenzol, which when subjected to the action of reducing chemicals is converted into aniline. The process may be shown schematically as follows: Coal — coal-tar — benzol — nitrobenzol — aniline oil — Aniline Black. Aniline Black was by no means a new dye when the French succeeded in producing it on furs. It had been used for a long time previous on textiles, chiefly cotton. The history of the development of the Aniline Black proc- ess throws considerable light on its nature and constitu- tion, and so presents many features of interest. As early as 1834, the chemist Runge observed the formation of a dark green color when heated aniline nitrate in the pres- ence of cupric chloride. Fritsche, in 1840, noticed that when chromic acid was added to solutions of aniline salt, a dark green, and sometimes a blue-black precipitate was produced, and later the same chemist obtained a deep blue by the action of potassium chlorate on aniline salt. It is interesting to note that Perkin, in 1856, conducting simi- lar experiments on the oxidation of aniline with chromic acid, obtained a blue-black product from which he extracted the first synthetic coal-tar dye, mauve. Thus far, all the experiments on the oxidation of aniline proved to be merely of scientific interest, but in 1862, Lightfoot patented a process for the practical application of colors formed by the oxidation' of aniline on the fibre, a greenish shade being obtained by that method, to which the name emeraldine was given, and by subsequent treatment with bichromate of potash, the green was changed to a deep blue color. 145 FUR DRESSING AND FUR DYEING Since that time, the methods for producing and applying Aniline Black have been developed and improved, although all the processes were based on the principles incorporated in Lightfoot's original patent. However, it was not until the last decade of the nineteenth century that the dyeing of furs by means of the Aniline Black method was successfully attempted. A knowledge of the nature and the manner of the chem- ical changes which take place in the production of Aniline Black is a valuable aid in obtaining satisfactory results in practise; and although Aniline Black was extensively used before the true character of the reaction was under- stood, since the successful determination of the constitu- tion of Aniline Black and the discovery of the real nature of the process by Green and his collaborators in 1913, the methods have been considerably improved and simplified, with correspondingly better results in dyeing. As a conse- quence, the methods of dyeing furs with Aniline Black have also become simpler and more efficient. A discussion of the chemical changes which occur in the Aniline Black process, is out of place here on account of the highly involved and complicated character of the reac- tions, to understand which requires a considerable knowl- edge of specialized organic chemistry. But the essential features of practical importance in the production of Ani- line Black are the following: As already noted, one of the characteristic properties of aniline is its tendency to turn from a colorless to a dark-brown liquid in the pres- ence of the air. This change is due, together with certain other causes, to an oxidation brought about by atmospheric oxygen. By employing oxidizing agents, this oxidation can be accelerated and carried further, and eventually the Aniline Black is obtained. Among the substances which may be used to bring about the conversion of aniline to the insoluble black dye are manganese dioxide, lead perox- ide, hydrogen peroxide, chromic acid, ferric salts, potassium 146 ANILINE BLACK permanganate, chloric acid and chlorates in the presence of certain metallic salts, particularly those of vanadium and copper. Chlorates, especially sodium chlorate and potas- sium chlorate, are the most commonly employed oxidizing agents, bichromate of soda or of potash being used, in addition, to complete the oxidation. When using chlorates it is necessary to have present in the dye mixture a small quantity of a metallic salt, which, while not entering into the reaction itself, is nevertheless indispensable as an oxy- gen carrier. Vanadium compounds have proved to be the most effective for this purpose, and according to an author- ity, one part of vanadium salt is sufficient to cause the conversion of 270,000 parts of aniline to Aniline Black, the necessary amount of a chlorate being present of course. Salts of copper, cerium, and iron are also extensively used, but they are not quite so efficient as vanadium. The formation of the Aniline Black in practise takes place in three well-defined steps, which it is important to be able to recognize and distinguish in order to obtain the best results. The first stage of the oxidizing process produces what is called emeraldine, which in the acid medium of the aniline bath is of a dark green, while in the free state it is of a blue color. As the oxidation proceeds, the second stage develops, the emeraldine being converted to a compound called nigraniline. This in acid solution is blue, and the free base is a dark-blue, almost black. It was formerly considered that the nigraniline was the Aniline Black proper, and so when this stage of the oxidation was reached, the process was often interrupted and not carried to the limit. This can account for the fact that Aniline Black dyeings usually turned green after a short time. The reason for this is that nigraniline, when treated with weak reducing agents, as, for example, sulphurous acid, is at once changed to emeraldine, with its dark green color. Since there is usually a small amount of sulphurous acid in the air, especially in places where coal or gas is burned, an 147 FUR DRESSING AND FUR DYEING Aniline Black dyeing which has not been carried beyond the nigraniline stage will be reduced in time to the emerald- ine, and cause the dyeing to become green. The last step in the oxidation changes the nigraniline into what is prop- erly called the ungreenable Aniline Black. Weak reducing substances like sulphurous acid do not change this com- pound to emeraldine, and stronger reducing agents only convert it to a brownish compound, which changes back to the black when exposed to the air. It is quite evident that in order to obtain a black which will not change to green in time, the oxidation of the aniline must be carried to the last stage. By making tests during the dyeing of the furs, it can easily be determined whether the oxidation has proceeded far enough. In the dyeing of textiles with Aniline Black, it is custom- ary to carry out the operation at comparatively high tem- peratures, approaching 100° centigrade. With furs such temperatures are out of the question, so it is necessary to repeat the dyeing several times in order to obtain the proper depth of shade working in the cold. Only the brush method can be used in applying the Aniline Black dye to furs, on account of the strong acidity of the dye mix- ture, which would ruin the leather, if the dyeing were done in a bath. Indeed, great care must be exercised even by the brush method to avoid too great penetration of the dye liquid, otherwise the roots of the hair will be attacked, and the leather may be " burned " from the hair side. Furs dyed with Aniline Black are frequently after-dyed by the dip-process with logwood or some other similar dye, in order to add to the brilliancy of the dyeing. Combined with in- tensity of color. Aniline Black on furs is the only dye which will also give fast, lustrous shades, and leave the hair soft and smooth. There are several methods of applying Aniline Black on furs, the most important being 148 ANILINE BLACK 1. One-bath Aniline Black 2. Oxidation Aniline Black 3. Diphenyl Black 4. Aniline Black by Green's Process 1. One-bath Aniline Black A typical formula for this method is the following given by Beltzer: Aniline salt 10 kg. Sodium chlorate 1.5 kg. Copper sulphate 0.7 kg. Vanadate of ammonia 10 gr. All these substances are dissolved hot in 50 liters of water, and allowed to cool, forming solution A. Aniline salt is aniline oil which has been neutralized with the exact quantity of hydrochloric acid to form the hydrochloride. It forms white or greyish crystalline lumps very easily soluble in water. The sodium chlorate is the oxidizing agent, and the copper sulphate and the vanadate of am- monia are the oxygen carriers. 15 kg. of sodium bichromate are also dissolved in 50 liters of water, forming solution B. The bichromate is also an ozidizing agent and serves to complete the oxidation of the aniline to the black. Immediately before using, solutions A and B are mixed together, both being cool. In general practise it is cus- tomary to mix only small quantities at a time, as a con- siderable precipitate forms when the whole batch is mixed at once, the precipitate being so much waste dye substance. Usually a liter of A and a liter of B are mixed at a time, and the furs brushed with the mixture. The brushing must be varied according as the hair is hard and stiff, or soft and tender. The hair must be thoroughly impregnated in all 149 FUR DRESSING AND FUR DYEING directions, and the penetration must not be too deep to affect the leather. With experience and dexterity satis- factory results can easily be achieved. After the skins have been properly treated, they are dried at a temperature of about 35 degrees centigrade. When dry, they are re- turned to the dye bench, where they receive another appli- cation of the dye mixture, and are again dried. This opera- tion may be repeated as often as six or seven times before a sufficiently intense black is obtained. Another way of producing the desired depth of shade with fewer applica- tions is by using more concentrated dye mixtures. Each method has its disadvantages, the greater number of brush- ings requiring the expenditure of more time and labor, and the greater concentration of the bath resulting in a con- siderable loss of dye substance due to the formation of a large precipitate when the two solutions are mixed, and moreover, not all furs can be treated with concentrated mixtures. The best results with this method usually re- quire the application of six coats of a mixture of moderate concentration. 