Digitized by the Internet Archive 
 in 2018 with funding from 
 Getty Research Institute 
 
 https://archive.org/details/practiceofphotogOOdela_O 
 

 I 
 
PRACTICE OF PHOTOGRAPHY. 
 
t 
 
THE 
 
 PRACTICE OP PHOTOGRAPHY 
 
 A MANUAL 
 
 I’m iftnfants 
 
 BY 
 
 PHILIP H. DELAMOTTE, F.S.A. 
 
 ILLUSTRATED WITH 
 
 A CALOTYPE PORTRAIT TAKEN BY THE COLLODION PROCESS. 
 
 LONDON: 
 
 JOSEPH CUNDALL, 168 NEW BOND STREET. 
 
 1853. 
 

 
 ' 
 
 LONDON: 
 
 Printed by G. Barclay, Castle St. Leicester Sq. 
 
 
PREFACE. 
 
 Haying been frequently solicited by my friends and pupils 
 to supply them with brief instructions in the various Pho¬ 
 tographic Processes, I have prepared this little manual 
 on a simpler plan than any other treatise I have met 
 with, by endeavouring to carry the student directly 
 through the various stages of each process, without dis¬ 
 tracting his attention by untimely digressions on the 
 manufacture of chemicals or of apparatus—knowledge 
 very useful in its place, but a stumbling-block when ill- 
 timed. I have first described the Processes on Paper, 
 both for Negatives and Positives; then proceeding to 
 Glass, I have given in detail every information connected 
 with Collodion and Albumin, and I think everything 
 essential to the attainment of a good photograph will be 
 found mentioned. Amid the immense variety of formulae 
 
VI 
 
 PREFACE. 
 
 and methods recommended by different experimenters, I 
 have selected those which experience has assured me 
 are the best under all circumstances; but in an art of 
 such wonderfully rapid progress we must expect great 
 improvements daily: these shall find place in future 
 editions, should they be called for. 
 
 One feature in this work, which I hope will be 
 found useful, is the description of the various chemical 
 substances used in Photography: instead of being intro¬ 
 duced in the space devoted to the details of manipulation, 
 they are grouped together at the end: for these, and 
 for the general revision of the work, I am indebted to 
 the kindness of Mr. Thomas Delf, who undertook a task 
 which the numerous demands upon my time forbade 
 me fulfilling so carefully as the subject required. 
 
 P. H. D. 
 
CONTENTS. 
 
 NEGATIVES. 
 
 PAGE 
 
 Introduction . .1 
 
 On the Production of a Photographic Picture . . 4 
 
 Apparatus and Materials.• . 8 
 
 The Camera.9 
 
 The Tripod-Stand. . .12 
 
 Head-Bests.12 
 
 The Operating-Boom.13 
 
 Discovery of the Art of Photography.17 
 
 Processes on Paper. 
 
 The Dry Method . 21 
 
 Waxed-Paper Process. 
 
 Selection of Paper . 25 
 
 Preparation of the Waxed Paper . . . .27 
 
 Preparation of the Sensitive Paper . . . .30 
 
 Exciting the Iodised Paper.33 
 
 Exposure in the Camera.35 
 
 Developement of the Image . . . . . 40 
 
 Fixing the Negative Proof.42 
 
 The Wet Method.47 
 
 POSITIVES. 
 
 Preparation of Positive Paper.51 
 
 Positives on Albuminized Paper.54 
 
 Printing Process. 56 
 
yin 
 
 CONTENTS. 
 
 COLLODION PROCESS ON 
 
 GLASS. 
 
 
 Fixing the Positive Proofs 
 
 
 
 PAGE 
 
 . 58 
 
 Materials. 
 
 
 
 
 Chemicals. 
 
 
 
 . 64 
 
 Collodion Negatives .... 
 
 
 
 . 69 
 
 Immersion in a Bath of Nitrate of Silver 
 
 
 . 72 
 
 Exposure in the Camera 
 
 
 
 . 74 
 
 Developing. 
 
 
 
 
 Fixing the Proof .... 
 
 
 
 . 77 
 
 Conversion of Negatives into Positives 
 
 
 
 . 78 
 
 Positives on Collodion 
 
 
 
 . 83 
 
 Albumin on Glass .... 
 
 
 
 . 87 
 
 Chemicals used in Photography 
 
 
 
 . 93 
 
 “ Sizing” Materials .... 
 
 
 
 . 120 
 
 Definition of Technical Terms 
 
 
 
 . 123 
 
 Practical Hints. 
 
 
 
 . 127 
 
 Weights and Measures .... 
 
 
 
 . 130 
 
 APPENDIX. 
 
 Iodising the Paper .... 
 
 
 
 . 133 
 
 Exciting the Paper for the Camera 
 
 
 
 . 141 
 
 Exposure in the Camera 
 
 
 
 . 142 
 
 Bringing out the Picture 
 
 
 
 . 143 
 
 Fixing the Picture .... 
 
 
 
 . 143 
 
 The Printing Process .... 
 
 
 
 . 144 
 
 Various Methods.—Mr. Miller’s 
 
 
 
 . 145 
 
 Mr. Stewart’s . 
 
 
 
 . 146 
 
 Sir Wm. Newton’s 
 
 
 
 . 150 
 
 f 
 
INTRODUCTION. 
 
 Negatives. 
 
 (1.) Photography —a word derived from the Definition. 
 Greek—signifies “ to draw by the agency of light Photography 
 but as recent researches have proved that light is or 
 not the active agent through which the desired 
 effects are produced, the word Heliography, or Heliography. 
 “ sun-drawing,” has been suggested as the more 
 correct; yet, notwithstanding the inaccuracy in¬ 
 volved, it will be more convenient, for the purpose 
 of description, to retain the term “ Photography,” 
 and to assume that light is the agent by which 
 its results are obtained. 
 
 (2.) The art of Photography enables us to obtain Fixes the 
 
 i _. . . Images of 
 
 upon paper, and other media, permanent impressions the camera 
 of the images of objects which are received in the 
 focus of the camera obscura. 
 
 (3.) This wonderful result, which but a few Results 
 
 already 
 
 years since was regarded as a hopeless dream, has obtained, 
 been realised through the labours of Daguerre, 
 
 B 
 
2 
 
 INTRODUCTION. 
 
 Negatives. 
 
 The scientific 
 principles in¬ 
 volved must 
 be studied. 
 
 Talbot, Herschel, Hunt, and others engaged in 
 scientific investigations, and already attained to a 
 degree of perfection far outstripping the most san¬ 
 guine expectations. But rapid and wonderful as 
 have been its achievements, we think ourselves 
 justified in still regarding the art in its infancy, 
 for its processes and manipulation require a nicety 
 and delicacy unknown in any other art whatever; 
 while at the same time, the nature of the action 
 of the chemical and other agencies employed is 
 very imperfectly understood. We may, however, 
 congratulate ourselves that the art of photography 
 has now attained a satisfactory degree of simplicity 
 and certainty; and that scarcely a week passes 
 without some discovery being made which facilitates 
 its operations. 
 
 (4.) Although it is desirable, for many reasons, 
 to describe the practice of the art of photography 
 without entering upon the discussion of the scientific 
 principles involved, or the employment of techni¬ 
 calities, yet it must not be expected that while so 
 many refined considerations are involved in its 
 operations, success can always attend the efforts of 
 the photographer unless he pays to these principles 
 the obedience they demand: he must, sooner or 
 later, become acquainted with them. It is true 
 that any one entirely ignorant of the theory or 
 practice of chemistry may by a happy hit succeed 
 
INTRODUCTION. 
 
 3 
 
 Negatives. 
 
 at once in producing a good picture; but as he 
 knows not the causes of his success* or upon what it 
 depends* he may meet with an overwhelming amount 
 of discouraging failures without having the power to 
 remedy them* or to trace their origin. It is true 
 also* that patience and long-continued perseverance 
 may supply the want of this knowledge; but it 
 involves much loss of time and waste of materials. 
 Nevertheless it must be admitted that recent im¬ 
 provements have so simplified the processes of the 
 art* as to render chemical knowledge of much less 
 consequence than heretofore. Therefore it will be 
 our object in the following pages to present the details 
 of each operation in such a shape as will be clear 
 to the mind of any one entering upon the pursuit; 
 while* at the same time* the rationale of each 
 operation will be given in such form and language 
 as will enable the beginner to test his position at 
 every stage* and to trace and remove any impedi¬ 
 ments he may meet with. We do not propose to 
 give a history of the art* having now nothing to do 
 with past failures* but only with the successful results 
 of a multitude of experiments all tending to one aim* 
 
 —the greatest excellence and expedition in obtaining 
 good photographs. 
 
4 
 
 INTRODUCTION. 
 
 Negatives. 
 
 Upon what 
 the produc¬ 
 tion of a 
 photograph 
 depends. 
 
 The principal 
 Photo¬ 
 graphic agent 
 is Iodide of 
 Silver. 
 
 Preliminary 
 
 processes. 
 
 ON THE PRODUCTION OF A PHOTO¬ 
 GRAPHIC PICTURE. 
 
 (5.) The production of a photographic picture 
 depends upon the chemical action on various 
 substances of a certain power (Actinism), which 
 exists in the rays of light in connexion with two 
 other powers, viz. the luminous and the heating , 
 neither of which produces the same chemical change 
 upon the materials submitted to their influence in 
 the art of photography, as the actinic , or chemical 
 power does. It is not the object of our treatise to 
 enter upon this abstruse portion of the subject, we 
 must confine ourselves to the detailing of the best 
 manipulatory processes, with such explanation of 
 the scientific principles involved, as may enable the 
 amateur to practise the art with intelligence and 
 certainty. 
 
 (6.) The principal agent employed, after numer¬ 
 ous experiments upon other substances, still continues 
 to be iodide of silver, a compound of iodine with 
 silver; a substance highly susceptible of the 
 influence of light, which so acts upon, and alters the 
 normal condition of its particles, as to set up a new 
 action; and, by further accelerating this action, we 
 obtain the desired photographic pictures. Our 
 preliminary processes consist in:— 
 
INTRODUCTION. 
 
 5 
 
 Negatives. 
 
 (7.) I. In the paper process ,—Spreading upon On Paper, 
 paper a coating of one of the salts of iodine; the 
 iodide of potassium being that usually preferred. 
 
 Or, in the glass process ,— Coating a sheet of glass On Glass, 
 with iodised collodion, albumin, &c. 
 
 (8.) II. Bringing the surface of the prepared 
 paper, or collodion, into contact with a solution of 
 the nitrate of silver, by which decomposition ensues, Paper, &c. 
 and the iodide of silver is produced. The paper, or 
 other medium, is now ready for the camera. 
 
 (9.) III. Exposing the paper, or other medium, Rxposmgthe 
 in the Camera.—Upon being placed in the focus Camera - 
 of the camera, the varied, light of the image acts 
 unequally upon the prepared sensitive surface; and 
 according to the degree of illumination of the 
 various parts of the image, so the surface becomes, 
 in the subsequent processes, more or less darkened: 
 those parts which are most illuminated in the object, 
 producing the greatest amount of blackening effect 
 upon the sensitive surface. 
 
 (10.) IY. Developing the Image.—The paper, Develop^ 
 or other medium, after having been submitted to the Ima ge. 
 action of light in the camera does not exhibit any 
 of the change which has taken place upon its 
 surface: the picture is invisible, until the developing 
 agent is applied, which may be either gallic acid, 
 pyro-gallic acid, proto-sulphate, or proto-nitrate of 
 iron. This developing is a continuation of the action 
 excited by light. When the light strikes upon the 
 
6 
 
 INTRODUCTION. 
 
 Negatives. 
 
 sensitive medium, it reduces the iodide of silver to a 
 metallic state; and the chemical salts, gallic acid* 
 &c., do hut more rapidly perform the same change, 
 image the (H-) V. Fixing the Image.—This process 
 consists in carefully removing from the surface of 
 the medium all the iodide of silver, &c., which 
 has remained unacted upon by the light; this is 
 accomplished by immersing it in a solution of 
 hyposulphite of soda, which dissolves the unde¬ 
 composed iodide of silver that has not been acted 
 upon, and renders the picture no longer susceptible 
 of the action of light. 
 
 (12.) Such, briefly, are the successive operations 
 for obtaining a negative picture, which serves as a 
 type from which any given number of positives 
 Negatives on may be obtained. But negatives on glass may 
 inverted be also be converted into positives, as will be described 
 
 into posi¬ 
 tives. i n the proper place. 
 
 Theoper- (13.) The successful practice of the art of 
 
 ations of the v 7 x 
 
 wreouS? 11 ' photography requires on the part of the operator 
 andacmracy. the most scrupulous cleanliness and accuracy in 
 the employment of every material requisite to the 
 process, and the most implicit obedience to the 
 rules laid down in these pages for his guidance, 
 for they are the results of much patient investigation 
 on the part of a host of intelligent inquirers, who 
 have successfully overcome difficulties which, could 
 they have been foreseen, would have appalled the 
 
INTRODUCTION. 
 
 7 
 
 Negatives. 
 
 most patient and determined mind. Happily for 
 the photographer who now commences his career, 
 he can profit by this experience, and be spared 
 the labour and expense of original investigation. 
 
 The path for him is tolerably smooth, and should he 
 be induced to examine carefully the abstruse philoso¬ 
 phical principles upon which this fascinating art 
 depends, he may in his turn become a contributor to 
 its improvement and advancement. The humblest 
 experience may sometimes furnish a suggestion 
 which the most refined and cultivated investigator 
 may have failed to arrive at. 
 
APPARATUS AND MATERIALS. 
 
 Negatives. 
 