2. Oxidation Anilijie Black In order to overcome the difficulty of employing very concentrated dye mixtures, or of making many applications of the dye, a method was devised whereby the two solutions of the previous- process, instead of being mixed together, are applied successively to the hair of the furs, the following formula, also by Beltzer, being an example: Aniline oil 10 liters Nitric acid 36° Beaume, or Hydrochloric acid 22° Beaume 20 liters Cold water 20 liters This is solution A, and is merely a solution of aniline hydrochloride, or nitrate, depending on which acid has been 150 ANILINE BLACK used. Nitric acid, although more costly than the hydro- chloric acid, is to be preferred, because it is an oxidizing acid, and so assists in the oxidation of the aniline, and be- sides, has a more beneficial effect on the hair than the hydro- chloric, in the matter of softness and luster. Sodium chlorate 4 kg. Copper sulphate 1 kg. Vanadate of ammonia 10 gr. Water 50 liters This is solution B, containing the oxidizing agent, and the oxygen carriers. Just before using, equal quantities of A and B are mixed, and the skins brushed with the mixture. The skins are then dried at 35-45° centigrade, at which temperature the color begins to develop. When almost, but not entirely dried, the skins are subjected to the action of warm vapor, which is allowed to enter the drying chamber, so as to keep the temperature about 40° centi- grade, the color developing better in this way. This opera- tion may be repeated, or the skins are directly treated with a solution of 25 kg. of sodium bichromate in 100 liters of water, to complete the oxidation. The moist skins are ex- posed to the air for a time, and then dried at 35° C. This method of dyeing has several advantages over the One-bath Aniline Black. It requires fewer brushings, and enables the complete utilization of the dye solutions with- out loss. With three applications of the dye mixture by the Oxidation process, as deep and intense a black can be obtained as with six brushings by the One-bath method. The dyeings, too, are nearly, but not fully as brilliant and even as in the latter case. The greater the number of coats of dye that are applied the more regular will the dyeing be. 151 FUR DRESSING AND FUR DYEING 3. Diphenyl Black In 1902, the Farbwerke Hoechst, a large German producer of coal tar intermediates and dyes, invented an Aniline Black process to which they gave the name Diphenyl Black. The chief departure from the previous Aniline Black methods was the replacing of part of the aniline oil of the dye mixture by Diphenyl Black Base I, which is para- aminodiphenylamine. This base has the property of being oxidized to Aniline Black, just like aniline oil, and the ad- vantage claimed for the Diphenyl Black is that it produces an absolutely ungreenable black. The method of application is practically the same as for the other Aniline Black proc- esses, chlorates being used as the oxidizing agents, in the presence of oxygen carriers such as salts of copper and van- adium. The use of bichromates is dispensed with. On account of the comparatively high cost of the Diphenyl Black Base I, this method has not found very extensive application, especially as highly satisfactory ungreenable blacks can now be produced by other methods. 4. Aniline Black by Green's Process In 1907, Green, who has done much work in the direction of elucidating the character of the Aniline Black process, obtained a patent for a method of applying Aniline Black in a manner which was different from all the previously known formulas. The invention created great interest, and although in its original form it did not find a wide application, many of the methods used at the present time are in one way or another derived from the idea of Green. A resume of the patent will therefore be given here: " The invention relates to the production of an Aniline Black, the new process differing from all other known processes by the fact that the oxidation of aniline is effected solely or mainly by the oxygen of air. The possibility of dispensing 152 ANILINE BLACK with an oxidizing agent depends on the discovery that the addition of a small quantity of a para-diamine, or of a para- amido-phenol to a mixture containing aniline and a suit- able oxygen carrier, such as a salt of copper, greatly acceler- ates the oxidation of the aniline by the atmospheric oxygen. Further, whereas in the ordinary processes of Aniline Black, the quantity of mineral acid employed cannot be materially reduced below the proportion of one. equivalent to one equivalent of the base, under the new conditions the mineral acid may be wholly or partially replaced by an organic acid such as formic acid, without the quality of the black being materially affected. As suitable oxygen carriers the chlorides of copper have been found to give the best results, it being preferrable to use the copper in the form of a cuprous salt. This is effected by adding to the dye mixture cupric chloride, together with a sulphite or bi- sulphite in sufficient quantity to reduce the cupric salt to the cuprous state, and a sufficient quantity of a soluble chloride to keep the cuprous chloride in solution. Among the compounds suitable for the production of this black in conjunction with aniline are, para-phenylene-diamine, di- methyl-para-phenylene-diamine, para-amido-diphenylam- ine, para-amido-phenol, etc.," This method may be used alone as the other Aniline Blacks, or the dyed skins may be after-dyed in a bath con- taining a logwood dye, or it may be used in conjunction with mineral dyes, or with the Oxidation Colors, (see next chapter). A typical formula for the black by Green's process is the following: Para-amido-phenol 0.5 kg. Aniline oil 10 liters Hydrochloric acid 22° Be. 10 liters Acetic acid 40% 5 liters Cold water 25 liters 153 FUR DRESSING AND FUR DYEING This is solution A. Solution B is prepared by dissolving Copper sulphate 2 kg. Salammoniac 10 kg. Cold water 50 liters A and B are mixed, and the mixture applied to the hair of the furs several times, dryig each time at 35°-40° C. After three coats of dye have been applied, a pretty and fairly intense black shade is obtained, which is developed further by treating with a solution of 25 grams of sodium bichro- mate per liter of water. The skins are then allowed to dry in air, and then if desired, an after-dyeing is made with some other dye. On account of its extreme fastness. Aniline Black, pro- duced by any of the methods outlined above, has attained a justifiable popularity for the dyeing of furs, in spite of the necessity of using the more or less cumbersome brush method of applying the dye. Very recently there was issued to a German company a patent in which is described a method whereby furs can be dyed with Aniline Black by the dip process. An abstract of the patent (D. R. P. 33402) is as follows: ''As is known, aniline salt, and similar salts, to- gether with oxidizing agents like bichromates, chlorates, etc., cannot be used for dyeing furs by the dip process, be- cause the strongly dissociated mineral acid is injurious to the leather. The dissociation of the acid can be reduced by adding neutral salts, like common salt, or Glauber's salt, so that good results can be obtained by dyeing in a bath of the dye mixture, the leather retaining its softness." Thus far there have been no reports of the successful practical application of this patent, so its value cannot be discussed. It is extremely doubtful, however, that furs will ever be dyed in the dyebath with the present type of Aniline Black formulas, no matter what substances are added to prevent the leather from being affected. 154 CHAPTER XV FUR DYEING I Oxidation Colors THE year 1888 may be considered the beginning of a new era in the history of fur dyeing; the com- mencement of a period which was to see the time- honored, traditional methods of the masters of the art give way to newer methods of an entirely different character; and moreover, the initiation of an age when science with its basis of fact and logic, was to undertake the rationaliza- tion of an industry which had hitherto worked upon a more or less irrational, empirical and uncertain comprehension of the fundamental principles involved. It was not the work of a single day, or even of a year which brought about the virtual revolution in the dyeing of furs, but the result of long, patient, systematic effort. About this time, the German coal tar industry was attaining its real stride along the path of progress and achievement, and had already succeeded in reaching, to an appreciable degree at any rate, most users of coloring matters, with the consequence that the natural dyes, with their time and labor-consuming processes of application were gradually being superseded by the new synthetic dyestuffs which could be simply and quickly applied. It was now the turn of the fur dyeing industry to receive the attention of the scientists and tech- nologists responsible for the growth of the coal tar dye in- dustry, and so there appeared in the above-mentioned year, the following patents, taken out by a German chemist named Erdmann: D. R. P. 47349 A Process for Dyeing Hair and Feathers 155 FUR DRESSING AND FUR DYEING If white hair or feathers are soaked in an aqueous or alcoholic solution of para-phenylene-diamine, and then ex- posed to the slow oxidation of the air, or are treated in a second solution with some oxidizing agent, then the hair or feathers will be dyed. According to the oxidizing agent chosen, and the concentration of the solution used, the color obtained will be light or dark, varying from the palest blond to the deepest blue-black. Particularly suitable as oxid- izing substances are ferric chloride, permanganates, chlo- rates, hypochlorites, bichromates, and hydrogen peroxide. The dyeings are fast, that is, they do not come off, and the color cannot be removed by washing. Following examples may serve to make the process clear : 20 grams pure para-phenylene-diamine and 14 grams caustic soda are dissolved in a liter of water. The hair, previously degreased, is soaked thoroughly in this solu- tion, and while moist is entered into a three per cent solution of peroxide of hydrogen. The action is not instantaneous, but after a day, the hair is dyed a dark shade; by repetition of these operations a blue-black is obtained. The para-phenylene-diamine can be replaced in this proc- ess by other similar bases, such as dimethyl-para-phenylene- diamine, as well as the naphthylene-diamines. Since the substances which can be applied by this process are unin- jurious, the method described can be used to dye human hair on the head or beard, and so seems suited to replace for the dyeing of hair, the metallic salts and various pyro- gallic solutions which are on the market, and which are harmful to the health. D. R. P. 51073 Supplement to 47349; Process for Dyeing Hair This patent was an extension of the original patent to include certain oxy and amido-oxy compounds, the method 156 OXIDATION COLORS being essentially the same otherwise as in the original patent. An illustration of the process is as follows: 73 grams para-amido phenol hydrochloride are dissolved with 40 grams caustic soda in a liter of water. The solu- tion dyes hair a golden-yellow, which on subsequent treat- ment with a solution of ferric chloride turns to a red-brown. In these two patents is to be found the basis of the modern fur dyes and fur dyeing methods. It is interesting to note that furs were not mentioned at all in connection with the process, which was intended mainly for dyeing hair, especially on the human head. It was only several years later that the value of the method for dyeing furs was realized. So about 1894, the Aktien Gesellschaft fiir Anilinfabrikation put upon the market three fur dyes under the trade name Ursol, Ursol D, giving dark-brown to black shades; Ursol P, giving red-brown colors; and Ursol C, giving a yellowish-brown shade. Pyrogallic acid had been previously used as a hair dye, and also to a slight extent as a fur dye, so it was used in conjunction with the Ursol dyes for shading purposes. The new fur dyes were not dyes in the ordinarily accepted sense of the term. They were really coal-tar intermediates, substances similar in character to aniline, and their dyeing property depended on the fact that they could be oxidized either by atmos- pheric oxygen, or by means of oxidizing agents, forming colored insoluble products. When the oxidation of the intermediate was caused to take place on the hair the colored product formed on and in the hair fibre, and re- mained fast. The reactions bringing about the conversion of the intermediate to the colored insoluble compound are quite analogous to those of the Aniline Black process, though possibly not so complicated, with the important dif- ference, however, that, while in the production of Aniline Black acid is essential, in the present instance the oxida- tion can be carried on in neutral or even alkaline medium. On account of the character of the method used in applying 157 FUR DRESSING AND FUR DYEING the new fur dyes, the name Oxidation Colors has been given to them. Strictly speaking, Aniline Black is also an Oxida- tion dye, but it is usually considered in a class by itself. The methods used at first in the application of the Ursol dyes to furs followed closely the process as described in the patents. The furs were first killed, usually by brushing on a lime mixture, drying, and then beating out the dust. This operation was repeated, if necessary. Then a solu- tion of the desired dye, mixed with an equal volume of 3% peroxide of hydrogen was brushed on and the fur allowed to lie exposed to the air. The dyeing could also be done by the dip process, less concentrated solutions being used. By varying the concentration of the solution, and prolong- ing or shortening the time of action, the shades could be varied from very light to very dark, and by combining two or more of the Oxidation Colors, many different color effects could be produced. Soon other fur dyes were de- veloped and put on the market; for example, Ursol DB, giving blue to blue-black shades, and Ursol 2G, yielding yellowish tones suitable for mixing with the other colors. Ursol C was discarded shortly after its introduction. The dyeings obtained with the Oxidation Colors seemed to be very fast, resisting successfully the action of cold or hot water, or even hot soap solution. Moreover, a dyed hair examined under the microscope appeared to be colored through the epidermis to the medulla, and no individual particles of dye could be discerned. The new fur dyes had many evident advantages over the coloring matters in general use at the time. The simplicity of the dyeing operations, the short duration of the process, the great tinctorial power of the new products, were facts which strongly recommended themselves to the progressive fur dyer. The cost of the dyes was higher than that of the vegetable dyes, but this consideration was largely over- balanced by the saving in time and labor in using them. And yet, the Ursol dyes found only a comparatively small 158 OXIDATION COLORS market. The majority of fur dyers, always conservative and reluctant to turn from the traditional ways of the in- dustry were skeptical of, and even hostile towards the new dyes and the new methods of dyeing. In a sense, this oppo- sition was justifiable. It was not an easy task to relinquish all at once methods which had been successfully applied for generations back, and with which they were thoroughly ex- perienced, in favor of processes which were radically differ- ent, and with which they had no experience at all. But some enterprising spirits among the fur dyers undertook to try out the new products and it was not long before the skeptics had good cause for condemning the work and achievements of the chemists as far as fur dyeing was con- cerned. The new type of dyes did possess some of the advantages claimed for them, but they also possessed many highly objectionable features, which had never been mani- fest with the vegetable dyes. First of all, the dyeings were not so fast as had at first appeared, for the color came off the hair when the furs were rubbed, brushed or beaten. Then it was observed that after a short time some of the dyeings changed color, and at the same time the hair lost its gloss and became brittle. The condition of the leather after dyeing was anything but satisfactory. Most serious of all, however, was the appearance among the workers in the dyeing establishments, and also among the furriers who worked with the dyed skins, of certain pathological condi- tions which had hitherto been unknown. Various skin diseases, eczemas, inflammation of the eyes, asthmatic affec- tions and intestinal irritations were some of the afflictions which were directly attributable to the use of fur dyes of the Ursol type. Medical science was at a loss to know how to treat these ailments, because their nature was not under- stood. Here indeed, were obstacles threatening to destroy all the hopes which the discovery of the new class of dyes had aroused, and to check at the outset the possibility of rational 159 FUR DRESSING AND FUR DYEING progress in the fur dyeing industry. But the men of science were not content to let the matter drop thus. Difficult problems had been solved before, and surely there must be some way of overcoming the objections and deleterious features of a system of fur dyeing which had so much po- tential merit. Where hindrances sprang up in the path of progress, it was the duty of the chemist to remove them, and when difficulties arose, it was up to him to resolve them, as far as was humanly possible. So the chemists who had been responsible for the introduction of the Oxidation Colors set themselves to the task of eliminating the un- desirable or injurious qualities. It was many years before the results of painstaking effort and persistent study cleared up the causes of all the objectionable aspects of the fur dyes, and suggested means of overcoming them satisfac- torily. The work had been directed to the improvement of the dyes and of the methods of dyeing with them. Purer intermediates were produced, and more easily soluble ones, so that there would be no possibility of ultra-microscopic particles of the dye being deposited on the surface of the hair from the dye solution, instead of being taken up within the hair fibre. It was this superficial deposition of minute crystals of the dye or of the only partially oxidized inter- mediate, on the hair, crystals so fine as to be invisible in the ordinary high-power microscope, which caused the color to come off when the furs were brushed or beaten, giving rise to a dust which was frequently very injurious to the health. Then, mordants were adopted to help fix the dyes, compounds of copper, iron, and chromium being used as formerly with the vegetable dyes, and the range of shades was also increased thereby. Certain of the Oxidation Colors had a tendency to sublime off the hair, so the dyed hair was chemically after-treated in such cases to prevent this. The causes of the pathological aspects of dyeing with the Oxidation fur dyes were not so readily disposed of. But the adoption of devices to prevent the formation and 160 ' OXIDATION COLORS circulation of dust during the handling of the dye, the em- ployment of adequate protection against contact with the dye or its solutions, the use of the most dilute solutions possible in dyeing, the thorough washing of the dyed skins to remove any excess of the coloring matter, the prevention of dust formation