 Apparatus (14.) The apparatus and chemical materials em¬ 
 ployed must he selected with care and judgment. 
 The former need not be of the most expensive kind; 
 
 and ... . 
 
 all that is required is, that it should be capable of 
 fulfilling the conditions imposed upon it by the 
 Chemicals, requirements of the art. The chemicals must be 
 pure, such as are prepared especially for the purpose; 
 and to secure himself from disappointment and 
 failure, the operator should purchase them only of 
 respectable dealers in photographic materials, 
 var y mu ch (15.) Acetic acid, ether, and other preparations, 
 vary in quality, and an inferior article cannot be 
 substituted for one of the proper strength and purity. 
 
 (16.) Much of the time of early practitioners was 
 wasted in the preparation of various materials, but 
 now everything required may be bought, and in 
 Choice of, for a few hours a perfect equipment obtained. The 
 
 the various . 
 
 processes, choice of these must of course depend upon which 
 method of operating is adopted,—whether on plain 
 paper, waxed paper, or albuminized paper, or on 
 glass covered with albumin or collodion. For 
 operations out of doors, the waxed-paper process 
 possesses advantages over every other mode of 
 working, as little or nothing is required to be carried 
 besides the camera and the prepared wax-paper. 
 
APPARATUS AND MATERIALS. 
 
 9 
 
 Negatives. 
 
 THE CAMERA. 
 
 (17.) The choice of a camera will depend upon camera, 
 the purpose to which it is applied, whether for 
 portraits or landscapes; the sizes varying from 
 those of about five or six inches square to others 
 which will give a picture of twelve inches square 
 and upwards. The prices of cameras vary con¬ 
 siderably, according to the quality of the lenses; its Lenses, 
 as one with a single lens (meniscus) may be obtained 
 for a few shillings, while others, with two achromatic 
 lenses, manufactured by Voigtlander, Chevallier, 
 Lerebours, or Ross, are worth as many pounds. 
 
 As good pictures may probably be obtained with 
 one kind as with another; the advantage of the two¬ 
 fold achromatic arrangement is, that it concentrates 
 the light in the image, and thereby accelerates the 
 process, while it also gives that image tolerably free 
 from spherical and chromatic aberration. 
 
 (18.) For landscapes and views generally, one For Land- 
 lens, about three inches in diameter, of long focus, 1 
 say from twelve to eighteen inches, is the most 
 suitable. 
 
 (19.) For portraits, two achromatic lenses are For Portraits 
 necessary, each placed in a separate tube, one moving 
 within the other, for the purpose of adjustment. 
 
10 
 
 APPARATUS AND MATERIALS. 
 
 Negatives. 
 
 Foci in a 
 simple lens. 
 
 Achromatic. 
 
 Lens. 
 
 Construction 
 
 of; 
 
 Corrects 
 both spher¬ 
 ical and chro¬ 
 matic aber¬ 
 rations. 
 
 Aplanatic 
 
 Lens. 
 
 (20.) In a simple lens, that is, one composed of a 
 single piece of glass, there are two foci: the one, 
 where the image appears clearest and well defined— 
 this is termed its apparent focus; the other, which 
 is a little nearer to the lens, is the chemical focus, 
 or where the greatest amount of chemical action 
 takes place. 
 
 (21.) An achromatic lens is always composed of 
 two pieces of glass of different dispersive powers; that 
 is, the one has its chemical focus at a certain dis¬ 
 tance from the apparent focus; the other, also at a 
 certain distance, but a little nearer to, or farther 
 from, the apparent focus, according to its form. 
 
 (22.) One piece of the achromatic lens consists of 
 a double convex lens of crown glass; this disperses 
 the rays too much, to correct which defect we add 
 a concave lens of flint glass, which of itself would 
 cause the dispersion of the rays to be too little; but 
 these two lenses being put together, they correct 
 each other, and unite the rays at very nearly the 
 same point, making the chemical and apparent foci 
 identical. By giving the proper form to the surface 
 of these lenses a compound lens may be produced, 
 which shall correct not only this chromatic aberration, 
 but also the spherical aberration, or that which 
 produces distortion in the image of an object. A 
 lens which corrects both chromatic and spherical 
 aberration is said to be aplanatic. 
 
 (23.) It must always be borne in mind, that the 
 
APPAEATUS AND MATEEIALS. 
 
 11 
 
 Negatives. 
 
 nearer the lens is placed to the object to be copied, 
 
 the larger the image produced in the focus, and the 
 
 greater the distortion (68). In portraits, where great Lens for Por¬ 
 traits. 
 
 concentration of light, and consequent rapidity of 
 action, is desirable, a combination of lenses producing 
 a focus of five or six inches is the best; if the face is 
 formed as near as possible in the centre of the lenses, 
 the amount of distortion is so small as to be undis- 
 cernible; if any occurs in the accessories, it is of 
 less importance (67). 
 
 (24.) It is usual to place in front of the lens a disc Diaphragm, 
 of brass, perforated in the centre with a hole of given 
 diameter, capable of being removed to give place 
 to others of different diameters; these discs are 
 termed diaphragms , and their purpose is, to exclude 
 the excess of light falling upon the lens, which 
 would weaken the impression of the image; to 
 diminish the spherical aberration; and to give a 
 greater amount of distinctness to the image: but at 
 the same time they exclude much light, and thereby 
 lengthen the time of the operation; yet with lenses of 
 large diameter they are indispensable: the greater the 
 amount of light falling upon the object to be copied, 
 the smaller may be the aperture in the diaphragm. 
 
 (25.) Another disc, called a cap , is used for shut- Cap. 
 ting out entirely the light from the camera in taking 
 a picture, and stopping the operation at once. 
 
 (26.) The interior of the camera must be interior of 
 
 v ' Camera. 
 
 carefully blackened by being lined with paper. 
 
12 APPARATUS AND MATERIALS. 
 
 Negatives. 
 
 velvet* or painted; whatever the material used* 
 it must he deadened so as to reflect no light* but 
 absorb all the rays not falling upon the prepared 
 surface placed in the focus. 
 
 Adjustment (27.) Great care must be taken to test the 
 
 Focus. accuracy of the adjustment of the frames fitting into 
 the place of the ground glass* so that the prepared 
 surface falls exactly in the same place as that 
 occupied by it* when the focus is ascertained; any 
 deviation from which would cause distortion or 
 vagueness in the impression (67). 
 
 Tripod-stand (28.) The Tripod-stand. — In taking views the 
 camera should be elevated upon a tripod-stand* to a 
 height nearly equal to that of the eye of the operator. 
 
 (29.) In portraits* the lenses being of short focus* 
 very small projections from the object produce great 
 distortion in the image; it is* therefore* desirable to 
 keep the various parts of the object* as much as 
 possible* in the same plane: for this reason* if the 
 body is turned direct to the front of the lens* the 
 head should be turned on one side* so as to give the 
 face in three-quarter view* or nearly in profile. 
 
 Head-rest. (30.) Head-rests. — In taking portraits it is 
 advisable to place the head of the sitter against a 
 head-rest. This little instrument greatly assists 
 the keeping it in one position. Care must be taken 
 that no part of it is visible in the picture. 
 
OPERATING-ROOM. 
 
 13 
 
 THE OPERATING-ROOM. 
 
 (31.) Photography requires that its operations 
 should be conducted in a room from which the 
 daylight is either totally excluded, or admitted 
 through a transparent yellow medium, such as 
 stained glass, dyed linen, calico, coloured paper, or 
 similar material; or the room may be illuminated 
 by a candle or screened gas-light; for it must 
 always be kept in mind that it is through the agency 
 of light , and its peculiar action upon the chemicals we 
 use, that pictures are obtained; and whenever a 
 sensitive preparation is exposed, if but for an instant, 
 to its influence out of the camera, that change is in 
 operation to the deterioration of the picture. 
 Therefore, during every stage of progress in the 
 preparation of the sensitive surface until it is finally 
 fixed and rendered no longer susceptible of change 
 by the action of light, we must carefully guard 
 against any kind of exposure to its influence. A 
 disregard of this condition is undoubtedly the cause 
 of many failures which are attributed to other causes. 
 The operations of light are very subtile and mys¬ 
 terious : recent researches show us that it is con¬ 
 stantly changing the equilibrium of all bodies 
 exposed to its influence; its rays possess a compound 
 influence and agency; part of them give heat , part 
 
 Negatives. 
 
 Operating- 
 
 room. 
 
 Action of 
 Light. 
 
14 
 
 OPERATING-ROOM. 
 
 Negatives. 
 
 Actinism. 
 
 Closet 
 
 and 
 
 Sink. 
 
 light, and others a chemical action; or, as it is now 
 called; actinism . It must suffice for our purpose to 
 merely mention these; and remark that it is not by 
 the agency of the light rays alone that the photo¬ 
 graphic pictures are produced; at present it is 
 thought that the chemical or actinic rays are those 
 which set up the change in materials operated upon ; 
 still it is most convenient for the purposes of 
 description that we should continue to use the term 
 light as the agent by which our operations are 
 effected. 
 
 (32.) It is a great advantage to the photographer 
 if his operating room contains a closet in which the 
 materials can be put away out of the dust and 
 obnoxious vapours always present in the atmosphere, 
 and where he can suspend his sensitive papers while 
 they are drying. A sink, or similar convenience, 
 for the washings and other operations, and an abun¬ 
 dant supply of filtered water, is indispensable. 
 
PHOTOGRAPHY. 
 
PHOTOGRAPHY, 
 
 (33.) The discovery of the art of photography 
 is due to Mr. Fox Talbot, who* early in 1839, 
 communicated to the world the result of his experi¬ 
 ments, and an account of the processes by which 
 they were conducted.* This discovery was so start¬ 
 ling, and its capabilities so wonderful, that the whole 
 scientific world was interested in them, and directed 
 its attention to their developement; with what 
 result we need not inquire, for the evidence abounds 
 on every side. It is due, however, to the memory of 
 our distinguished countryman, Wedgwood, to state 
 that, so long back as 1802, he was engaged with 
 Sir Humphry Davy in attempting to fix the images 
 of the camera obscura. If he was unsuccessful, it 
 was probably due to the imperfect state of chemical 
 science at that period. 
 
 (34.) As Mr. Talbot patented his processes on 
 paper, much ingenuity was exerted to discover other 
 substances and other methods by which his results 
 * See Appendix, page 133. 
 
 Negatives. 
 
 Mr. Talbot’s 
 discovery. 
 
 C 
 
18 
 
 PHOTOGRAPHY. 
 
 Negatives. 
 
 Improve¬ 
 ments by 
 Herschel 
 and others. 
 
 Time re¬ 
 quired on 
 Paper and 
 Collodion. 
 
 Desirability 
 of perfecting 
 the paper 
 process. 
 
 By improve¬ 
 ment in de¬ 
 veloping. 
 
 could be attained; and the researches of Herschel, 
 Hunt, Archer, and others, have given us the cyano- 
 type, chromatype, amphitype, and the collodion 
 process, while, at the same time, they have greatly 
 improved the processes of Mr. Talbot himself. 
 
 (35.) These various improvements enable us 
 now to obtain good views, portraits, &c., on paper, 
 in a space of time varying from a few seconds to an 
 hour and a half; while on collodion and on albumin 
 instantaneous exposure to the image in the focus of 
 the lens is sufficient to obtain a good picture. 
 
 (36.) The negative pictures obtained on glass 
 appear to possess a slight advantage in clearness 
 and sharpness over those obtained on paper; but 
 there are so many advantages in using the latter 
 material, that all our skill should be directed to 
 perfecting it. Probably our efforts would best 
 be directed to the developing agents; the sensi¬ 
 tiveness of the iodide of silver perhaps cannot be 
 increased; and if, as is now supposed, the instan¬ 
 taneous action of light suffices to effect the change 
 in this substance necessary to the impressing the 
 image, it must result that it is only due to the 
 imperfection in the developing agent that instan¬ 
 taneous pictures cannot be obtained also upon paper. 
 
PROCESSES ON PAPER. 
 
PROCESSES ON PAPER. 
 
 (37.) The processes on paper are two,— the dry 
 and the wet; the former is the most convenient, and 
 that generally practised; by some practitioners the 
 latter is preferred: we shall here describe both 
 processes, beginning with — 
 
 (38.) The Dry Method. —This process is de¬ 
 serving of the most assiduous cultivation; for its 
 simplicity and ready manipulation give to it an ad¬ 
 vantage over all other methods; by it we can carry 
 a stock of prepared papers to any distance, and after 
 exposing them in the camera to the desired object, 
 reserve the further stages of the process until we 
 return to the conveniences of the operating-room. 
 Whatever imperfections now exist in this method, 
 and they are but few, will doubtless soon be over¬ 
 come : the results obtained at the hands of several 
 eminent photographers leave but little to desire; in 
 fact, in many positive proofs it is difficult, if not 
 
 Negatives. 
 Wet and dry 
 processes. 
 
 The dry pro¬ 
 cess. 
 
22 
 
 PROCESSES ON PAPER. 
 
 Negatives. 
 
 Paper em¬ 
 ployed. 
 
 The quality. 
 
 Proportions 
 of iodine and 
 silver. 
 
 impossible* to discover whether they have been 
 obtained from negatives on glass or on paper. 
 
 (39.) The paper used for the negatives can be 
 employed either waxed or unwaxed. As good 
 results are obtainable from the one as from the other; 
 the employment of the latter saves much trouble; 
 and the proofs can be rendered transparent by 
 waxing after they are developed. 
 
 (40.) The quality of the paper used is of vital 
 importance in this process; it must be as thin as 
 possible* but of perfectly homogeneous texture 
 throughout. 
 
 (41.) The proportions of iodide of potassium 
 and nitrate of silver in the solution employed differ 
 much in the practice of various photographers ; the 
 best result is most probably obtained when the 
 quantity of silver in the iodide of that metal is 
 in excess* for true iodide of silver (that is* when 
 these two bodies are combined in definite atomic 
 proportions) is not acted upon by light. 
 
 We now proceed to detail the processes with 
 waxed paper by the dry method. 
 
WAXED-PAPER PROCESS. 
 