in the drying of the skins, and the rigid observance of, and adherence to hygienic laws, were all factors in the elimination of the health-impairing phases of dyeing with the Oxidation Colors. It was only after all these improvements had been accom- plished that the fur dye intermediates began to acquire a degree of popularity among fur dyers, and strange as it may seem, there was a more ready market for these dyes in America, than in Germany where they were manufac- tured. Other manufacurers of coal-tar intermediates also began to produce fur dyes, and so, in addition to the Ursols, there were the Nako brand, the Furrol brand, the Furrein brand, and one or two others. New dyes were invented, until the whole range of colors suitable for fur dyeing had been produced. The black dye, however, presented some difficulty. A black dye which would rival logwood blacks could not be attained. Ursol DB in conjunction with Ursol D was being used to produce bluish-blacks, but the dyeings were not fast, turning reddish after a time. In 1909, a patent was taken out for a dye mixture, which was made up like the DB brand, but instead of using toluylene diamine with para-phenylene-diamine, the new dye was made up of a methoxy, or ethoxy-diamine with para-phenyl- ene-diamine, and it yielded brilliant bluish-blacks, which were fast, and which very nearly approached the logwood black in luster, intensity, and bloom. For some purposes, however, the production of a black color is still dependent on. the use of the logwood dye. When the Great War cut off to a large degree the im- portation of skins dyed in Europe, the American fur dyeing industry developed tremendously, and in a comparatively 161 FUR DRESSING AND FUR DYEING short time was able satisfactorily to accomplish in the way of dyeing furs, what had taken foreign dyers a much longer period to attain. It had been previously considered that furs could be dyed properly only by European fur dyers, but the achievements in this direction by Americans fully dispelled this belief. But the success of the fur dyers in America might not have been so marked or rapid, had it not been for the work of the American chemists. The war had also shut off the supply of German dyes, upon which the dyeing industries of America had formerly been de- pendent, so enterprising chemists in this country undertook to fill the need, and in a surprisingly short time, American fur dyes, in every respect the equal of the foreign product were offered to the American fur dyers, and at the present time, the requirements of the fur dyeing industry in this country are being adequately met by domestic producers. Among the brands on tha market are the Rodol, Furamine, Furol, and several others. The Oxidation Colors are now being offered in a high state of purity, and easily soluble, free from any poisonous constituents, and there is abso- lutely no reason for the appearance of any pathological con- ditions among workers on dyed furs, or users of such furs, provided the necessary precautions have been taken in the dyeing process. The occurrence of any affection which can be traced to dyed fur, cannot possibly be due to the dye itself, but to gross carelessness and negligence in dyeing, and in any such event, the dyer responsible should be brought to account. In order to get a better understanding of the nature and action of the Oxidation Colors, a typical one will be studied in some detail. The most important one in this class is para-phenylene-diamine, usually designated by the letter D in all commercial brands of this fur dye, while its chemical formula is represented as CeHi (NHo).. When pure it occurs in colorless, crystalline lumps, which rapidly turn brown when exposed to the air; the technical 162 OXIDATION COLORS product of commerce is of a dark-brown color. It dissolves readily in hot water when pure, and also in acids. At one time the hydrochloride was used instead of the free base, on account of its greater solubility, but now a base is made which is sufficiently pure to be very soluble in water. There are several methods of preparing para- phenylene-diamine: first, by the reduction of amido-azo- benzol, the product obtained in this way always containing a slight amount of aniline, which reduces the solubility, and also gives rise to poisonous oxidation products during the dyeing process; second, by the reduction of paranitraniline, the quality and solubility of the product in this case de- pending on the purity of the starting material; and third, by the treatment of para-dichloro-benzol with ammonia under pressure, the best product being obtained by this method. The crude para-phenylene-diamine, made by any of the above processes, is generally distilled in vacuo, the refined base being obtained as lumps with a crystalline fracture. The first step in the oxidation of the para-phe- nylene-diamine is the formation of quinone di-imine, NH:CoH4:NH. This is a very unstable compound in the free state, and even in aqueous solution it decomposes within a comparatively short time, or combines with itself to form a more stable substance. Quinone di-imine has a very sharp, penetrating odor, and produces violent local irritations wherever it comes in contact with the mucous membrane. If a small quantity of para-phenylene-diamine is absorbed into the human body, by breathing the dust, or otherwise, the formation of quinone di-imine takes place internally with consequent irritation of the mucous lining throughout the body. The various pathological conditions mentioned before may be ascribed to irritation caused by quinone di-imine. In any dyeing process where there is a possibility of the formation of quinone di-imine, as is the case with most dyes containing para-phenylene-diamine, 163 FUR DRESSING AND FUR DYEING special precautions must be taken by the workers in hand- ling the dye or coming in contact with its solutions, and no one who is particularly sensitive to irritation should be per- mitted to work in a place where such dyes are used. The next step in the oxidation of the para-phenylene- diamine is the formation of what is called Bandrowski's base. Three parts of the quinone di-imine combine with themselves, forming a substance of a brown-black color, which was formerly regarded as the final oxidation product. The formula of Bandrowski's base is represented by the fol- lowing chemical hieroglyphics: (NH,),.CeH3.N:CoH,:N.CeH3(NH.),. Further investigation has shown that the oxidation pro- ceeds beyond this stage with the formation of a compound of what is known as the azine type, which is depicted by the chemist as (NH3).CeH3 CeH.CeH3.NH,. It is by no means certain that this substance is the true coloring matter obtained by the oxidation of para-phenyl- ene-diamine, for the reactions may continue still farther, producing even more complicated oxidation products. Scientific research and study has not as yet gone beyond this stage. The reactions of the other dyes of the Oxidation type are quite similar to those of para-phenylene-diamine, some being simpler, and others being even more complex. The presence of certain chemical groups in the intermediate, or the relative position of such groups are factors re- sponsible for the variations in shade. With the various mordants, the Oxidation Colors give different shades, and a great range of colors can be produced either by combining mordants, or combining dyes, or both. The following tables illustrate the shades formed with the customary mordants. 164 OXIDATION COLORS Chbome Copper Iron Direct Ursol D brown black coal black coal black dark brown to brown black Ursol P dull red brown dull dark brown grey brown light brown Ursol 2G yellow brown d u 1 1 y e 1 1 w brown yellow brown dull yellow Ursol A blue black blue to blue- black Ursol 4G light brown medium brown yellow pure yellow Ursol 4R orange brown light yellow brown red brown orange red Ursol Grev B greenish grey greenish grey mouse grey Ursol Grey R brownish grey brownish grey reddish grey Fur dyes of American make being equal in every way to the German product, show the same color reactions with the various mordants. The following table shows the shades produced with the same mordants as above: Chrome Copper Iron Direct Rodol D Rodol P Rodol 2G Rodol 4G Rodol A Rodol Grey B Rodol Grey R brown black red brown yellow brown light brown greenish grey greenish grey coal black dark brown yellow brown light brown blue black greenish grey brownish grey coal black grey brown yellow brown reddish brown mouse grey mouse grey brownish black light brown dull yellow pure yellow blue black All these shades are produced by dyeing in a bath con- taining a 7ieutral solution of the dye. Sometimes the dye comes in the form of a salt of a mineral acid, like hydro- chloric or sulphuric acid, in which case a sufficient amount of an alkali, usually ammonia, is added to liberate the free 165 FUR DRESSING AND FUR DYEING base. According to the Cassella Co., German manufac- turers of the Furrol brand of fur dyes, the dyeing can also be carried on in slightly alkaline or in slightly acid solution, a different series of shades being obtained in each instance. Ammonia is used to render the bath alkaline, and formic acid to make it acid. The most customary practise, how- ever, is to use neutral solutions of the dyes. For preparing the mordant solutions much smaller quantities of the metallic compounds are used than in the case of the vegetable dyes. With chrome mordants cream of tartar is always employed as an assistant, and occasion- ally also with copper and with iron mordants. With copper, and also with iron mordants no addition is made at all, or sometimes a small quantity of acetic acid is added. The temperature of the mordant solution is kept about 30° C, and the duration of the mordanting varies from 2-24 hours according to the depth of shade desired. The concentra- tion of the solution may also be varied, it sometimes being just as well to use a strong mordant solution and less dura- tion of mordanting. Chrome may be combined with copper, and iron may be combined with copper, but chrome and iron do not go together as mordants. Some typical average mordanting formulas are as follows : Chrome mordant. Bichromate of soda 2.5 gms. Cream of tartar 1.5 gms. Water 1 liter Copper mordant. Copper sulphate 2 gms. (Acetic acid 50% 2 gms.) Water 1 liter - 166 OXIDATION COLORS or, Iron mordant. Ferrous sulphate 2 gms. (Acetic acid 50% 2 gms.) Water . 1 liter Iron pyrolignite 30% 10 gms. Water 1 liter Chrome-copper mordant. Bichromate of soda 2 gms. Copper sulphate 0.25 gms. Cream of tartar 1.0 gms. Water 1 liter Copper-iron mordant. Copper sulphate 2 gms. Ferrous sulphate 2 gms. (Acetic acid 50% 2 gms.) Water 1 liter The killed skins are immersed in the mordanting solution, and allowed to remain the required length of time. They are then thoroughly rinsed to remove any excess of the mordant, and are hydro-extracted. Under no circumstances should mordanted skins be permitted to dry, for they would be unfit for use again. The dyebath is next prepared by dissolving the necessary quantity of the dye, varying from 0.1 gm. to 10 gms. per liter. Then if the solution must be neutralized, the am- monia is added and the temperature of the bath is brought to 30-35° C. by the addition of cold water. This tempera- ture is maintained throughout the dyeing operation. To the solution is added the oxidizing agent. Ordinary commercial 167 FUR DRESSING AND FUR DYEING peroxide of hydrogen containing 3% by weight is the usual oxidizer, although perborates have been suggested, 15-20 parts of peroxide of hydrogen for every part of dye are added, and the dye solution brought to the proper dilution. As soon as the dyebath is ready, the skins are entered, and worked for a short time to effect even penetration. They are then left in the dyebath for 2-12 hours or longer according to the depth of shade. After being satisfactorily dyed, the furs are rinsed thoroughly, hydro-extracted and dried and finished. Where the dye is to be applied by the brush to the tips of the hair, stronger dye solutions are used, the brushed skins being placed hair together and let lie for about 6 hours in order to permit the color to develop, after which the furs are dried and drum-cleaned. Some shades, particularly black, have a tendency to rub off slightly. In order to overcome this, the dyed furs, after rinsing, are treated with a cold solution of ^ part of copper sulphate per 1000 parts of water, for 3-4 hours, then without rinsing, hydro-extracted and dried. Furs which have been tipped are brushed with a 1-2% solution of copper sulphate and dried. Care must be taken in this after-treat- ment, for the use of too strong a solution of copper sulphate, or too prolonged action of such a solution will materially alter the shade of the dyed fur. A few typical formulas will serve to illustrate the general methods of employing the Oxidation Colors: Brown Sable Imitation on Unsheared Rabbit ' The skins are killed with soda, soured, and washed, then mordanted with Bichromate of soda 2 grams Copper sulphate .25 grams Cream of tartar 1 gram Water 1 liter 168 OXIDATION COLORS for 24 hours. Then washed, and dyed for 24 hours with Fur Brown 2G ^ 3 grams Hydrogen peroxide 45 grams Water 1 liter Wash and dry the skins, then brush the tips with Fur Brown D ^ 20 grams Hydrogen peroxide 400 grams Water 1 liter Black on Sheared Muskrat The skins are killed with soda, soured, and washed, then chrome mordanted for 6 hours. Then they are dyed for 6 hours with Rodol P 1.5 grams Pyrogallic acid .7 grams Ammonia 2.0 grams Hydrogen peroxide 45 grams Water 1 liter The dyed skins are washed and dried, then tipped with Rodol D 20 grams Rodol DB 2 grams Hydrogen peroxide 450 grams Water 1 liter Brown on Thibet Sheep Skin The killed skins are mordanted for 6 hours with a chrome mordant, then dyed for 6 hours with Ursol P 1 gram Pyrogallic acid 1 gram Ammonia 2 grams Hydrogen peroxide 40 grams Water 1 liter ^ Inasmuch as most manufacturers use the same letters to designate the various dyes, any equivalent brand of fur dj'e may be used in place of those here mentioned. 169 FUR DRESSING AND FUR DYEING It is also possible to combine dyeings with the Oxidation Colors with Vegetable dyeings, or with Aniline Black. For example, if it be desired to produce an imitation skunk on a raccoon, and an exceptionally fast and intense and lustrous black on the tips of the hair, the skins are dyed in the bath with the Oxidation dyes, and the tips of the hair are brushed with a mixture such as described under Vege- table Colors for the production of French seal, as follows : Imitation Skunk on Racoon c The skins are killed with caustic soda, soured and washed, then mordanted with an iron-copper mordant as described, and then dyed with Fur Grey R 3 grams Ammonia 2 grams Peroxide of hydrogen 45 grams Water 1 liter After washing and drying, the dyed skms are brushed over with a mixture such as used for dyeing French seal with Vegetable Colors. In a similar manner, the Oxidation Colors may be used to give a base color to furs dyed by the Aniline Black process. It is apparent from these few illustrations that a great variety of shades can be produced, and the dyeing of imita- tions of the better class of furs on cheaper skins is a com- paratively simple matter, after an understanding of the nature of the dyes has been obtained, and a certain amount of skill acquired in working with these dyes. 170 CHAPTER XVI FUR DYEING Coal Tar Dyes IN addition to the Aniline Blacks and the Oxidation Colors already discussed there are certain of the syn- thetic coal tar dyes such as are generally used in the dyeing of textiles, which can also be applied on furs. There are several classes of these dyes, varying somewhat in their nature, and consequently in their manner of application; in the main they produce bright shades, such as are but seldom used on furs, yet which may occasionally serve for the production of novel effects. Basic, acid and chrome colors are the types which can be employed. Basic colors possess great fullness and tinctorial strength, but have a tendency to rub off. and the tips of the hair take a darker shade with these dyes than the rest of the hair. The addition of acetic acid and Glauber's salt to the dyebath will result in a more uniform dyeing. On account of the comparatively poor fastness to rubbing and washing, basic dyes are used only for dyeing furs which are intended for cheap carpet rugs, such as sheep and goat. They may also find use in the production of light fancy shades on other white furs. The procedure is usually as follows: The furs are killed in the customary manner with soap and soda or ammonia, or if this is insufficient, with milk of lime. A soap-bath is then prepared containing 2.5-6 grams of olive- oil soap per liter of water. The temperature of the bath is brought to 40° C. To this is added the solution of the dye- stuffs, prepared by mixing the required color or colors with a little acetic acid to a paste, and then pouring boiling water 171 FUR DRESSING AND FUR DYEING on the mixture until dissolved. Undissolved particles or foreign matter are removed by passing this solution through a cotton cloth or sieve, and the clear solution then mixed with the soap-bath. The well-washed skins are then entered into the dyebath and immersed for about half an hour, or until the desired depth of shade is obtained. They are then removed, pressed or hydro-extracted and dried. For the production of light shades, the following dyes may be used: For cream, light sulphur-yellow, maize, salmon, etc. Combinations of Thioflavine Rhodamine B Irisamine G For greenish-yellows Combinations of Thioflavine Victoria Blue B For light pink Rhodamine B Irisamine Rose Bengal Extra N For purple Methyl Violet 3B-6B Crystal Violet For sky-blue Victoria Blue B For white Victoria Blue B (Milk-white) Methyl Violet 3B-6B Crystal Violet (Ivory-white) 172 COAL TAR DYES To produce very delicate shades, the moist dyed skins are subjected to a sulphur bleach overnight, to lighten the color, then rinsed, and dried. Full, brilliant shades may be ob- tained by dyeing in a bath of 40° C, acidulated with 2-3 grams of acetic acid per liter of solution, the following dye- stuffs being suitable: For yellow to orange Thioflavine Paraphosphine Rhodamine Safranine New Magenta For pink Rhodamine B Rose Bengal Extra N For light red Safranines For bordeaux and red Magenta New Magenta Russian Red Cerise For violet For blue Methyl Violet 6B-4R Crystal Violet 5B Victoria Blue B Methylene Blue BB New Methylene Blue N 173 FUR DRESSING AND FUR DYF^ING For green Malachite Green Crystals Brilliant Green Crystals, or combinations of Thioflavine Diamond Phosphine Victoria Blue B For brown Chrysoidines Bismarck Browns In dyeing skins with harder hair than that of sheep or goat, mere killing is insufficient to render the hair capable of taking up the dye. The skins are therefore immersed before dyeing, in a cold, weak solution of chloride of lime, the affinity of the hair for the dye being thereby greatly in- creased. Acid dyes are employed when a greater fastness is re- quired than can be obtained with the basic colors. Sul- phuric acid in a quantity equal to half the weight of the dyestuffs used, together with four times that quantity of Glauber's salt is added to the dyebath. Formic acid may be used in place of the sulphuric acid, very good results being obtained. The skins are immersed in the dyebath, and worked until thoroughly soaked with the dye liquor, and then allowed to remain until the proper depth of shade is attained, or overnight. The temperature of the solution is about 40° C., and only very light shades can be produced in this manner. In 1900 and again in 1914, the Cassella Co., a large German manufacturer of dyestuffs, obtained patents for processes enabling the dyeing of furs in hot solution with the acid dyes. The method required