WAXED-PAPER PROCESS. 
 
 1. Selection op Papee. 
 
 Negatives. 
 
 (42.) The early photographers encountered 
 great and discouraging difficulties in procuring 
 paper suitable for the purpose of their art, which 
 now no longer exist. Good papers are easily 
 obtained of various degrees of thickness, uniform paper - 
 texture, well-sized and glazed, both of English and 
 French manufacture; some prefer the former, others 
 the latter. The difference in their quality appears 
 to consist in this,—the English papers are hard and 
 dense, owing to their being sized with gelatine, 
 consequently the sensitive preparation does not 
 penetrate its substance, but remains on the surface. 
 
 They are, therefore, best fitted for positive proofs. For Positives 
 The French papers, on the contrary, are generally 
 sized with starch, with which iodine enters eagerly 
 into combination: they are usually thinner and 
 lighter, and consequently better adapted for nega¬ 
 tives; but both English and French papers are pre- 
 
 . n _ 1 r 1 ForNega- 
 
 pared for positives and negatives; and the photo- tives - 
 
26 
 
 PEOCESSES ON PAPEE. 
 
 Negatives. 
 
 Only one 
 quality of 
 paper to be 
 used. 
 
 Examine 
 each sheet 
 carefully for 
 defects. 
 
 grapher can select either without any reserve; only 
 with this precaution, let him avoid using different 
 papers as much as possible, for the difference in 
 their manufacture causes them to be affected differ¬ 
 ently under the same treatment. If bought of an 
 honourable dealer in apparatus, &c., there is little 
 fear of an unsuitable material being offered for sale. 
 All the success of manipulation may rest upon 
 the quality of the paper. 
 
 (43.) Previous to using the paper, each sheet 
 must be examined for spots and holes; if any such 
 exist that sheet must be rejected. The demand for a 
 fine material for the purposes of photography has 
 become so extensive, that several manufacturers have 
 devoted their attention to the preparation of a pure 
 paper, and the result is all a photographer can desire. 
 Among English manufacturers, Whatman, Nash, 
 and Turner, are eminent; Lacroix, and Canson, 
 freres, are the most eminent of those of France. 
 Lacroix’s paper appears to give the greatest rapidity, 
 doubtless owing to its containing the largest quantity 
 of starch. For waxing, thin paper will answer as 
 well as thick, if of homogeneous texture. 
 
WAXED-PAPER PROCESS. 
 
 27 
 
 PREPARATION OF THE WAXED PAPER. 
 
 (44.) Suitable waxed paper for photography 
 has only just become an article of commerce; the 
 preparation of it is troublesome* but worth sub¬ 
 mitting to from the great facilities it affords in 
 promptly obtaining pictures (negatives). The mode 
 of preparing it is as follows:—Take a daguerreo¬ 
 type plate* or polished steel or copper-plate* such 
 as are prepared for the use of engravers* but 
 larger than the paper to be waxed* and place it on 
 a stand so that a gas-burner can be passed under 
 and maintain it at a steady temperature; when 
 the plate is sufficiently warm* rub it all over with 
 a piece of clean white wax; then lay upon it 
 carefully a sheet of the thin negative paper* so 
 that no air-bubbles are formed* and as soon as it 
 is penetrated by the wax* cover it with another 
 sheet; have ready a second heated plate* upon which 
 put a sheet of the unwaxed paper* and place upon 
 it the two waxed sheets* cover them with a sheet or 
 two of unwaxed paper* and allow the excess of wax 
 to be absorbed by them* by which means any waste 
 of wax may be avoided; repeat this operation so 
 long as any excess of wax is absorbed by the clean 
 paper* and finally place it between several more 
 fresh sheets* upon the clean hot plate* and pass over 
 
 Negatives. 
 
 Waxing the 
 paper. 
 
28 
 
 PROCESSES ON PAPER. 
 
 Negatives. 
 
 Best kind of 
 paper for 
 waxing. 
 
 Quality of 
 paper im¬ 
 proved by 
 waxing. 
 
 them a hot smoothing-iron until the whole excess of 
 wax is removed. This operation is best performed 
 by two persons, one to each plate; as the wax cools 
 so rapidly when removed from the hot plate, much 
 time is wasted in the manipulation when performed 
 by a single person. The first plate being rewaxed, 
 the paper used for absorbing the excess of wax is 
 placed upon it, in order to become thoroughly 
 saturated, and then removed and treated as before 
 directed. The preparation of a hundred sheets in 
 this manner is a good day’s work. 
 
 (45.) The kind of paper best suited for waxing 
 is a very thin quality manufactured by Lacroix, 
 and Canson, freres: it contains a large quantity of 
 starch, which increases its sensitiveness. 
 
 (46.) This waxed paper possesses some excellent 
 qualities, which render it exceedingly valuable to the 
 photographer. It is transparent, which enables him 
 to perceive the smallest bubble of air that exists 
 between it and the exciting solution upon which 
 it is floated: it has become exceedingly tenacious, 
 somewhat resembling vellum; and it will admit of 
 a proof being left in the developing solution for a 
 considerable time, without spotting or staining the 
 solution; but, above all, it permits us to prepare 
 sensitive paper with the nitrate of silver, and keep 
 it ready for use during many days, weeks, or even 
 months. This quality is of immense value for 
 operations out-of-doors, since it is no longer neces- 
 
WAXED-PAPER PROCESS. 
 
 29 
 
 Negatives. 
 
 sary to carry a cumbrous and fragile array of 
 bottles and dishes; a portfolio and a camera suffice 
 for a long journey. The waxing also enables us to 
 obtain much deeper blacks upon thin paper than 
 we could were it not employed. 
 
 For the benefit of those who have not much 
 time to spare, we may remark that waxed paper is 
 now extensively prepared for sale, and may be 
 obtained of most of the respectable dealers in photo¬ 
 graphic materials. 
 
30 
 
 PEOCESSES ON PAPEE. 
 
 Negatives. 
 
 Use of starch 
 in the pre¬ 
 paration of 
 sensitive 
 paper. 
 
 Eice-starch. 
 
 PREPARATION OF THE SENSITIVE 
 PAPER. 
 
 (47.) To increase the sensitiveness of paper for 
 photographic purposes* it is found useful to prepare 
 it with a coating of some organic substances* which 
 act upon the nitrate of silver with energy* and 
 render it almost black. For this purpose* the 
 French chemists have suggested sugar of milk and 
 starch (175); this latter has the additional recom¬ 
 mendation of entering into combination with iodine. 
 
 (48.) Starch exists in many vegetable grains* 
 roots* &c.: the best for the purposes of photo¬ 
 graphy is obtained from rice. To prepare it* take 
 
 Distilled water.3 pints 
 
 Washed rice.4 ounces 
 
 Isinglass*. \ ounce. 
 
 Boil them in a glass or porcelain vessel* and filter 
 
 through a clean cloth. The boiling must only be 
 continued so long as the grains of rice begin to 
 break* and stopped before the water is thickened by 
 excess of starch. This liquid* to which the follow¬ 
 ing ingredients are added* gives a good body to 
 
 * Genuine isinglass is required—not the spurious substitute, 
 gelatine . 
 
WAXED-PAPER PROCESS. 
 
 31 
 
 Negatives. 
 
 paper, and yields very excellent tones of black in 
 the proofs. 
 
 Dissolve in one quart of this rice-water. Formula for 
 
 x J the sensitive 
 
 preparation. 
 
 Sugar of milk. 693 grains 
 
 Iodide of potassium . . . 230 „ 
 
 Cyanide of potassium . . 12 „ 
 
 Fluoride of potassium . . 6 „ 
 
 (49.) When these are dissolved, filter through a 
 fine cloth, and preserve the liquid for use in a well- 
 closed bottle: it will keep for a long time without 
 deterioration. In cold weather, it should be made 
 tepid before using. 
 
 (50.) To render the paper sensitive, put a^mgthe 
 quantity of the solution into a clean porcelain dish, 
 and immerse in it the sheets of paper, one by one, re¬ 
 moving the bubbles of air between each. As many 
 as twenty sheets of paper may be prepared at one 
 time, provided the liquid completely covers them: 
 they should be left in the liquid from half an hour 
 to an hour, according to the thickness of the paper. 
 
 (51.) When the waxed paper is placed in the 
 bath of iodide of potassium, that salt appears to 
 completely penetrate the wax and enter into com¬ 
 bination with it; the greasiness of surface disap¬ 
 pears, and the paper takes freely the solution of 
 nitrate of silver. This action, however, does not 
 take place immediately, but during the space of 
 half an hour, or an hour, before the wax becomes 
 decomposed. 
 
32 
 
 PROCESSES ON PAPER. 
 
 (52.) At the expiration of that time, take np the 
 mass of paper, and turn it so that the sheets which 
 were lowest become uppermost; then hang them up 
 separately by one corner to drain, and to the bot¬ 
 tom of each sheet attach a piece of blotting-paper to 
 facilitate the dropping of the fluid, 
 kind ofpaper (53.) Two different kinds of paper should not be 
 th e b same d m placed at one time in the bath. Paper sized with 
 this fluid has a light violet tint, which is not 
 objectionable, but, on the contrary, is useful in the 
 subsequent operation, as it serves to show when the 
 action of the nitrate of silver upon the iodide is 
 completed. 
 
 (54.) Paper thus prepared is said to be iodized 
 and insensible to the action of light, but too much 
 exposure decomposes the iodide of potassium, and 
 precipitates the iodine upon the starch. 
 
 (55.) The liquid will serve for fresh paper as 
 long as it lasts, taking the precaution to filter it 
 after use. 
 
 (56.) Starch, insoluble in cold water, dissolves 
 completely in boiling water; after it becomes dry, 
 it is again insoluble in cold water. Advantage is 
 taken of this property to apply it to paper, as 
 above directed. 
 
 (57.) This preliminary preparation is applicable 
 to paper for negatives, whether it is used waxed 
 or otherwise. 
 
WAXED-PAPER PROCESS. 
 
 33 
 
 EXCITING THE IODISED PAPER. 
 
 (58.) Have ready two or three porcelain or 
 gutta-percha dishes* of a size sufficiently large to 
 contain the paper; fill one with distilled water* into 
 the other put the following mixture*— 
 
 Distilled water ..... 1 oz. 
 
 Nitrate of silver.30 grains 
 
 Glacial acetic acid .... 35 „ 
 
 The acetic acid to he added after the nitrate of silver 
 is dissolved. 
 
 (59.) The iodised paper is to be taken carefully 
 by its opposite corners* and laid dexterously upon 
 the surface of the fluid in the dish* and all bubbles of 
 air removed; let it remain about five minutes* or 
 until the- surface which was tinted with the iodine 
 has become white by the action of the nitrate of 
 silver; then remove the paper to the dish of 
 distilled water, and immerse until the water con¬ 
 tains all the sheets submitted to the action of the 
 silver. If the paper is not required for immediate 
 use* it should be washed in another portion of dis¬ 
 tilled water. The water used in these washings 
 contains a quantity of nitrate of silver* and should 
 not be thrown away* but preserved for a subse¬ 
 quent operation—the Developing* which will be 
 explained hereafter. 
 
 (60.) After the washing* each sheet of paper 
 
 D 
 
 Negatives. 
 
 Production 
 of the iodid 
 of silver. 
 
34 
 
 PROCESSES ON PAPER. 
 
 IN RjljATI V JLO. # IP 
 
 must be drained for a few moments, and afterwards 
 dried between folds of blotting-paper, and preserved 
 in a portfolio out of the light. The whole of this 
 operation above described must be performed by 
 candle-light. 
 
 To prevent (61.) Unless the paper is washed once or twice 
 
 the paper y L x 
 
 discoloured * n dialled water, it is nearly certain to become 
 stained, even when kept in a portfolio, out of the 
 reach of daylight. This discoloration is caused by 
 the undecomposed nitrate of silver: there is no 
 danger of removing the sensitive iodide of silver by 
 the repeated washings, unless the surface is rubbed, 
 as that salt is insoluble in water; the nitrate, on the 
 contrary, being soluble, is removed by the action of 
 the water. 
 
 (62.) The operator must be careful not to touch 
 any part of the paper with his fingers, except the 
 corners by which it is held. 
 
 (63.) This paper will retain its sensitiveness for 
 three or four weeks, or even more, if carefully pre¬ 
 pared ; hence it becomes exceedingly valuable to 
 the traveller, as it enables him to dispense with 
 many delicate manipulations which are performed 
 with difficulty out-of-doors; and the “developing” 
 may be deferred until it can be practised in-doors. 
 
WAXED-PAPER PROCESS. 
 
 35 
 
 EXPOSURE IN THE CAMERA. 
 
 (64.) In selecting a view for a photographic 
 picture, much care, taste, and skill, should be ex¬ 
 ercised ; and in the hands of one who possesses an 
 artistic feeling, the results are often truly wonder¬ 
 ful. In varying the attitude in a portrait, or point 
 of view in an architectural subject, or a landscape, 
 the artist will select such as are most conducive 
 to picturesque treatment, equally avoiding large 
 masses of strong sunlight or deep shadows. A sky 
 in which the sun is obscured by large white clouds 
 is the most favourable. Violent contrasts of light 
 and shade are not suitable for photographic views; 
 they give a heavy, blotty appearance, the contrast 
 between the lights and the shadows being too power¬ 
 ful. It is only in the hands of a true artist, or man 
 of taste, that pleasing results may be looked for. 
 He who proceeds mechanically in his task may, by 
 a fortunate accident, produce a good picture; and 
 we have abundant evidence to show us that the 
 mechanical treatment of nature is the most com¬ 
 mon and the least successful. It is in the hands 
 of artists that photography will attain its highest 
 excellence, to whom the attainment of effect is intui¬ 
 tive, while they themselves will acquire much valu¬ 
 able instruction from studying its results. Not- 
 
 Negatives. 
 
 Exposure in 
 the Camera. 
 