that the skins be chrome-tanned in order to render them resistant to the action of hot solutions, the addition of a small amount of formaldehyde to the chrome solution increasing this effect. The skins are then treated with a solution of chloride of 174 COAL TAR DYES lime in order to increase the affinity of the hair for the dye- stuffs. The method as it is now practised is as follows: The skins which have been cleaned and washed are chrome tanned by the method as described in the chapter on Tan- ning Methods, 60 grams of formaldehyde being added to every 10 liters of the chrome solution. After proper tanning the skins are rinsed, and while still moist they are subjected to a treatment with chloride of lime. They are first im- mersed for 15 minutes in a cold bath containing 120 grams of hydrochloric acid 32-36° Twaddell per 10 liters of water, then without rinsing, they are entered into a bath made up by adding gradually in four portions the clear solution of 2-4 grams of the chloride of lime per 10 liters of water. After working for an hour, the skins are removed and entered again into the acid solution, in which they are worked for another 15 minutes. In order to neutralize and remove the last traces of the chloride of lime from the furs, they are rinsed in a luke-warm bath containing 1-2 grams of sodium thiosulphate, or hyposulphite of soda, in 10 liters of water. The skins are then rinsed again, and hydro-extracted, or pressed, and are ready for dyeing. The dyebath is prepared with the required quantity of dye, to which is added 10-20% Glauber's salt and 2-5% acetic acid (both calculated on the weight of the skins). The skins are entered at 20° C, then after three-quarters of an hour to 40° C, and then after another hour slowly to 50-55° C. For blacks, the temperature is raised as high as 65° C. After dyeing the skins are treated with a solution containing per 10 liters 90-120 grams of olive-oil soap 12-25 grams olive oil 12 grams ammonia for 15 minutes, then hydro-extracted and dried, without further rinsing. 175 FUR DRESSING AND FUR DYEING For this method of dyeing, the following dyes may be used: For yellow and orange Fast Yellow S Acid Yellows Naphthol Yellow S Tropaeoline Orange GG, R, II, IV For blue Cyanole FF Azo Wool Blue Naphthol Blue R Formyl Blue B For brown, combinations of Fast Yellow S Acid Yellows Tropaeoline DD Orange GG Lanafuchsine Indigo Blue N Cyanole B Fast Acid Green BN For reds Acid Reds Lanafuchsine Azo Orseille For violet Azo Wool Violet Acid Violets For green Naphthol Green B Fast Acid Green Cyanole Green For black Naphthylamine Blacks Naphthol Blacks Naphthol Blue-black For grey Silver Grey N Dyed with the addition of i-1% of alum The chrome colors are dyed on furs when very fast shades are desired, all the fancy colors being produced in this manner, but for black, only the acid dyes are suitable. The preparation of the skin is exactly the same as for the acid colors, except that the treatment with chloride of lime may be omitted, although for very full shades it is desirable. The dyeing is carried out as follows: The dyebath is pre- pared with the requisite amount of the desired dyestuff, which is previously dissolved, and to this is added a solu- tion of sodium bichromate, the amount of this substance being half the weight of the dye. The solution is heated 176 COAL TAR DYES and the skins entered and dyed for 1-2 hours at 70-80° C. Then the dyebath is exhausted by the addition oi ^% acetic acid, the skins being worked for another half hour, then rinsed, hydro-extracted and dried. Any of the one- bath chrome, or after-chrome colors may be used for this method. Recently methods have been patented for the dyeing of furs by means of the vat colors. Vat dyes are among the fastest coloring matters ever produced, and their appli- cation on furs would be a great advantage, if suitable shades could be obtained. The general process for dyeing with vat colors, consists in reducing the dye, which is usually very insoluble, into a soluble " leuco " compound, by means of hydrosulphites in the presence of alkalies. The leuco compound is not a dye itself, but when the fibre absorbs it, and is then exposed to the air, the leuco compound is re- oxidized to its original insoluble form, which remains fast and permanent. The use of strong alkalies in vat dyeing has hitherto been a great obstacle in the use of these dye- stuffs, but in 1917, the Farbwerke Hoechst, a large German dyeworks, patented a process as follows: "A process for dyeing furs with vat colors. The dyeing is done in solu- tions of the vat dyes (after the addition of gelatine or some other protective colloid), which are rendered neutral or only slightly alkaline with ammonia, by neutralizing the caustic soda of the solution of the leuco compound of the vat dyes by the addition of ammonium salts, or suitable acids. The dyeings thus obtained are uniform and fast, the leather is dyed to only a slight degree, and shows no deleterious effects of the dyebath on the tannage." As a practical application of this process, another patent was taken out by the same company, also in 1917, as follows: " A process for producing fast blacks on furs, consisting of dyeing a ground color with appropriate vat dyes in a hydro- sulphite vat, and after oxidation in air, topping with an Anihne or Diphenyl black. The dyeings obtained by the 177 FUR DRESSING AND FUR DYEING combination of vat dyes which are fast to oxidizing agents, with an oxidation black, have an appearance matching that of logwood black in beauty; and with a dark-blue to blue- black under-color, and a full, deep black top color, can- not be distinguished from logwood. These dyeings also have the advantage of being faster to light than logwood or other blacks." While these processes undoubtedly have many meritorious qualities which make them interesting, they do not seem as yet, to have attained any great practical application. However, it is a field of fur dyeing which is worth while developing, and with certain necessary improvements in these processes, the vat dyes may yet supersede partially some of the other methods of dyeing furs. 178 CHAPTER XVII BLEACHING OF FURS BLEACHING is for the purpose of lightening the color of furs, and is most generally applied to white- haired skins such as white fox, ermine, and occasionally white lambs of all kinds, and white bears. Among such furs, pelts of a naturally pure white tone are relatively scarce, while in the majority of cases the color ranges from a pale creamy white to a decidedly yellowish shade. Colors which vary from the pure white detract con- siderably from the attractiveness and consequent value of the fur, and indeed, some pelts are so far off shade that they can only be used when dyed a darker color. Most white skins which are but slightly inferior in color can be brought to a pure white by bleaching, and they can then be used natural. Some pelts, on the other hand, are par- ticularly resistant to the action of bleaching agents and cannot be sufficiently decolorized to render them suitable for use natural, so these are also dyed. For the production of certain delicate or fancy dyed shades on white furs, it is often necessar}^ to bleach the skins in order to be able to obtain pure tones. Such instances are not very common, however. Occasionally dark furs, such as beaver, are bleached on the tips of the hair, a golden shade being obtained thereby, which at one tune was quite popular, but recently such effects have not been in vogue. In the bleaching of furs, two steps may be distinguished, first degreasing, and second, bleaching proper. In the pre- liminary operations of fur dressing, the furs are treated with soap or weak alkalies to cleanse them and to remove excess oil from the hair. During the various processes and raa- 179 FUR DRESSING AND FUR DYEING nipulations, the hair, especially on white skins, may be- come soiled or somewhat greasy again, so it is advisable to repeat the cleaning process. This should in every case be as light as possible, using a weak solution of soap for the softer and cleaner pelts, or dilute solutions of ammonium carbonate or soda ash for the more greasy-haired skins. The skins are then thoroughly rinsed to remove all traces of the degreasing material. This step is very essential in order to obtain uniform bleaching. Broadly speaking, there are two general methods which can be used in bleaching furs, one involving the use of what are known as reducing agents, and the other employing oxidizing substances. Among reducing agents which can be used for bleaching furs are sulphurous acid, and its salts such as sodium bisul- phite and sodium sulphite; hydrosulphites, and derivatives. 1. Sulphurous acid. — When sulphur is burned, sulphur dioxide gas is formed. In the presence of moisture, or when dissolved in water, this gas forms sulphurous acid, which is one of the most commonly used bleaching chemicals for all sorts of materials, and is very effective for decolorizing furs. The procedure usually followed is to hang up the moistened skins on wooden rods in a more or less cubical chamber made of stone or brick, and lined with wood or lead. No other metals may be used, because they are quickly cor- roded by the sulphurous acid. The requisite quantity of sulphur is placed in a pot in the bleaching chamber, and then ignited, after which the doors are shut tight. The fumes of the burning sulphur in contact with the moist hair readily exert their bleaching action on the furs, and the operation is allowed to proceed for six or eight hours, or overnight. Then by means of fans or other devices, the air filled with sulphur dioxide gas is withdrawn from the chamber, and replaced by fresh air. The door is opened, the skins removed, exposed to the air for a time, then rinsed, and finally dried and finished. Sometimes one 180 BLEACHING OF FURS operation is not enough to sufficiently bleach the hair, so the process is repeated. Sulphur dioxide gas can now be obtained compressed in cylinders, which are more conven- ient to handle than burning sulphur. The flow of gas which is introduced into the bleaching chamber by means of a nozzle attached to the cylinder, can be regulated, and the bleaching thus retarded or accelerated. 2. Sodium bisulphite and sodium sulphite. — These salts of sulphurous acid are effective in their bleaching action only when in solution in the presence of acids. The acids liberate sulphurous acid from the salts, so this method is virtually the same as 1. Instead of using the salts of sul- phurous acid, sulphur dioxide may be dissolved in water, and the solution used for bleaching by immersing the furs in it. This procedure, while consuming somewhat less time than the chamber process, is more likely to affect the leather, which would have to be retanned. The principle is the same as that involved in method 1. 3. Hydrosulphites and derivatives. — The bleaching agent can be prepared by adding zinc dust to commercial bisulphite of soda dissolved in about four times its weight of water until no more reaction is evident. Milk of lime is then added to precipitate the zinc, and the clear superna- tant liquid of 1.5°-5° Tw. is used for bleaching. The skins are immersed for 12-24 hours, taken out, washed and finished. Instead of preparing the hydrosulphite, the com- mercial products may be used with greater convenience, a solution containing 1-4% of the hydrosulphite powder be- ing used, and the skins treated in this until satisfactorily bleached. The bleaching action of sulphurous acid and hydrosul- phite is supposed to be due to the reduction of the coloring matter of the hair to a colorless compound; or possibly to the formation of a colorless compound of the bleaching material with the pigment. The former seems the more probable explanation, because the change is not a perma- ISl FUR DRESSING AND FUR DYEING nent one, the original natural color returning after a long exposure of the bleached fur to air and light. However, the results are sufficiently enduring to satisfy the require- ments of the trade in the class of furs on which these meth- ods of bleaching are used. Bleaching chemicals with an oxidizing action generally used for decolorizing furs are hydrogen peroxide and per- oxides; occasionally hypochlorites and permanganates are also used. 1. Hydrogen peroxide. — Hydrogen peroxide is usually employed for bleaching in the form of its 3% solution, to which is added about 20 cubic centimeters of ammonia per liter. The ammonia serves partially to neutralize the acid which commercial peroxide generally contains, and also to facilitate the bleaching action. The thoroughly de- greased skins are immersed in the solution until the hair is completely wetted by it, are then removed, and evenly pressed or hydro-extracted, after which the pelts are hung up to dry in the air. As the hair becomes drier, the con- centration of the peroxide becomes greater, and conse- quently the bleaching action is stronger. Where there is a likelihood of the leather being affected by the bleaching solution, the ammoniacal peroxide may be applied to the hair with a fine sponge or brush until sufficiently wetted, and then hanging the skins up to dry. Repetition of the process is sometimes necessary to obtain pure white, but the results are always excellent. 2. Peroxides. — The most important of these is sodium peroxide, which comes on the market as a yellowish-white powder, which must be kept dry, and away from any in- flammable material, as fires have been caused by the con- tact of the peroxide with such substances. When dissolved in water, it is equivalent to a strongly alkaline solution of peroxide of hydrogen. 182 BLEACHING OF FURS Na.,0, + 2 H2O : = H2O, + 2 NaOH sodium water peroxide caustic peroxide of hydrogen soda When dissolved in acid, the alkali is neutralized, and a neutral solution of peroxide of hydrogen and a salt is ob- tained, and this method is used to obtain peroxide of Na^O^ + H3S04 = = H.O, + Na,S04 sulfuric sodium sulphate acid hydrogen cheaply. 3 parts of sodium peroxide are slowly dissolved in a cold 1% solution of 4 parts of sulphuric acid, stirring during the addition, and making the resulting solu- tion neutral to litmus paper, acid or more sodium peroxide being added as needed. There is then added 3-6 parts of a solution of silicate of soda of 90° Tw. The skins are im- mersed until properly bleached, taken out, passed through a weak acid solution, then washed and finished. This method generally requires the leather to be retanned after bleaching. Another process, which involves the use of peroxides, but which is not commonly practised, consists in rubbing the hair with a pasty mixture of equal parts of water, barium dioxide, and silicate of soda, hanging up the skins to dry, and then beating and brushing the hair. 3. Permanganates. — The only member of this group that finds practical application for bleaching purposes is potassium permanganate. The skins are immersed in a 0.1% solution of the crystals of potassium permanganate, until the hair acquires a deep brown color. They are then removed, rinsed, and entered into a second bath containing sulphurous acid in solution, prepared by acidifying a solu- tion of sodium bisulphite. The skins are then worked in this until fully bleached. It is the permanganate which does the bleaching, the sulphurous acid being for the pur- 183 FUR DRESSING AND FUR DYEING pose of dissolving the brown compound of manganese formed on the hair, 4. Hypochlorites. — Chloride of lime and sodium hypo- chlorite, which is prepared from the former, are the chief chemicals of this type used for bleaching. The skins are entered into a weak solution of the hypochlorite, and left until the hair is decolorized ; then after removing, they are passed through a dilute acid, and subsequently through a weak solution of sodium thiosulphate in order to remove all traces of the hypochlorite. This method causes the hair to acquire a harsh feel, and the yellow color is never entirely eliminated. The hair, however, possesses a great affinity for certain types of dyestuffs, and it is only when these particular classes of dyes are to be applied to the furs, that the hypochlorite bleach is used. (See dyeing with Acid colors). The various oxidation methods of bleaching are supposed to change the coloring matter of the hair into an entirely different and colorless compound which cannot return to its original form. The bleach is therefore permanent. In common practise, the sulphurous acid, and the perox- ide of hydrogen methods are the two chiefly employed in bleaching processes. Sulphurous acid is used to bleach the cheaper kinds of furs, while peroxide of hydrogen is applied to the finer furs. Whichever process is used, it is customary to give the bleached skins a subsequent " blueing," by passing them through a very weak solution of a blue or violet dye, such as indigo-carmine, crystal violet, alkali blue or ultramarine. The furs are then dried and finished off as usual. In drum cleaning white furs, gypsum or white sand, or sometimes even talc are used with the sawdust, or occasionally alone without the sawdust. 184 BIBLIOGRAPHY . Allen " Commercial Organic Analysis " Armour, B. R. " Fur Dressing and Dyeing " 1919 Color Trade Journal, Vol. 1, p. 51-53 Jour. Amer. Leather Chemists' Assn., Vol. 13, p. 63-69. Belden, A. L. " Fur Trade in America " 1917 Beltzer, F. J. G. " Industrie des Foils et Fourrures, etc." 1912 Revue Generale des Matieres Colorantes, Vol. 12, 1908 Bennett, H. G. " Manufacture of Leather " 1910 Bertram, P. Deutsche Fiirber-Zeitung 1895-96 Heft 17, p. 266 Bird, F. J. " American Practical Dyers' Companion " p. 241-245 Boerner, H. Kunststoffe, 1912 p. 223 Brevoort, H. L. " Fur Fibres as shown in the Microscope " 1886 Buclier, B. '' Geschichte der technischen Kiinste " 1875-1893 Cubaeus, P. " Das Ganze der Kiirschnerei " 1912 Davis, C. T. " Manufacture of Leather " Erdmann, E. Deutsche Fiirber-Zeitung 1894-95 Heft 21, p. 337 Zeitschrift fiir angewandte Chemie, 1895, Heft 14 Zeitschrift fiir angewandte Chemie, Heft 35, 1905 ■ ■ Berichte, 1904, 37, p. 2776, 2906 Farrell, F. J. "Dyeing and Cleaning" 1912 Fougerat, L. " La Pelleterie dans I'antiquite, la prehistoire, etc." Fleming, L. "Practical Tanning" 1916 Gardner, W. M. "Wool Dyeing" 1896 Grandmougin, E. Zeitschrift fiir Farben-Industrie, 1906, 5, p. 141 Gruene, E. Deutsche Fiirber-Zeitung, 1895-96 Heft 13, p. 197 Halle " Werkstatte der heutigen Kiinste," 1762, Vol. 2, p. 317 Hartwig, O. L. " Sprengler's Kiinste und Handwerke," 1782 Hausman, L. A. Scientific Monthly, Jan. 1920; March, 1921 Natural History, Vol. 20, 4, 1920 American Journal of Anatomj^ Sept. 1920 American Naturalist, Nov.-Dec. 1920 Hayes, A. H. National Cleaner and Dyer, Nov. 1920, p. 55-57 Jacobson, " Schauplatz der Zeugmanufacturen " p. 493 Jones, J. W. " Fur Farming in Canada " 1913 Knecht, Rawson & Loewenthal " Manual of Dyeing" 1916 Kobert, R. " Beitrage zur Geschichte des Gerben und der Astringentien " 1917 Koenig, F. Zeitschrift fiir angewandte Chemie, 1914, Vol. 1, p. 529 Lamb, M. C. "Dressing of Leather" 1908 185 BIBLIOGRAPHY Jour. Soc. Dyers & Colourists 1913. 