 Selection of 
 view. 
 
 Violent con¬ 
 trasts to be 
 avoided. 
 
 Artistic 
 treatment 
 required to 
 produce a 
 good result. 
 
36 
 
 PBOCESSES ON PAPEE. 
 
 Negatives. 
 
 withstanding the microscopic accuracy of detail 
 presented in a good photograph, its chief value 
 and excellence will be found to consist in its sacri¬ 
 ficing certain details, and in its representing masses 
 of light and shade, the more striking and curious 
 from being devoid of colour. In this country, at 
 present, the value of these productions, in an 
 artistic point of view, is scarcely recognised; while 
 in France, Italy, Germany, and America, they have 
 long ago occupied the portfolio of the cognoscenti 
 and the atelier of the student in art. 
 
 Near objects (65.) If the view selected to be taken consists 
 
 must be in v 
 
 the same 0 f ne ar objects, such a position should be chosen as 
 
 vertical plane J 1 
 
 will present all the objects included in the view as 
 nearly as possible in the same vertical plane; for 
 if the focus of the lens is adjusted to a distant 
 object, the near ones will be confused and distorted. 
 With distant objects, and a lens of long focus, this 
 defect is diminished. 
 
 Regard must (66.) The colours of the objects in the view 
 
 be had to the v 
 
 objects ° f mus t be taken into consideration, — remarking, that 
 blue, white, and such light colours, operate more 
 upon the sensitive surface than green, red, or yel¬ 
 low : if violent contrasts of these colours present 
 themselves unfavourably, the point of view should 
 be changed. 
 
 Sensitive (67.) The focus carefully adjusted, it only re¬ 
 paper must ^ J J 
 
 the P exact ^ ma ^ ns to place the sensitive-paper in exactly the 
 
 focus * same place occupied by the ground-glass upon 
 
WAXED-PAPER PROCESS. 
 
 37 
 
 Negatives. 
 
 which the image was received. When this is once 
 correctly ascertained* no further concern need be 
 taken respecting it. We only mention it* because 
 in some cameras* “ made to sell*” no care is taken 
 to adjust this plane. The interior of the camera 
 should be kept scrupulously clean* any particles of 
 dust in it carefully wiped out; the lenses* also* 
 should be wiped with a piece of wash-leather* and 
 the camera placed in “ position ” before a picture is 
 taken* so that its temperature may become uniform 
 with that of the surrounding medium. If it should Temperature 
 
 ° of the Camera 
 
 happen to be colder than the atmosphere* a deposit ize^withthe 
 of moisture may form upon the lenses and glass of atmos t )here - 
 the frames* by which a complete obscuration of the 
 image would occur. 
 
 (68.) The lenses of the camera are placed at Lenses, 
 the extremities of two tubes* traversing within each 
 other* for the purpose of adjustment of the focus. 
 
 Two lenses, each of long focus, when placed toge- Lenses, 
 
 ° ± o single or two- 
 
 ther* or nearly so* produce an image at a shorter ^f rrange ‘ 
 focus than either would separately, and with a 
 greater concentration of light at the focus* but of 
 smaller dimensions: this property renders the em¬ 
 ployment of two lenses favourable for taking por¬ 
 traits. For landscapes and views* a single lens* 
 either compound ( achromatic ) or simple* is generally 
 preferred; for if there is less intensity of light* this 
 deficiency is compensated for by diminished spherical 
 aberration (21). 
 
38 
 
 PROCESSES ON PAPER. 
 
 Negatives. 
 
 Meniscus, 
 the best form 
 when only- 
 one is used. 
 
 Time of ex¬ 
 posure in the 
 Camera 
 governed by 
 various cir¬ 
 cumstances. 
 
 (69.) If the operator requires to take both por¬ 
 traits and views* it is more convenient to have two 
 cameras* one much smaller than the other: that for 
 portraits need not be larger than will admit of its 
 carrying a frame of 7 inches by 5* or thereabouts. 
 That for landscapes* &c.* may be 15 to 18 inches* 
 by 10 to 14* according to the power of the lens. 
 One set of lenses will do for both cameras* the 
 single lens for views* the twofold arrangement for 
 portraits: but with this precaution* whereas in 
 taking portraits the convex side of the lens is pre¬ 
 sented to the object; for views* the concave side 
 must be turned in that direction. 
 
 (70.) If the lens employed is a simple one of the 
 best form ( meniscus )* it will be necessary* after ad¬ 
 justing it to the apparent focus* to move the frame 
 that carries the ground-glass a little nearer to the 
 object* in order to place it in the chemical focus* 
 where the action on the sensitive paper takes place. 
 
 (71.) It is not possible to give any rules for the 
 length of time the prepared paper should remain 
 exposed to the action of light in the camera. This 
 exposure is governed by*— 
 
 1. The amount of light illuminating the object 
 
 taken. 
 
 2. The colour and distance of that object. 
 
 3. The degree of sensitiveness possessed by the 
 prepared paper. 
 
 4. The size of the aperture in the diaphragm. 
 
WAXED-PAPER PROCESS. 
 
 39 
 
 Negatives. 
 
 (72.) With paper prepared according to the 
 preceding formula, and a lens of twelve inches focal 
 length, and a diaphragm with an half-inch aper¬ 
 ture in front of it, one to two minutes, on a 
 bright, sunny day, will suffice; but on a dark, 
 gloomy day, seven to ten minutes may be requisite. 
 
 We are sanguine in our belief that photography on 
 paper will not stay its progress until it produces a 
 sensitive surface, and a developing agent, which 
 will give an image on an instant’s exposure. 
 
 (73.) With a double (twofold) lens, and paper 
 prepared as directed, a portrait may be obtained on 
 a clear, bright day, in thirty to sixty seconds. 
 
 (74.) After the paper has been exposed so long 
 as may seem necessary in the camera, it must be 
 removed to a dark chamber, to be submitted to the 
 developing agent; for as yet no impression is visible 
 upon its surface. To avoid disappointment, it will 
 be advisable, in commencing, to take two or three 
 proofs of the same view, with different degrees of 
 exposure in the camera. 
 
40 
 
 PROCESSES ON PAPER. 
 
 Negatives. 
 
 Developing 
 the pictures. 
 
 Test of the 
 time of ex¬ 
 posure. 
 
 DEVELOPEMENT OF THE IMAGE. 
 
 (75.) Take a clean dish, capable of containing 
 an inch in depth of fluids and pour into it sufficient 
 of the following solution to completely cover the 
 paper:— 
 
 Distilled water .... 1 pint 
 
 Gallic acid.20 grains 
 
 Silver solution* .... 1 oz. 
 
 (76.) Immerse the proof completely in this solu¬ 
 tion, and watch its progress at intervals: if the time 
 in the camera has been well considered, the deve- 
 lopement will take place in ten or fifteen minutes; 
 otherwise it may require many hours. As soon as 
 the image is fairly out, remove the proof to a porce¬ 
 lain or glass slab, and wash it freely, rubbing a 
 camel’s-hair pencil or the finger lightly over the 
 back of the proof, to remove any crystalline deposit 
 which might leave spots. It must then undergo the 
 “ fixing ” operation, which is effected by dissolving 
 out the unchanged Iodide of Silver by hyposulphite 
 of soda (164). 
 
 (77.) The appearance of a proof after develope- 
 ment will serve to guide the operator as to the 
 length of exposure in the camera. If the time has 
 
 * The water used for washing the sensitive paper before men- 
 • tioned (59). 
 
WAXED-PAPER PROCESS. 
 
 41 
 
 Negatives. 
 
 been too short* the appearance of objects in the 
 proof will be feeble and indistinct. If the exposure 
 has been too long* or the quantity of light admitted 
 into the camera too great* the whole proof will 
 become darkened* sometimes unequally; in which 
 case* the time of exposure for the next picture must 
 be abridged* or the aperture of the diaphragm 
 diminished. 
 
 (78.) If the time of exposure has been too short* 
 the defect may frequently be completely remedied 
 by leaving the proof in the developing-bath a longer 
 time. It would appear that an action is set up in 
 the iodide of silver the instant the rays of light fall 
 upon it; and could we but find a developing agent 
 that would act with sufficient energy* this instanta¬ 
 neous exposure in the camera with prepared paper 
 would be as effectual as it is with iodised collodion. 
 
 But the longer* within certain limits* the paper 
 remains in the camera* the quicker the developing 
 process can be performed. For instance* if one 
 sensitive paper is exposed in the camera twenty 
 seconds* and another fifteen minutes* the first will* 
 perhaps* require a day and night’s immersion in the 
 gallic acid developing solution* while the latter will 
 be fully developed in an hour. 
 
 (79.) The action of the gallic acid is accelerated 
 if the solution be warmed before the proof is im¬ 
 mersed in it. 
 
42 
 
 PROCESSES ON PAPER. 
 
 Negatives. 
 
 FIXING THE NEGATIVE PROOF. 
 
 Proof by he (80.) The object of this operation is to fix the 
 iodXof the impression on the paper, by removing the iodide 
 Hyposul- and other salts of silver. These are insoluble in 
 pinte of soda wa ter: we have, therefore, to seek a convenient 
 solvent,—one which will dissolve these salts of 
 silver, and at the same time not injure the impres¬ 
 sion already depicted on the paper. Nothing has 
 been found better adapted for this purpose than the 
 hyposulphite of soda (164). Take 
 
 Filtered rain or river water . . 1 pint 
 
 Hyposulphite of soda . . . . J ounce. 
 
 Fixing the Pour a sufficient quantity of this into a dish, and 
 
 Image. # . 
 
 immerse the proof in it, watching carefully the dis¬ 
 appearance of the iodide from its surface, which can 
 be ascertained by the disappearance of the yellow 
 tint. This will take from a half to three-quarters 
 of an hour, in some instances; but, with well-waxed 
 paper, ten to fifteen minutes will be found sufficient. 
 The change the proof undergoes in this operation is 
 quite marvellous ; the “ darks ” acquire an intensity, 
 and the “ lights ” a brilliancy, truly astonishing. 
 
 (81.) The hyposulphite solution should be fil¬ 
 tered after each proof has been fixed: it will serve 
 many times, but only one proof at a time should be 
 placed in it. 
 
WAXED-PAPER PROCESS. 
 
 43 
 
 (82.) The proof should next be placed in a dish 
 of clean water* and washed with a camel’s-hair 
 brush; and after being immersed for half an hour 
 or so* rinsed in several waters* and hung up to dry. 
 It is now unalterable in the light. 
 
 (83.) If the waxed paper loses its transparency* 
 and presents a mottled appearance* as it generally 
 does at this stage of progress* it must be held before 
 the fire until warmed* then placed between two 
 sheets of blotting-paper* and a warm smoothing- 
 iron passed over it. This will completely restore 
 its transparency. 
 
 Negatives. 
 
 To restore 
 the trans¬ 
 parency of 
 the proof. 
 
THE WET METHOD. 
 
THE WET METHOD.* 
 
 Negatives. 
 
 (84.) Tins can scarcely be carried on out-of- ^g Wetpro " 
 doors away from the resources of the operating- 
 room ; but where circumstances will admit of its 
 being employed, very fine results can be obtained. 
 
 The paper is prepared in the same manner as in the 
 dry process, and may be either waxed or unwaxed. 
 
 (85.) 1. Immerse the papers in the solution of 
 iodide of potassium. 
 
 (86.) 2. Float them upon the aceto-nitrate solu¬ 
 tion for about ten minutes. 
 
 (87.) Have ready a sheet of glass which fits 
 accurately to the frame of the camera, and lay upon 
 it a piece of smooth white blotting-paper, previously 
 dipped in clean water: this is to receive and to keep 
 moist the sheet of sensitive paper, which must be 
 carefully laid upon the blotting-paper, sensitive side 
 uppermost, of course; it is best to pour over the 
 blotting-paper a gentle stream of water, so as to float 
 the sensitive paper, and by carefully tilting the glass 
 
 See Appendix, page 147. 
 
48 
 
 PROCESSES ON PAPER. 
 
 Negatives. 
 
 plate, allow the excess of water to drain off. When 
 the water ceases to drop, the glass-plate, with the 
 sensitive paper, may he removed to the camera and 
 exposed to the image in the focus of the lens. 
 
 (88.) Some practitioners place this wet sensi¬ 
 tive paper between two plates of glass while in the 
 camera; but there is no necessity for so doing, while, 
 at the same time, there is risk of disturbing the true 
 focus. 
 
 (89.) 3. The necessary exposure in the camera 
 being completed, the views are to be developed by 
 the saturated solution of gallic acid, as described in 
 the dry method. 
 
 (90.) 4. The fixing is accomplished in the 
 ordinary manner, by the solution of hyposulphite 
 of soda, and the negative proof can then be waxed. 
 
 (91.) The action of light is much more rapid 
 upon the wet paper than upon the dry. 
 
POSITIVES. 
 
 THE PRINTING PROCESS. 
 
PREPARATION OF POSITIVE PAPER. 
 
 Positives. 
 
 (92.) The paper for positives must be selected ^fthe^aper 
 with the greatest care; every sheet containing holes 
 or spots should be rejected,. We give the prefer¬ 
 ence to a good thick English paper, not too highly 
 glazed. Cut it the required size, and make a pencil- 
 mark at the corner on the back. Then pour into 
 a clean porcelain dish the following solution :— 
 
 Distilled water.1 pint 
 
 Hydrochlorate of ammonia . 1 ounce. 
 
 Place a sheet of paper on the surface of the solution, 
 and float it carefully so that the back of the paper 
 does not become wetted. After a few seconds lift it 
 off, and, holding it up against the light, examine if 
 the whole surface is completely wetted: this result 
 is secured if the paper has previously been placed 
 between some sheets of clean damp blotting-paper, 
 which renders it more susceptible to the absorption 
 of the water when placed in contact with it. Leave 
 it on the solution three or four minutes; take it out. 
 
52 
 
 PROCESSES ON PAPER. 
 
 Positives. 
 
 Upon what 
 the various 
 tints of the 
 positives de¬ 
 pend. 
 
 let it drain until it ceases to drip, then dry by 
 pressing it between some leaves of blotting-paper on 
 a smooth table. 
 
 (93.) It is now impregnated with the hydrochlo¬ 
 rate of ammonia (161); the object of this prepara¬ 
 tion is to produce a chloride of silver, by decom¬ 
 posing the nitrate of that metal in the next stage of 
 the process, which must be performed by candle¬ 
 light. Have ready another dish, into which pour 
 sufficient of the following solution to cover the 
 bottom:— 
 
 Distilled water ... 1 ounce 
 
 Nitrate of silver ... 60 grains. 
 
 Place upon it a sheet of the paper prepared as above 
 directed, first rubbing it with a piece of blotting- 
 paper to remove any crystals of the hydrochlorate, 
 carefully avoiding to wet the back. The time 
 which it should be allowed to remain will depend 
 upon the tint required in the proof. A short time 
 will yield red tints; a longer, dark brown, violet, 
 or black tints. Hang up the paper by one corner 
 to drain, and when dry preserve it for use in a 
 portfolio, between leaves of blotting-paper. 
 
 (94.) Paper thus prepared will remain white 
 some six or eight days: after that time it generally 
 begins to turn brown. Paper submitted to the first 
 solution can be kept any length of time before being 
 submitted to the silver solution. The second part 
 
PROCESSES FOR POSITIVES. 
 
 53 
 
 of the operation should be performed the evening 
 before the paper is required for use. 
 
 (95.) A quicker mode of preparing this positive Dr. Taylor’s 
 paper is by coating it with the ammonio-nitrate of 
 silver* as suggested by Dr. Alfred Taylor* as fol¬ 
 lows :—Make a solution of nitrate of silver* of the 
 strength of thirty-five grains to the ounce of dis¬ 
 tilled water; add to it gradually* drop by drop* a 
 strong solution of ammonia* a copious precipitate 
 falls; continue to add the solution of ammonia 
 until this precipitate is just re-dissolved: the paper 
 is floated upon this solution as directed for the 
 other (92). 
 
54 
 
 PROCESSES ON PAPER. 
 
 Positives. 
 
 Albuminized 
 
 paper. 
 
 Formula for 
 first process. 
 
 POSITIVES ON ALBUMINIZED PAPER. 
 
 (96.) Albuminized Positive Paper.— Positive 
 proofs taken upon paper coated with a film of 
 albumin (143) attain a brilliancy of effect by a 
 softening of the glaring white of the lights* with a 
 transparency in the shadows* which cannot be 
 arrived at by any other means. They are defec¬ 
 tive only when the albumin is applied too thickly. 
 Take of 
 
 White of eggs.8 ounces 
 
 Distilled water.8 ounces 
 
 Dry salt.2 ounces. 
 
 Beat the whole together into a froth with a wooden 
 spoon or fork. Take the froth as it runs* and put it 
 into a basin; let it settle for twenty-four hours. 
 It is then fit for use. Pour sufficient quantity into 
 a dish* and float a sheet of paper upon it for three or 
 four minutes; hang it up to dry thoroughly; then 
 place it between two sheets of glazed paper* and pass 
 a smoothing-iron* moderately heated* over it: keep 
 in a portfolio for use. 
 
PROCESSES ON PAPER. 
 
 55 
 
 (97.) Paper thus prepared is excited by placing 
 the albuminized side upon a bath containing the 
 following solution:— 
 
 Distilled water ... 1 ounce 
 
 Nitrate of silver . . .120 grains. 
 
 Let it remain in contact about four or five minutes; 
 then hang it up to dry, and preserve it out of the 
 influence of light. 
 
 Positives. 
 Formula for 
 second pro¬ 
 cess. 
 
56 
 
 PROCESSES ON PAPER. 
 
 PRINTING PROCESS. 
 
 (98.) Positive Proofs. —To obtain a good posi¬ 
 tive proof is the aim and end of all our previous 
 operations. Success in this result demands that our 
 negative should be as perfect as possible. The pro¬ 
 cess has been called printing, perhaps as good and 
 as expressive a name for it as any other. The 
 printing apparatus consist of a frame fitted with 
 a thick plate glass, and a wooden back with screws, 
 capable of exerting considerable pressure to bring 
 the plates, or paper negative, in close contact. 
 
 (99.) Place the back of the negative proof upon 
 the plate of glass. Then lay upon it the positive 
 paper, the prepared side upon the face of the nega¬ 
 tive, and cover it with a piece of black velvet or 
 cloth: then shut down the wooden back, and turn 
 the frame up, and place it perpendicular to the sun’s 
 rays, or expose it to the diffused light of day. In 
 order to ascertain when it is sufficiently darkened, a 
 piece of the positive paper should be allowed to pro¬ 
 ject beyond the negative, and by watching the 
 changes in this, a tolerably safe conclusion may 
 be arrived at. 
 
 (100.) The intensity of the negative will, how¬ 
 ever, require to be taken into consideration. A 
 
PRINTING PROCESS. 
 
 57 
 
 Positives. 
 
 little practice soon enables the operator to work 
 with some degree of certainty. 
 
 (101.) In this climate, where sunlight cannot 
 often be reckoned upon, it becomes exceedingly 
 desirable that the positive paper should possess a 
 high degree of sensitiveness. That prepared with 
 the ammonio-nitrate of silver, as suggested by Dr. 
 
 Taylor, appears to be more sensitive than any other 
 we have employed (95). 
 
58 
 
 PROCESSES ON PAPER. 
 
 Positives. 
 
 FIXING THE POSITIVE PROOFS. 
 
 Fixing tlie 
 positives. 
 
 (102.) The proof thus developed requires to be 
 “ fixed.” This is accomplished by washing off the 
 undecomposed nitrate of silver with the following 
 solution, according to M. Le Gray’s formula:— 
 
 Filtered rain-water .... 1 pint 
 
 Hyposulphite of soda . . . . 3 oz. 
 
 (103.) In another vessel make a solution of 
 nitrate of silver, thirty grains to one ounce of water. 
 When it is dissolved, add a saturated solution of 
 chloride of sodium, which causes a white precipitate 
 to fall; carefully decant the liquid, and spread the 
 precipitate at the bottom of the vessel, and let it 
 blacken in the sun; then add it to the hyposulphite 
 solution, which dissolves it. The object of this addi¬ 
 tion is to make a new solution of the hyposulphite of 
 soda act as promptly in producing good “ blacks ” as 
 it would if old. Every proof washed hi the hypo¬ 
 sulphite solution contributes a quantity of chloride 
 of silver; therefore in course of time it becomes 
 strong and thick; it must not be filtered; but a 
 fresh supply of simple solution of hyposulphite 
 added, when, if allowed to repose, it will again 
 become clear. 
 
 (104.) The positive proof being placed in the 
 above mixture, will acquire almost any degree of 
 
PRINTING- PROCESS. 
 
 59 
 
 Positives. 
 
 dark tone that may be desired, from red-brown to Fixing the 
 violet or black. A little practice will make the 
 result easy and sure of attainment. The time re¬ 
 quired varies from one hour to three or four days. 
 
 (105.) Heating the hyposulphite solution will 
 accelerate the operation of fixing; but it is attended 
 with some risk, and where the proof is of value 
 should not be attempted. 
 
 (106.) When the proof has attained the tone 
 desired, remove it from the solution; place it on a 
 slab of porcelain or glass, and wash it repeatedly 
 until the paper is tasteless; the hyposulphite of 
 silver is intensely sweet, and the smallest quantity 
 may be detected by the tongue. Hang the proofs 
 by one corner to drain, and then dry them be¬ 
 tween folds of blotting-paper. 
 
 If the positives have not been taken upon albu- 
 minised paper, they can now be washed with a 
 mixture of equal parts of white of egg and distilled 
 water, applied with a flat camel’s-hair brush. When 
 dry, place them between two pieces of glazed paper, 
 and pass a hot smoothing-iron over, which will 
 render the albumin insoluble. 
 
 The rich dark violet tint, so much admired in 
 many French pictures, is derived from the use of 
 sel d’or, or hyposulphite of gold (151). Make a 
 bath of 
 
 Distilled water .... 2 ounces 
 Sel d’or .1 grain ; 
 
60 
 
 PRINTING PROCESS. 
 
 Positives* 
 
 immerse the proof therein, keeping it moving 
 about, and as soon as the desired tint is obtained 
 remove it, and let a stream of water flow over it, 
 until the proof is perfectly freed from the undecom¬ 
 posed salt. 
 
 The solution of gold is precipitated upon the 
 salt of silver reduced by the action of light, while 
 the parts unacted upon remain intact. 
 
COLLODION PROCESS ON GLASS. 
 

 
 
 
COLLODION PROCESS. 
 
 (107.) MATERIALS. 
 
 Plates of Glass to fit the slide of the camera. 
 A pure white glass has lately been manufac¬ 
 tured for photographers, which will be found to 
 possess many advantages. The glass plates must 
 be perfectly flat, without scratches or air-bubbles. 
 Beginners who buy large cameras are advised to 
 purchase frames fitting into the slides which will 
 carry smaller plates of glass: as they are more 
 easily operated with, and less collodion is spoiled. 
 
 Bath of Gutta Percha or of Glass, to contain 
 the nitrate of silver solution, in which the glass 
 plates are plunged. The bath must be a little 
 larger than the plates. 
 
 Glass Dipper, with which to hold the glass 
 plate when dipped into the bath. 
 
 A large Dish, or Sink, over which the wash¬ 
 ing operations may be performed. 
 
 Levelling Stand, on which to lay the glass 
 plate during some of the operations. 
 
64 
 
 MATERIALS AND CHEMICALS 
 
 A Pair of Glass Scales, with grain, scruple, 
 and drachm weights, with which to weigh the 
 chemicals. 
 
 Glass Measures, graduated to 3 oz. or more, 
 to measure the quantities of water, &c. 
 
 Glass Measures, small, with which to pour on 
 the developing mixture. 
 
 Glass Rods, to stir the various mixtures. 
 
 Glass Funnels, for filtering. 
 
 Blotting Paper, prepared, for do. 
 
 Plate Boxes of different sizes, in which to 
 deposit the various-sized plates when the images 
 are fixed. 
 
 (108.) CHEMICALS. 
 
 Collodion, Iodised.— A four-ounce bottle will 
 suffice for many experiments. It is advisable to 
 have also a wide-mouthed one-ounce phial for con¬ 
 stant use—replenishing this from the larger bottle. 
 
 Nitrate of Silver.— Six ounces of crystallised 
 nitrate of silver will suffice for many experiments. 
 
 Glacial Acetic Acid.—A bottle holding three 
 ounces will suffice. 
 
 Pyrogallic Acid.— Six drachms. 
 
 Hyposulphite of Soda.—H alf a pound. 
 
 Ether.— Two ounces. 
 
 Nitric Acid.— One drachm. 
 
 Distilled Water. — A two-gallon bottle. 
 
USED IN THE COLLODION PROCESS. 
 
 65 
 
 And for variations of the Collodion process :— 
 
 Sulphuric Acid. 
 
 Proto-sulphate of Iron. 
 
 Sulphate of Per-oxide of Iron. 
 
 Bromide of Potassium. 
 
 Nitrate of Baryta. 
 
 F 
 
COLLODION NEGATIVES ON GLASS. 
 
COLLODION PROCESS. 
 
 NEGATIVES ON GLASS. 
 
 (109.) Collodion is gun-cotton dissolved in 
 etlier; to which alcohol is added (155). When 
 poured upon a plate of glass it runs freely over the 
 surface, and the ether and alcohol evaporating, leave 
 the collodion behind in the state of a tough trans¬ 
 parent film, which being prepared with the salts of 
 silver, photographic proofs can be taken upon it. 
 In Section 155 we have given the process for pre¬ 
 paring the iodised collodion, but it will usually be 
 found more convenient to buy it ready prepared. 
 By the use of this liquid we are now enabled to 
 obtain the impression of an image by one instant’s 
 exposure to the light. 
 
 (110.) The first important operation in the col¬ 
 lodion process is cleaning the glass plate. After 
 all traces of impurity are removed from the surface, 
 by washing it well in water, it is advisable to take 
 
 Collodion 
 Negatives 
 on Glass. 
 
 Cleaning the 
 glass plate. 
 
70 
 
 PROCESSES ON GLASS. 
 
 Negatives 
 
 on 
 
 Collodion. 
 
 Coating the 
 plate. 
 
 a small quantity of diluted ammonia and Tripoli 
 powder— 
 
 Filtered water.3 oz. 
 
 Ammonia solution ..... 1 drachm 
 
 Tripoli powder.1 scruple, 
 
 and rub it carefully over every part, including the 
 edges. The plate must then be washed and dried 
 with clean linen cloths, and kept free from dust 
 until the next operation, which is— 
 
 (111.) Coating the Plate with Collodion .—Having 
 arranged everything ready for use, fill a one-ounce 
 vial with iodised collodion,—and holding the glass 
 plate by the thumb and finger of the left hand, 
 pour out upon the glass at the part nearest the 
 thumb a gentle stream of collodion; incline the 
 plate dexterously, so that by one turn of the hand 
 the fluid may flow evenly over the plate gradually 
 down to the lower edge, with the exception of about 
 half an inch by which the plate is held, in this and 
 subsequent manipulations, and then, by depressing 
 the lower corner, the surplus collodion may be 
 poured back into the bottle.* This operation re¬ 
 quires some dexterity, and can be best acquired by 
 observing a skilful person perform it; then it be¬ 
 comes easy. When well performed the film of col¬ 
 lodion is perfectly smooth, free from bubbles and 
 
 * This operation may be performed by daylight, but 
 all further manipulations must be in the darkened chamber. 
 