29, p. 160-165 Lamb, J. W. Jour. Soc. Dyers & Colourists Dec. 1905, p. 323 Larish & Schmid "Das Kuerschner Handwerk " 1-3 Laut, A. C. " The Fur Trade of America " 1921 Martin, G. '' Industrial Organic Chemistry " Lightfoot, J. " The Chemical History & Progress of Aniline Black " 1871 Mairet, E. M. " A Book on Vegetable Dyes " 1916 Matthews, J. M. " Application of Dyestuffs " 1920 Mayer, A. " Die Farberei in der Werkstiitte des Kiirschners " Mierzinski, S. " Die Gerb und Farbstoffextrakte " Noelting & Lehne " Anilin-Schwarz " 1904 Perkins & Everest " Natural Organic Coloring Matters " 1918 Petersen, M. ''The Fur Traders & Fur-Bearing Animals" 1920 Poland, H. " Fur-Bearing Animals in Nature and Commerce " Proctor, H. " Leather Industries Laboratory Book " " Tanning " " Making of Leather " Schlottauer, E. Deutsche Farber-Zeitung 1911, Heft 20, p. 397 Deutscher Farber-Kalender 1911, p. 65 Leipziger Farber-Zeitung 1909, p. 441 Schmidt, C. H. " Handbuch der Weissgerberei " Setlik, B. Deutsche FUrber-Zeitung 1901. p. 213 Smith, R. W. Color Trade Journal Vol. 3, Sept. 1918, p. 304-310 Textile Recorder, Vol. 36, p. 292-293, Dec. 1918 Revue Generale des Matieres Colorantes, Vol. 23, p. 32-36 Stevenson, C. H. " U. S. Fish Commission Report 1902-1903, Bulletin No. 537 Stickelberger, E. " Geschichte der Gerberei " 1915 Strasser " Chemische Farberei der Rauchwaren " 1879 Ullmann " Enzyklopedie der technischen Chemie " Villon, A. M. " Traite pratique de la fabrication des cuirs, etc." 1900 Werner, H. " Die Kiirschnerkunst " 1914 " Das Farben der Rauchwaren " 1914 Whittaker, C. M. " Dyeing with Coal Tar Dyes " 1919 Wiener, F. " Weissgerberei " 1877 Witt-Lehman '' Chemische Technologie der Gespinst-Fasern " 1910 Zeidler, H. " Die moderne Lederfabrikation " 1914 186 INDEX Acetate, aluminum, IIS chromium, 120 copper, 120 ferrous, 119 lead, 126 Acetic acid, 112 Acid dyes, 174 Acids, action of, on hair, 29 on skin, 26 After-treatment with copper, 168 Alaska fox imitations, 143 Alkaline aluminum mordants, 122 chromium mordants, 123 iron mordants, 123 Alum, 32, 53, 118 chrome, 57 chrome tans, 64 tans, 54, 56 Aluminum acetate, 118 ■ mordants, 118 sulphate, 53, 118 Ammonia, 110 Ammonium sulphide, 126 Aniline black, 144 by dip process, 154 chemistry, 145 Green's process for, 152 nature of, 144 One-bath, 149 Oxidation, 150 ■ processes, 149 ungreenable, 148 Aniline oil, 145 Astrachan 5, 7, 12 Bacteria, 51 Badger, 7 Ball-drum, 62 Bandrowski's base, 164 Basic dyes, 171 Beam, 38 Beaming, 38 Bear, black, 5, 7 brown, 5, 8 white, 8 bleaching of, 179 Beating furs, 79 Beaver, 5, 8, 25, 83, 94 Beechwood ashes, 108 Bichromate of soda, 121, 147 Black, aniline, 144 by Green's process, chemistry of, 145 nature of, 144 One-bath, 149 Oxidation, 150 ungreenable, 148 Black, diphenyl, 152 logwood, 139 on Chinese goats, 141 on lambs, 141 on raccoon, 130 . on skunk, 130 on wolf, 130 Bleaching of furs, 179 Blending, 91, 104 Blue-grey on white furs, 142 Blueing," 184 Blue salt, 120 vitriol, 119 Borax, 39, 58 Brasilein, 135 Brasilin, 135 Brazilwood, 135 Bright shades on furs, 171 Broadtail, 8, 12 dyeing of, 139 Brown on Thibet sheep, 169 with natural dyes, 142 Brush process, 98 Brushes used in dyeing, 100 Butter, 60, 63 Cage, 80 Cageing, SO Campeachy wood, 133 Caracul, 8, 12 dressing of, 53 152 187 INDEX Caracul, dyeing of, 140 Carnivorous animals, furs of, 37 Cased skins, 3(5 Castor oil, 60, 03 Cat, civet, 5, S house, S Caustic soda, 44, 110. 113 Centrifugal machine, 40 Chamber drying. 73 Chamois dressing, 31 tan, 49,' oS, 61 Characteristics of tans, 65 Chestnut extract, 133 Chinchilla, 5, 6, 8. 94 blending of, 91, 104 Chinchillone, 9 China goat, black 'on, 141 Chlorates, 147 Chloride of lime, 174 bleach, 1S4 Cln-ome acetate, 120 alum, 57, 120 colors, 176 copper mordant, 167 formaldehyde tan, 64 tans, 57, 174 Chromimn mordants, 120, 166 - — — alkaline, 123 salts in tanning, 53 Cleaning pelts, 40 Coal tar colors, 171 Cocoa nut oil, 60 Cod-liver oil, 60 Collagen, 25 Colloidal solutions, 4S Combination tans, 49, 64 Conveying dyed skins, 104 Conveyor drying. 73 Copper acetate. 119 mordants, 119, 166 salts, 109 after-treatment with, 16S sulphate, 119 Copperas, 119 Copper-iron mordant, 167 Coriin, 21 Corium, 21 Cortex, 23 Cottonseed oil, 60, 63 Cuba wood, 134 Cutch, gambler, 65, 135 Cuticle, 23 Davy, Sir Humphrey, 47 Degreasing furs, 179 Diphenyl black, 152 Dip process, 98 Dressing of lambs, 52 rabbits, 54 moles, 54 Drum, 80 Drum-cleaning, 105 Drumming, 76 Drying-oils, 60 Drying skins, 71 Durability of furs, 5 Dyeing furs at higher temperatures, 174 Dyeing of imitations, 93 novelty shades, 92 with aniline black, 144 coal tar colors, 171 mineral colors, 125 oxidation colors, 155 vegetable colors, 128 Egg-yolk, 63 Emeraldine, 145 Enzymes, 51 Epidermis, 21 Erdmann, 155 Ermine, 5, 9 bleaching of, 179 Fahrion, 48 Fat-glands, 21 Fats, animal, 59 Fermentation, 51 Ferrous acetate, 119 Ferrous sulphate, 119 Finishing dyed furs, 104 Fisher, 9 Fitch, 9, 94 Flat skins, 36 Fleshing, 41 knife, 38, 42 machines, 42 Flesh side, 22, 37 Formaldehyde, 63 chrome tan, 64 tans, 49, 63 Formic acid, 44, 50 as soaking agent, 39 Fox, black on, 140 188 INDEX blue, 9 cross, 4, 10 grey, 10 kit, 10 red, 4, 5, 10 dyed imitation silver fox, 137 silver, 4, 10 imitations, 137, 143 white, 11, 94 bleaching of, 179 French seal dye, 138, 144 Furamine dyes, 162 Fur beating machine, 80 Fur dressing, 30 Fur dyeing, 91 difficulties of, 95 with aniline black, 144 with coal tar colors, 171 with mineral colors, 125 with oxidation colors, 155 with vegetable colors, 128 Fur-hair, 24 Furriers' guilds, 34, 90 Furrol dyes, 166 Furs, colors of, 3 description of, 7 durability of, 5 of carnivorous animals, 37 of herbivorous animals, 37 quality of, 3, 4 uses of, 1 valuation of, 6 Aveight of, 5 Fustic, 134 — — • shades with, 135 Gallnuts, 128, 132 Gainbier cutch, 65, 135 Gelatine, 1, 25, 47, 48 Genet, 5 Glycerine, 63 Goat, 5, 11 logwood black on, 141 Green's process for aniline black, 152 Grey-Vjlue on white furs, 142 Ground water, 87 Guard-hair, 24 Guilds, furriers', 34, 90 Hair, 22 action of acids on, 27 action of alkalies on, 28 action of salts on, 28 Hamster, 3, 11 Hardness of water, 87 Hare, 5, 11, 94 black on, 140 blue-grey on, 142 lynx dye on, 1?6 stone marten imitation on, 126 Hematein, 133 Hematoxyhn, 133 Herbivorous animals, furs of, 37 Hudson seal, 144 Hydro-extraction, 40 Hydrogen peroxide, 168 bleaching with, 182 Hydrosulphite bleach, 181 Hypochlorites, 184 Imitations, dyeing of, 93 Iron mordants, 119, 167 Iron pyrolignite, 119 Iron salts in tanning, 53 Iron tan, 58 Iron vitriol, 119 Kangaroo, 12 Keratin, 25 Kicker, 61 Killing, 98, 106 ■ — — ■ formulas, 108 nature of, 107 purpose of, 106 by brush process. 111 by dip process. 111 with caustic soda, 113 ■ with lime, 112 with soda, 112 Knapp, 46, 57 Knife, beaming, 38 — shaving, 38 fleshing, 38 Kolinsky, 5, 12 Krimmer, 5, 12, 13 Lactic acid, 44, 51 Lactic acid fermentation, 50 Lambs, 12 dressing of, 50, 53 dyeing of, 92, 140, 141, 142 Lard, 60 Lead, acetate, 126 189 INDEX Lead sulphide dye, 126 Leather, definition of, 48 dressing of, 30 Leopard, 5, 13, 94 tanning of, 43 Lima wood, 135 Lime, 108, 110, 112 Linseed oil, 60 Litharge, 109 Loft drying, 72 Logwood, 133 blacks, 139 shades with, 134 Lynx, 5, 13 imitation on rabbit and hare, 126 Luster of hair, 23 Machines used in brush dyeing, 102 • dip dyeing, 103 Marmot, 14, 68, 94 Marten, blending of, 91, 104 Marten, baum, 5, 14 stone, 5, 14 - imitation, 126 Medulla, 22 Meunier, 46 Mineral colors, 125 oils, 59, 63 ■ tans, 49, 53 Mink, 5, 14, 68, 94 Mole, 5, 15 • tanning of, 54 Monkey, 15 Mordanting, 98, 114 Mordants, alkaline, 121 aluminum, 118 chrome-copper, 167 — • chromium, 120, 166 copper, 119, 166 copper-iron, 167 iron, 119, 167 tin, 121 Mucines, 25 Muskrat, 5, 15, 68, 94 imitation seal on, 144, 169 Neatsfoot oil, 60, 63 Neradol D., 64 Nigraniline, 147 Non-drying oils, 60, 63 Novelty shades, dyeing of, 92 Nutgalls, 33, 132 Nutria, 5, 15, 94 Oiling, 62, 77 Oils, drying, 60 non-drying, 50 partially-drying, 60, 63 OUve oil, 60 One-bath aniline black, 149 Opossum, 5, 15, 68 — — black on, 140 skunk imitation on, 138 seal imitation on, 144 Otter, River, 5, 16, 94 - — — Sea, 5, 16 Over-hair, 24 Oxidation aniline black, 150 — colors, 155 shades with, 165 Para-amido phenol, 153, 157 Para-phenvlene diamine, 153, 157, 162 Partially-drying oils, 60, 63 Pelage, 2 Pelt, 2 Pernambuco wood, 135 Peroxide of hydrogen, 168, 182 Peroxides, 182 Persian Iamb, 5, 12 dressing of, 50, 53 dj'eing of, 139 Physical theories of tanning, 47 Pickle, 49 Pigment granules, 23 Pony, Russian, 5, 16 Potassium permanganate as a dye, 127 — — as a bleach, 183 Protective-hair, 24 PyroUgnite of iron, 119 Quercitron, 135 Quinone di-imine, 163 Rabbit, 6, 17, 94 imitation seal on, 144 lynx imitation on, 126 • sable imitation on, 168 stone marten imitation on, 126 tanning of, 54, 65 Raccoon, 6, 17 190 INDEX black on, 140 skunk imitation on, 170 Rain water, 86 Red fox, dyed as silver fox, 137 Redwood, 135 Rodol colors, 165 Russian tan, 51 Sable, 6, 94 American, 17 blending of, 91, 104 imitation on rabbit, 168 Russian, 18 Salammoniac, 109 Salt, 32, 49 -acid tan, 49 water soak, 39 Salts, neutral, 54 basic, 54, 115 Sawdust in drum-cleaning, 80 "Schrot-beize," 50 Seal, 6, 18, 94 fur, 18 dyeing of, 92, 144 ■ hair, 19 imitation on muskrat, 138, 169 oil, 60 Shearing, 82 machine, 84 Shrinking-point of skins, 66 effect of chemicals on, 67 Silver fox imitations, 137, 143 Skin, 21 action of acids on, 26 action of alkalies on, 27 Skunk, 6, 19, 94 -imitation on opossum, 138 on raccoon, 170 Soaking sldns, 39 Soda ash, 110, 112 Sodium bichromate, 121, 166 bisulphite, 127, 181 chloride, 49 peroxide, 182 sulphite, 181 Soft water, 87 Softening skins, 38 Souring, 113 Squirrel, 6, 19 Staking, 78 Stannous chloride, 121 Stiasny, 64 Stone marten imitation, 126 Stretching, 78 machines, 78 Sugar of lead, 126 Sulphonated oils, 63 Sulphuric acid, 49 Sulphurous acid bleach, 180 Sumach, 128, 133 tanning with, 33 Surface water, 87 Sweat-glands, 22 Tallow, 60 Tanned furs, qualities of, 48 Tanning methods, comparison of, 65 Tannins, 32, 132 Tiger, 19 Top-hair, 24 Train oils, 63 Tramping machine, 61 Turmeric, 136 Under-hair, 24 Under-wool, 24 Ungreenable aniline black, 148 Unhairing, 82 machine, 83 Ursol dyes, 157, 165 Vanadium compounds, 147 Vat dyes, 177 Vegetable dyes, 128, 136 oils, 59* tans, 49, 65 Verdigris, 120 Water, hard, 87 soft, 87 Whale oil, 60 White fox, bleaching of, 179 Wolf, 6, 19 Wolverine, 6, 20 Wombat, 20 Wood dyes, 128 Yellow wood, 134 191 LITERATURE OF THE CHEMICAL INDUSTRIES On our shelves is the most complete stock of technical, industrial, engineering and scientific books in the United States. 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