COLLODION NEGATIVES ON GLASS. 
 
 71 
 
 ripples or streaks; before it becomes dry it must 
 be made sensitive by being submitted to the next 
 operation. 
 
 (112.) Some precautions are necessary to be 
 observed in the use of collodion, particularly that 
 no pieces of dry collodion, which are apt to form 
 round the neck and stopper of the bottle in which it 
 is kept, fall into the fluid, as if any of them pass 
 out on the glass plate they would produce streaks, 
 and inevitably spoil the picture. The deposit which 
 sometimes forms at the bottom of the reserve bottle 
 should not be disturbed while pouring the fluid 
 into the smaller one, as it, also, would destroy the 
 proof. 
 
 (113.) The plate must not be immersed in the 
 silver solution until it becomes tenacious, or set 
 The time at which this takes place varies with the 
 season and temperature of the place where the 
 operation is carried on. Usually the film of collo¬ 
 dion becomes opaque all over the plate: when this 
 change is effected, it may then be immersed in the 
 nitrate-of-silver bath. 
 
 Negatives 
 
 on 
 
 Collodion. 
 
72 
 
 PROCESSES ON GLASS. 
 
 Negatives 
 
 on 
 
 Collodion. 
 
 IMMERSION IN A BATH OF NITRATE 
 OF SILVER. 
 
 (114.) This bath is composed in the propor¬ 
 tions of— 
 
 Nitrate of silver ... 30 grains 
 Distilled water ... 1 oz. 
 
 and must be filled so as nearly to cover the glass 
 plate when it is dipped in. The solution must be 
 filtered through blotting-paper, and when not in use 
 kept in a glass-stoppered bottle out of the light. 
 The action of the solution-of-silver bath is somewhat 
 irregular, owing to various causes : if the tempera¬ 
 ture of the liquid is below 60° or thereabouts, it 
 frequently fails to form the iodide of silver. To 
 remedy this defect the bath should be kept in a 
 room where a fire is burning; or the bath may be 
 immersed in warm water for a few minutes before 
 it is required to be used. 
 
 (115.) When a fresh solution is first used in the 
 bath, it sometimes attacks the film of collodion, dis¬ 
 solves it, and pieces will be found floating about in 
 the liquid, which must be immediately filtered. A 
 bath that has been some time in use is usually found 
 to act better than one newly made: various remedies 
 have been suggested, such as the addition of a few 
 drops of nitric acid, or of iodide of potassium, allow- 
 
COLLODION NEGATIVES ON GLASS. 
 
 73 
 
 ing the fluid to re-dissolve the iodide of silver preci¬ 
 pitated* and filter. Take the glass plate coated 
 with collodion* lay it with its back upon a glass 
 dipper* and at one motion plunge it into the bath* 
 with the exception of about half an inch* by which 
 the plate is held* in this and subsequent manipu¬ 
 lations. Should there be any hesitation or delay* a 
 line will certainly be formed across the collodion* 
 which will render the plate useless. The plate 
 should be allowed to remain in the bath about two 
 minutes* to effect a combination between the iodine 
 and the silver; it should then be quickly raised out 
 of the bath* and dipped back again two or three 
 times. This helps to get rid of a certain greasy 
 appearance. The plate is then taken out* allowed 
 to drain for half a minute* and then shut up in the 
 camera-slide* and immediately taken to the camera. 
 If* however* it is necessary to carry the prepared 
 plate to a considerable distance* it is advantageous 
 to cover the film of collodion with another clean 
 plate of glass* which will prevent the moisture 
 evaporating; it is necessary* however* to have a 
 slide capable of holding both glasses* prepared 
 expressly for this purpose. 
 
 Negatives 
 
 on 
 
 Collodion. 
 
74 
 
 COLLODION NEGATIVES ON GLASS. 
 
 Negatives 
 
 on 
 
 Collodion. 
 
 EXPOSURE IN THE CAMERA. 
 
 (116.) The collodion-covered plate is now ready 
 for exposure in the camera* which must be pre¬ 
 viously set to receive it. Any one who is unac¬ 
 quainted with the use of the camera should ask for 
 directions from the person of whom he purchases it* 
 as no written instructions can easily explain how to 
 set the camera on the tripod* how to obtain the focus 
 for a portrait or a view* or how to expose the 
 sensitive surface.* 
 
 (117.) Collodion is now prepared of such high 
 degree of sensitiveness* that impressions can be 
 made upon it* if the light is strong and the object 
 well illuminated* in an instant; at other times* on 
 a dull* cloudy* or rainy day* it may require from 
 ten seconds to a minute and a half. By practising 
 daily upon the same object at the commencement of 
 operations* we may obtain a test by which subse¬ 
 quent efforts can be guided. Much depends upon 
 the quality of the collodion* the quality of the lens* 
 and the intensity of the actinic power. 
 
 * Glass baths are sometimes made to fit into the frame 
 of the camera in which the ground-glass screen moves. 
 The plate being immersed* is acted upon by the light while 
 in the solution. 
 
PROCESSES ON GLASS. 
 
 75 
 
 Negatives 
 
 on 
 
 Glass. 
 
 DEVELOPING. 
 
 (118.) Having allowed the collodion plate to 
 remain exposed for the time considered sufficient* 
 place the cap on the lens* shut up the slide* and 
 with all expedition carry it to the operating-room* 
 and lay the plate upon the levelling-stand* which 
 is placed in a sink or large basin* where the image 
 can now be developed. 
 
 (119.) The agent usually employed is the solu- Developing, 
 tion of pyrogallic acid* which is made as follows:— 
 
 Distilled water ... 3 ounces 
 
 Pyrogallic acid ... 9 grains 
 
 Glacial acetic acid . . 2 drachms. 
 
 Dissolve and filter. 
 
 (120.) Sufficient of this mixture to cover the 
 collodion plate must be taken in a small measure* 
 and poured gently over the surface* quickly* and 
 not all in one spot* but carried so as to be diffused 
 as soon as possible. The fluid must be kept in 
 motion by blowing it over the surface* to prevent 
 the picture being stained. The plate must be 
 watched carefully so as to stop the action as soon as 
 the image is well developed* and a gentle stream of 
 water poured over it to remove the decomposed 
 liquid as quickly as possible. In cold weather it is 
 advisable to add a few drops of nitrate of silver from 
 
Negatives 
 
 on 
 
 Collodion. 
 
 Developing 
 by Proto¬ 
 sulphate of 
 Iron. 
 
 Test of the 
 time of ex¬ 
 posure. 
 
 76 COLLODION NEGATIVES ON GLASS. 
 
 the bath to the pyrogallic acid. As this process is 
 performed the image will be seen gradually to 
 appear upon the surface of the collodion, and we 
 are then able to judge of our success. By holding 
 a piece of white paper under the image it will be 
 seen how far it is developed. When the solution 
 becomes discoloured, we may know that it has been 
 on the plate quite long enough — perhaps too long. 
 
 (121.) Another method of developing is often 
 used, viz. by protosulphate of iron. By this pro¬ 
 cess a bath is used which will serve for a number of 
 operations. It is prepared as follows :— 
 
 Distilled water .... 1 pint 
 
 Protosulphate of iron . . 1 ounce 
 
 Sulphuric acid .... 12 minims 
 Acetic acid.12 „ 
 
 Filter this solution, and pour sufficient into a bath, 
 either of glass or gutta percha, to cover the plate 
 entirely when immersed; plunge the proof in, and 
 the image will appear in three or four seconds. If 
 the impression is too faint, it can be strengthened by 
 pouring over it a solution of gallic acid, containing 
 a few drops of the nitrate of silver, which will 
 greatly improve it. 
 
 (122.) If the proof has a grey tone all over 
 it, the exposure in the camera has been too long; 
 if, on the contrary, the light parts in the object 
 remain black, it shows that the exposure has been 
 too short. 
 
PROCESSES ON GLASS. 
 
 77 
 
 Negatives 
 
 on 
 
 Collodion. 
 
 By Sulphate 
 of Iron. 
 
 FIXING THE PROOF. 
 
 ( 123 .) The fixing of the proof can be effected Eixingthe 
 by hyposulphite of soda, or by sulphate of per-oxide ^teofsoda. 
 of iron. 
 
 For the firsts make a saturated solution of hypo¬ 
 sulphite of soda, and pour it carefully over the 
 proof; it gives great transparency and vigour, but 
 impairs the solidity of the collodion. Finish by 
 washing with abundance of clean water, and set the 
 plate up to dry. Should any of the hyposulphite of 
 soda be left on the collodion, it will destroy the 
 image. 
 
 For the second, make this solution:— 
 
 Distilled water.1 pint 
 
 Sulphate of per-oxide of iron 15 grains. 
 
 Having first washed the proof, pour this solution 
 over it, and watch the developement of the image; 
 as soon as it is completed, wash the proof again 
 under a gentle stream of water, without disturbing 
 the collodion. Rinse with distilled water, and dry 
 quickly before the fire, if necessary. The salt of 
 iron will destroy the proof if allowed to remain 
 upon it too long; it leaves an opaque yellow tint 
 upon the shadows of the image which gives strength 
 to a feeble impression, and positives taken from 
 negatives thus prepared are superior to those fixed 
 by the hyposulphite of soda. 
 
78 
 
 COLLODION NEGATIVES ON GLASS. 
 
 CONVERSION OF NEGATIVES INTO 
 POSITIVES. 
 
 Collodion 
 
 on Glass. . . 
 
 (124.) A negative picture* prepared as indicated 
 above* can be converted into a positive in various 
 ways. That suggested by Sir John Herschel con¬ 
 sists in smoking the glass on the collodion side. Or 
 the proof may be backed with any black substance* 
 such as varnish* paper* velvet* &c. 
 
 Conversion (125.) Dr. Diamond obtains the picture by the 
 
 of negatives v 7 x ^ 
 
 into positives usual collodion process* and developes by proto¬ 
 nitrate of iron. The negative image being deve¬ 
 loped* a mixture of hyposulphite of soda* which 
 has undergone partial decomposition* and pyrogallic 
 acid* is poured over the plate* which is slightly 
 warmed. Upon this the darkened parts are ren¬ 
 dered brilliantly white by the formation of metallic 
 silver. The picture* being backed up with black 
 velvet* assumes the aspect of a fine daguerreotype* 
 without any of the disadvantages arising from the 
 reflexion of light from the polished silver surface. 
 
 (126.) Mr. Archer obtains this result by pouring 
 a solution of bichloride of mercury over the proof; 
 Mr. Fry* by the combined action of pyrogallic 
 acid and proto-nitrate of iron. 
 
 (127.) M. Marten’s communication to the Aca- 
 
PROCESSES ON GLASS. 
 
 79 
 
 demy of Sciences at Paris details the following 
 method of operations for producing positives directly 
 on the glass plate : Make a solution of gun-cotton in 
 ether. The gun-cotton is prepared by heating 2 
 parts of cotton wool with 50 parts of nitrate of 
 potash and 100 parts of sulphuric acid. This, 
 when well washed and dried, is soluble in a mix¬ 
 ture of 10 volumes of ether and 1 volume of alcohol, 
 to which are added 15 grains of nitrate of silver, 
 converted into the iodide by iodide of ammonium, 
 and dissolved in 300 grains of alcohol. 
 
 (128.) The plate of glass covered in the usual 
 way with this substance is plunged before it be¬ 
 comes dry into a bath composed of 
 
 Nitrate of silver ... 8 parts 
 
 Nitric acid. 5 „ 
 
 Distilled water .... 100 „ 
 
 (129.) For developing it is plunged into a bath 
 of sulphate of protoxide of iron, and carefully 
 washed. The picture is now a negative , but on 
 plunging it into a bath of the double cyanide of 
 silver and potassium, it immediately becomes posi¬ 
 tive. It must next be washed and dried. 
 
 The cyanuret bath is composed of 
 
 Water. 2 quarts 
 
 Cyanuret of potassium 375 grains 
 
 Nitrate of silver . . 60 „ 
 
 The pictures produced in this manner possess 
 great brilliancy. 
 
 Collodion 
 on Glass. 
 
POSITIVE PICTURES ON COLLODION. 
 
< 
 
 
 
POSITIVES ON COLLODION. 
 
 (130.) These resemble in many respects da¬ 
 guerreotypes^ but are free from the objectional glare 
 peculiar to the polished silver plates. 
 
 For direct positives the method of coating and 
 exciting the sensitive surface is the same as that 
 used for negatives. After exposure in the camera* 
 which need not be half so much as for negatives* 
 the developing process is conducted with either py- 
 rogallic acid or protosulphate of iron* with the 
 addition to either of one or two drops of nitric 
 acid. Various formulae have been suggested; the 
 following will be found as useful as any:— 
 
 Pyrogallic acid .... 8 grains 
 Distilled water .... 8 ounces 
 
 Acetic acid.1 drachm. 
 
 When mixed* add one or two drops of nitric acid* 
 according to its strength. Mix and filter. Or* 
 
 Distilled water .... 1 ounce 
 
 Protosulphate of iron . . 20 grains 
 
 Acetic acid.1 drachm 
 
 Nitric acid.1 or 2 drops. 
 
 Either of these developing solutions must be ap¬ 
 plied by gently pouring the fluid along the margin 
 
84 
 
 POSITIVE PICTURES ON COLLODION. 
 
 of the glass plate, and when sufficient has accumu¬ 
 lated, by a slight movement of the hand the fluid is 
 made to cover the whole surface of the collodion 
 quickly and at once, because if the solution is poured 
 on to the collodion, the action of the nitric acid is so 
 energetic, that it would be more intense at that par¬ 
 ticular spot where the stream falls, and an unequal 
 effect be produced. 
 
 As soon as the picture is visible, or, as soon as 
 it begins to appear, the developing solution must be 
 poured off, and the proof well washed with water, 
 and then fixed in the usual manner by hyposulphite 
 of soda. In drying it loses its transparency, but 
 this can be restored by varnishing. 
 
 When the picture developes very slowly, it is 
 due to insufficient exposure in the camera; in conse¬ 
 quence of which the shadows, instead of being strong 
 and even, are covered with a multitude of spots of 
 metallic silver, which extend gradually over the 
 whole plate. This effect is due to the de-oxydising 
 power of the nitric acid. 
 
 When the plate has been exposed too long in the 
 camera the developing solution acts with so much 
 rapidity on those parts which have received most 
 light, that it must be poured off before the half- 
 lights are visible; in consequence of which the sha¬ 
 dows will be very strong and pure, but the lighter 
 parts will be vague and indistinct. 
 
ALBUMIN ON GLASS. 
 
ALBUMIN ON GLASS. 
 
 (131.) This process is based on tbe property 
 possessed by albumin, of becoming insoluble upon 
 the application of heat. The application of this 
 substance to photography on glass is due to M. 
 Niepce de St. Victor. 
 
 (132.) Take the whites of eggs, and to every 
 100 grains add 1 grain of iodide of potassium, or 
 of iodide of ammonium. Beat the whole into a 
 froth; leave it all night to settle; decant the clear 
 liquor, and, if necessary, strain through fine muslin. 
 
 (133.) Take a thin piece of plate glass — if 
 ground on the surface it is preferable, because 
 the albumin will adhere better, clean it well with 
 distilled water, rub it dry with a piece of tissue 
 paper, and finish with a piece of cotton wool. 
 
 (134.) Place it on a stand perfectly level; then 
 pour over it freely the albumin, until the plate is 
 quite covered. Take it in the hands, and so incline 
 it that an even layer of the greatest thinness pos¬ 
 sible shall be spread over its surface, and replacing 
 
 Negatives. 
 Albumin on 
 glass. 
 
88 
 
 ALBUMIN ON GLASS. 
 
 it upon the horizontal stand, put it away in a box 
 or closet out of the reach of dust. 
 
 (135.) Before putting the albuminised glass into 
 the bath of aceto-nitrate of silver, it must be held 
 before the fire until every trace of moisture is 
 removed. The application of the bath is a very 
 delicate operation, for the least hesitation in plung¬ 
 ing the glass plate into the fluid will cause irregu¬ 
 larities on the surface, which nothing can remove. 
 Fill the bath about two-thirds with the following 
 solution:— 
 
 Distilled water ... 5 drachms 
 
 Nitrate of silver ... 24 grains 
 Acetic acid .... 30 „ 
 
 (136.) Let the albuminised plate remain in two 
 or three minutes; then remove it, wash in distilled 
 water, and dry in the dark. 
 
 (137.) The albumin plates thus prepared can 
 be preserved one or two days before exposing them 
 in the camera. 
 
 (138.) The image can be developed in the same 
 manner as the negatives on paper, putting into the 
 bath warm gallic acid containing not more than 
 one-sixteenth of its volume of aceto-nitrate of 
 silver. 
 
 (139.) We obtain much more rapidity by deve¬ 
 loping the image with a bath of saturated solution 
 of protosulphate of iron, containing one-sixteenth of 
 glacial acetic acid. 
 
ALBUMIN ON GLASS. 
 
 89 
 
 Negatives. 
 
 (140.) The time in the camera may thus he 
 diminished three-fonrths. When it is well deve¬ 
 loped it can he fixed by the same process indicated 
 for paper (102). 
 
 (141.) Mr. Talbot’s Instantaneous Process.— 
 
 1. Coat a plate of glass with a mixture of albumin 
 and water in equal proportions. 
 
 2. Dip the plate in a solution of three grains of 
 nitrate of silver to an ounce of a strong mixture of 
 alcohol and water, and wash it with distilled water. 
 
 3. To a saturated solution of prot-iodide of iron 
 add, first, an equal volume of acetic acid, and then 
 ten volumes of alcohol. Keep the mixture for two 
 or three days, and dip the plate into it. 
 
 4. Make a solution of seventy grains of nitrate 
 of silver to one ounce of water. To three parts of 
 this add two of acetic acid. This is the sensitive 
 mixture, and the plate must be rapidly immersed 
 in it. 
 
 5. Develope with one part of a saturated solution 
 of protosulphate of iron to three parts of water, and 
 fix with hyposulphite of soda. 
 
 By these means Mr. Talbot obtained, at the 
 Royal Institution, the image of a printed paper 
 made to revolve upon a wheel, and lighted up 
 during the fraction of a second by a powerful 
 electrical discharge. 
 
DESCRIPTION OE THE CHEMICALS 
 USED IN PHOTOGRAPHY. 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 (142.) Acetic Acid. Glacial or Crystallisable. 
 (C 4 H 3 0 3 H0.) 
 
 (Equivalent, 60 = C24 + H4 + 0 32.) 
 
 This acid is prepared by distillation from the 
 impure pyroligneous acid of commerce. It is em¬ 
 ployed in photography, added to a solution of nitrate 
 of silver, for the purpose of facilitating the decompo¬ 
 sition of the iodide of potassium, as well as to assist 
 the penetration of the solutions into the paper. 
 
 A sheet of iodized paper placed upon the solu¬ 
 tion of aceto-nitrate of silver gives rise to the fol¬ 
 lowing decomposition: the iodide of potassium is 
 decomposed by the nitrate of silver under the ener¬ 
 getic action of the acetic acid: the silver combines 
 with the iodine on the paper, and forms an insoluble 
 iodide of silver, which includes a little acetate of 
 silver, and the potash of the iodide forms the nitrate 
 of potash in solution. 
 
 Acetic acid is useful to remove the spots on the 
 negative proofs formed by the oxide of silver. 
 
94 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 (143.) Albumin. 
 
 This substance is readily obtained, the whites of 
 eggs consisting wholly of that principle. When 
 thinly spread upon a glass plate* and exposed to 
 evaporation* it dries up to a yellow gum-like sub¬ 
 stance* in which state it may be preserved for any 
 length of time. In the fluid state* mixed with the 
 sensitive iodide of silver* it is employed to make 
 photographic pictures on—either negatives or posi¬ 
 tives : to the latter it imparts great brilliancy. 
 
 (144.) Alcohol. 
 
 This well-known liquid is of various application 
 to photography; it is added to the etherial solution 
 of gun-cotton (collodion)* and to various sensitive 
 preparations* for which purposes it must be free 
 from impurity; it is sometimes contaminated with 
 potassa and other foreign bodies : a ready test of its 
 purity is to pour a few drops upon a piece of clean 
 plate glass* and evaporate it over a lamp; if pure* it 
 leaves no stain. 
 
CHEMICALS USED IN PHOTOGKAPHY. 
 
 95 
 
 (145.) Ammonia Solution. (N H 3 .) 
 
 (Equivalent, 17 = N 14 + H 3.) 
 
 Water dissolves about 700 times its volume of 
 ammonia (ammoniacal gas)* forming the well- 
 known spirits of hartshorn* or volatile alkali. It is 
 a very powerful reagent* and must be employed in 
 photography with great caution* as it forms highly- 
 explosive compounds with silver* iodine* and chlorine. 
 Ammonia completely dissolves chloride of silver: 
 when it is added to a solution of nitrate of silver a 
 black precipitate falls* which is an oxide of silver; 
 by carefully adding more ammonia* drop by drop* 
 this powder is redissolved. The clear solution 
 (ammonio-nitrate of silver) was first suggested by 
 Dr. Alfred S. Taylor* as a wash for positive paper. 
 His solution is made by dissolving 35 grains of 
 nitrate of silver in 1 ounce of distilled water* and 
 gradually adding strong solution of ammonia until 
 the precipitate is just redissolved. The paper* pre¬ 
 viously prepared with the muriate of ammonia 
 wash* is to be carefully wetted with this solution* 
 and dried. If any of the ammonio-nitrate dries 
 round the stopper of the bottle in which it is kept* 
 the least friction will cause it to explode violently; 
 it is better* therefore* to keep none prepared* but to 
 make as much as is required for use at one time. 
 
96 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 Iodised collodion, when kept too long, decom¬ 
 poses, and is no longer sensitive to light; its sensi¬ 
 tiveness may, however, be restored by the addition 
 of a few drops of solution of ammonia, which neu¬ 
 tralises the acid formed, and sets the iodine free. 
 
 A weak solution of ammonia is the best “ fixing” 
 agent for those proofs which have been taken with 
 nitrate of silver, or the ammonio-nitrate. 
 
 (146.) Bromide of Ammonium. (NH 3 Br.) 
 
 (Equivalent, 97 = Br 80 + N 14 + H 3.) 
 
 A solution of this salt in its weight of water 
 forms an excellent material for u fixing” the positive 
 proofs. It is only necessary to leave them for a 
 quarter or half-hour in a bath of this solution, and 
 afterwards wash them in several waters, when they 
 will be completely fixed. This quality is due to the 
 facility with which ammonia dissolves chloride of 
 silver. 
 
 This salt can also be used in the preparation of 
 sensitive paper, both for negatives and positives. 
 M. Le Gray’s formula is— 
 
 Distilled water . . . 1000 parts. 
 
 Iodide of potassium . . 15 „ 
 
 Bromide of ammonium 4 „ 
 
 Sugar of milk .... 40 „ 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 97 
 
 (^147.) Bromide of Potassium. (Br K.) 
 (Equivalent, 119 = Br 80 + K 39.) 
 
 Bromide of potassium serves to form the bro¬ 
 mide of silver* by decomposing the nitrate; this salt 
 is less sensitive to light than the iodide. It is inso¬ 
 luble in water and alcohol* but dissolves in solution 
 of ammonia and hyposulphite of soda. It is used by 
 M. Le Gray and others in combination with chloride 
 of sodium in the preparation of sensitive paper. 
 The formula given is — 
 
 Distilled water. . . . 10 drachms 
 
 Bromide of potassium . 1 „ 
 
 Chloride of sodium . . 1 *, 
 
 Paper washed with this preparation is placed 
 upon the aceto-nitrate of silver* as indicated in other 
 preparations* and afterwards proceeded with in the 
 same manner. There appear to be some difficulties 
 attending its employment. We must content our 
 selves* therefore* with merely indicating its use. 
 
 (148.) Bromide of Silver. (Ag Br.) 
 
 (Equivalent, 188=Ag 108-j-b R 80.) 
 
 Bromide of silver is obtained by decomposing 
 nitrate of silver by bromide of potassium. It is one 
 
 H 
 
98 
 
 CHEMICAXS USED IN PHOTOGRAPHY. 
 
 of the most sensitive preparations used in photo¬ 
 graphy yet discovered. It requires to be employed 
 in a very diluted state to effect the greatest change, 
 and should be applied to the paper by the following 
 means. 
 
 Wash the paper with the following solution :•— 
 
 Bromide of potassium ... 40 grains 
 Chloride of sodium .... 40 „ 
 
 Distilled water.1 ounce 
 
 The addition of the chloride of sodium gives great 
 sensitiveness. When dry, float the paper upon a 
 solution of nitrate of silver, forty grains to the ounce 
 of water; dry the paper quickly, without scorching, 
 and then apply another wash of the solution of 
 nitrate of silver. The addition of a drachm of 
 alcohol to the nitrate of silver gives a deeper black 
 tint to the proofs. 
 
 (149.) Caustic Potassa. (K O, H O.) 
 
 (Equivalent, 56 = K 39 + H 1 + 0 16.) 
 
 This alkali, when added to a solution of nitrate 
 of silver, precipitates the metal in the state of a 
 protoxide. A small quantity dissolved in water is 
 used to give a variety to the tones of the proofs 
 after they have been submitted to the action of the 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 99 
 
 hyposulphite of soda. It acts with great energy, 
 and the proof must, therefore, be carefully watched, 
 and plunged into clean water as soon as the desired 
 effect is produced. 
 
 (150.) Chloride of Barium. (Ba Cl 2 H O. 
 
 Muriate of Barytes.) 
 
 (Equivalent, 122 = Cl 36 + Ba 68 + H 2 + 0 16.) 
 
 Paper for positives prepared with this salt in the 
 same manner as when chloride of sodium or hydro¬ 
 chlorate of ammonia are employed to decompose 
 the nitrate of silver, yield very good brown tones. 
 When the proof has been exposed to the light a 
 sufficient length of time, it is washed in water con¬ 
 taining ten per cent of protosulphate of iron, which 
 yields upon the paper a white insoluble precipitate 
 of pleasing effect. After it has remained about five 
 minutes in the bath, it is washed, and the u fixing ” 
 continued with hyposulphite of soda, as with the 
 other preparations. Chloride of barium is soluble 
 in cold water, 100 grains dissolving about 43 grains 
 of the salt at a temperature of 60°, and 78 grains 
 at 223°, which is the boiling point of the saturated 
 solution. 
 
 The soluble salts of barium are poisonous. 
 
100 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 (151.) Sesqui-Chloride of Gold. (Au 2 Cl 3 .) 
 
 (Equivalent, 502 = Au 2 394 + Cl 3 108.) 
 
 Chloride of Gold is prepared by dissolving one 
 part of gold* in a state of fine powder* in three parts 
 of nitro-hydrochloric acid (aqua regia). In com¬ 
 bination with hyposulphite of soda* it yields the 
 sel d’or* in a bath of which the positive proofs may 
 be placed after they are fixed by the hyposulphite 
 of soda; it gives to the picture a very rich* deep 
 violet tone (106). 
 
 It is also useful to develope faint negatives* im¬ 
 parting to them immediately a remarkable black 
 tint in the shadows* and at the same time gives 
 great whiteness to the lights. It must be applied 
 after the negatives have been fixed by the hypo¬ 
 sulphite of soda. 
 
 (152.) Chloride of Silver. (Ag Cl.) 
 
 (Equivalent, 144—Ag 108-f-C l 36.) 
 
 This salt is rapidly acted upon by light* hence it 
 has been extensively used in photography: it is 
 readily obtained whenever we mix a soluble chlo¬ 
 ride with a soluble salt of silver; as* for instance* 
 
CHEMICALS USED IN PH0T0GKAPHY. 
 
 101 
 
 chloride of sodium with nitrate of silver. When 
 paper is washed with a solution of the chloride of 
 sodium, and afterwards with the nitrate of silver, 
 the latter salt is decomposed and converted into the 
 chloride of silver. 
 
 A coating of chloride of silver can also he 
 obtained by the combination of hydrochloric acid, 
 hydrochlorate of ammonia, or chloride of strontium, 
 and of most other chlorides with the nitrate of 
 silver. The results are nearly the same, and the 
 coating of chloride of silver is equally sensitive. 
 Upon the whole the hydrochlorate of ammonia 
 will be found preferable, because it attracts but 
 little moisture from the air, and paper prepared 
 with it will keep good a long time. 
 
 Chloride of silver is insoluble in water and in 
 nitric acid. Diluted hydrochloric acid, and the 
 alkaline cyanides and chlorides, dissolve it readily. 
 Solutions of ammonia and of hyposulphite of soda are 
 the most useful solvents, and they serve to “ fix ” the 
 positive images. 
 
 Chloride of silver darkens rapidly under the 
 influence of light, and is even more sensitive than 
 the iodide of silver; but it cannot be used for nega¬ 
 tives, for the effect of the gallic acid is to blacken it 
 all over. Were it not for this defect, it vmuld 
 supply an excellent negative paper for the camera. 
 
 But, on the other hand, chloride of silver is of 
 the greatest value for obtaining positive proofs with- 
 
102 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 out the aid of a reagent to develope the image. 
 Those portions acted upon by light are rapidly 
 brought to a state of sub-oxide, and to the metallic 
 state, if the exposure is prolonged. These oxides 
 and metallic silver being black, we have at once all 
 the qualities desired in this sort of paper; therefore 
 it would be useless to employ gallic acid to produce 
 the black. 
 
 To arrest the action of light, it is sufficient to 
 remove the soluble salts from the surface of the 
 paper. 
 
 (153.) Chloride of Sodium. (Na Cl, Muriate 
 of Soda.) 
 
 (Equivalent = 60 Cl 37 + Na 23.) 
 
 Chloride of sodium is familiarly known as com¬ 
 mon culinary salt. It is obtained in greater purity 
 by saturating carbonate of soda with hydrochloric 
 acid. In photography it is used to prepare the 
 positive paper, upon which a coating of chloride of 
 silver is produced by decomposing the aceto-nitrate 
 of silver with a chloride. 
 
 Mixed with a small quantity of iodide and of 
 bromide of potassium, the chloride of sodium sup¬ 
 plies us with an excellent preliminary wash for the 
 negative paper. 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 103 
 
 (154.) Chloride of Strontium. (Sr Cl, 6 H O.) 
 
 (Equivalent, 134 = Sr 44 + Cl 36 + H 6 + 0 48.) 
 
 The use of this salt can only be allowed when 
 no other chloride is at hand to decompose the 
 nitrate of silver, as it attracts much moisture from 
 the air. 100 grains of cold water dissolve 50 
 grains, and boiling water much more, of this salt. 
 
 (155.) Collodion. 
 
 Collodion is gun-cotton dissolved in ether; its 
 solubility depends upon the mode of preparing the 
 gun-cotton. Many formulae have been given for 
 the purpose; that which is most readily soluble is 
 obtained by soaking clean cotton wool in a saturated 
 solution of nitrate of potash. After thoroughly 
 soaking for some time, pressing it occasionally with 
 a glass rod, remove the excess of nitrate of potash, 
 and pour over the cotton a sufficient quantity of sul¬ 
 phuric acid, with which a small quantity of nitric 
 acid has been mixed; this must be done in the open 
 air, or under a chimney, to carry off the noxious 
 fumes. In about a minute or two remove the cot¬ 
 ton and place it on a funnel, and pour over it a 
 
104 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 stream of clean water* until the washings cease to 
 turn litmus paper red. It is then squeezed by the 
 hand to express the water* left to drain* and dried 
 spontaneously in the air of an apartment. As it is 
 now the well-known highly-explosive compound* 
 gun-cotton* we need scarcely remark that great 
 caution must be exercised in the use of it. 
 
 When dry it is dissolved in sulphuric ether* as 
 follows:— 
 
 Sulphuric ether ... 18 fluid ounces 
 
 Alcohol .... 
 Gun-cotton . . . 
 
 Solution of ammonia 
 
 6 drachms 
 30 grains 
 5 drops. 
 
 Make this solution in a flask* and by agitating the 
 mixture the gun-cotton quickly dissolves. Then 
 add five grains of iodide of ammonium: when dis¬ 
 solved* filter the whole through fine muslin* in a 
 glass filter* covered to prevent evaporation. After 
 standing a day or so* it is fit for use. 
 
 As some portion of the ether evaporates every 
 time the stopper is removed from the bottle in which 
 this solution is kept* it is preferable to have a small 
 bottle containing only as much as is required to take 
 three or four pictures on* and replenish it from the 
 larger stock-bottle as required. If it becomes too 
 thick it can be diluted with more ether. 
 
 There are other methods of iodizing the collo¬ 
 dion ; the following is Mr. Archer’s method:— 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 105 
 
 Make a saturated solution of iodide of potassium in 
 alcohol^ say one ounce; and add to it as much iodide 
 of silver as it will dissolve. Or, to one ounce of 
 alcohol add an excess both of iodide of potassium 
 and iodide of silver. After a day or two, and with 
 repeated shaking at intervals to facilitate the opera¬ 
 tion, a saturated solution of the two salts will be 
 obtained; and if this is filtered off into another bottle 
 it will be always ready for use. The first bottle can 
 be kept as a stock-bottle, to obtain a still further 
 supply by replenishing it with alcohol, and adding 
 now and then small additional quantities of the two 
 salts. The iodide of silver can be readily obtained 
 by precipitation. 
 
 (156.) Cyanide of Potassium. (KCy.) 
 
 (Equivalent, 65 — C 12 + N 14 -f K 39.) 
 
 This salt is a compound of prussic acid with 
 potassium, and a very deadly poison. It is used in 
 photography; added to nitrate of silver, it yields 
 cyanide of silver, which is very sensitive to the 
 action of light; but when added to the iodide and 
 the fluoride of potassium, it forms a triple salt of 
 great sensitiveness. Cyanide of silver is insoluble 
 in water, and in diluted nitric acid. It is decom- 
 
106 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 posed by hydrochloric acid, and changed into chlo¬ 
 ride of silver. Solution of ammonia, the alkaline 
 cyanides, and especially hyposulphite of soda, dis¬ 
 solve it. 
 
 The cyanide of potassium dissolves the iodide, 
 chloride, and bromide of silver; it also dissolves the 
 protoxides and suboxides of this metal when they 
 are precipitated by gallic acid. A solution of the 
 salt is useful, with the aid of a brush, to remove the 
 black spots which injure the proofs; only it must be 
 applied with great caution, and the proof immersed 
 in water immediately after its application, else it 
 may destroy it entirely. 
 
 The cyanide of potassium is useful for removing 
 the stains of nitrate of silver from the hands. Great 
 caution must be observed in using it that the skin is 
 not wounded, else the poison would be quickly ab¬ 
 sorbed, and fatal consequences ensue. 
 
 (157.) Ether. 
 
 A colourless, volatile fragrant liquid, very com¬ 
 bustible, slightly soluble in water, and mixable with 
 alcohol in all proportions. In photography its chief 
 use is as a solvent for gun-cotton to produce Collo¬ 
 dion, q. v . 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 107 
 
 (158.) Fluoride of Ammonium. (Az H 3* Fl.) 
 
 (Equivalent, 36 = Fl 19 + Az 14 + H 3.) 
 
 This salt, added to the iodide of potassium, im¬ 
 parts a great increase of sensitiveness; but it does 
 not appear to be so useful as the fluoride of potas¬ 
 sium. 
 
 (159.) Fluoride of Potassium. (K Fl.) 
 
 (Equivalent, 58 = El 19 -f K 39.) 
 
 Fluoride of potassium adds to the sensitiveness 
 of the prepared paper when mixed with the iodide 
 of potassium. The process in which the fluorides 
 are employed is termed the Fluorotype. 
 
 (160.) Gallic Acid. (C 7 H 3 0 5 , 2 H O.) 
 
 (Equivalent, 103 = C42-j-H5 + 0 56.) 
 
 This acid is obtained from nut-galls. It is em¬ 
 ployed in photography as a developing agent for 
 negative proofs. It gives to them the black tints. 
 
108 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 by its combination with the salts of silver* which 
 have lost their oxygen by the action of light. 
 
 All the salts of silver* generally* which are in a 
 state of snb-oxide* or near the metallic state* are 
 precipitated of a black-brown colour by this acid: 
 consequently we can employ it for developing the 
 proofs made by the iodide* bromide* fluoride* or 
 cyanide* as well as those made by the iodide of 
 silver. 
 
 Some practitioners recommend that this salt be 
 used in a concentrated state* as a rapid developing 
 agent. M. Le Gray uses a weak solution* fifteen to 
 thirty grains to a quart of distilled water* by which 
 means there is much less danger of spotting the 
 proofs: it takes more time to develope them* which 
 is compensated for by their greater beauty. 
 
 Gallic acid is but slightly soluble in cold water* 
 1 grain of the acid requiring 100 grains of water for 
 its solution; but 3 grains of boiling water will dis¬ 
 solve 1 grain of the acid. The solution is gradually 
 decomposed by keeping. 
 
 When the proof is almost entirely developed* if 
 we add a little of the aceto-nitrate of silver the sha¬ 
 dows become immediately more intense; but it must 
 be carefully watched* else too great an intensity will 
 take place* from a rapid precipitation of gallate of 
 silver. 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 109 
 
 (161.) Hydeociiloeate of Ammonia. (Az H 3, H Cl, 
 Mukiate of Ammonia, Sal Ammoniac.) 
 
 (Equivalent, 54 = Az 14 -f H 4 -f- Cl 36.) 
 
 Hydrochlorate of ammonia is very useful in the 
 preparation of positive paper; it decomposes nitrate 
 of silver, forming the chloride of that metal, and is 
 a better preparation than chloride of sodium, since 
 it attracts less moisture from the air. 100 parts of 
 cold water dissolve 36 parts of the salt, and boiling 
 water its own weight; and it is also very soluble in 
 alcohol. 
 
 (162.) Hydeochloeic Acid. (Cl H, Mueiatic 
 Acid.) 
 
 (Equivalent, 37 = Cl 36 + H 1.) 
 
 This acid is prepared by decomposing common 
 salt with sulphuric acid. Diluted with water it has 
 been employed to give a rich brown tone to the 
 proofs after they have passed through the bath of 
 hyposulphite of soda, and been washed in water. 
 Mixed with nitric acid it forms the aqua regia in 
 which gold is soluble, and from which the chloride 
 of gold, or sel d’or, is obtained. 
 
110 
 
 CHEMICALS USED IN PHOTOGBAPHY. 
 
 (163.) Hypochlokite op Potassa. (K O, Cl O.) 
 
 (Equivalent, 91 = K 39 + 0 16 + Cl 36.) 
 
 This salt has bleaching properties* although in¬ 
 ferior to chloride of lime. Dissolved in its weight 
 of water* the solution is applied to spots or stains on 
 the prepared paper. It also fixes the positive proofs* 
 and yields very agreeable tones. The hypochlo¬ 
 rite of lime (bleaching powder) produces the same 
 effect. 
 
 (164.) Hyposulphite of Soda. (Na O* 
 S 2 0 2 + 5 H O.) 
 
 (Equivalent, 124. Na 23 + S 32 + 0 64 + H 5.) 
 
 This salt is very soluble in water at all tem¬ 
 peratures. It is of great service in photography* 
 for “ fixing ” the proofs* which it accomplishes by 
 dissolving the salts of silver* such as the chloride* 
 iodide* &c.* which are insoluble in w^ater* and so 
 removing them from the proof* and thereby pre¬ 
 venting any further chemical change in the im¬ 
 pression. The solution of hyposulphite of soda* 
 after it retains some of the salts of silver in solution* 
 is more useful for the fixing process* as it gives 
 better black tones than when first employed. It is 
 the best fixing material yet discovered* both for 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 Ill 
 
 positives and negatives; and by careful manipu¬ 
 lation almost every variety of tone can be given to 
 the proofs. With faint positive proofs it is best to 
 soak them for a few hours in a bath of clean water, 
 before submitting them to the action of the hypo¬ 
 sulphite of soda; by which means the soluble salts of 
 silver are removed without affecting those parts 
 acted upon by the light, which constitute the blacks. 
 Thus we abridge the time necessary for the action 
 of the hyposulphite, and the fixed image is found to 
 be more vigorous than if it had been placed at once 
 in the hyposulphite of soda. 
 
 (165.) Iodide of Ammonium. (Az. H 3, H Io.) 
 (Hydriodate of Ammonia.) 
 
 (Equivalent, 145 = H Io 128 + N 14 + H 3.) 
 
 The hydriodate of ammonia is a compound very 
 easily decomposed: it must be kept suspended in a 
 bottle containing a small quantity of carbonate of 
 ammonia. 
 
 Sensitive papers may be prepared by washing 
 them with a solution of this substance previous to 
 placing them upon the aceto-nitrate of silver; an 
 impression is received with great rapidity, which is 
 developed with facility by gallic acid, to which a 
 little acetate of ammonia has been added. 
 
112 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 Paper prepared with the hydriodate of ammonia 
 will not keep long; it loses its sensitiveness by the 
 continuous evaporation of the ammonia. 
 
 (166.) Iodide of Potassium. (K Io.) (Hydrio¬ 
 date of Potash.) 
 
 (Equivalent, 166 = K 39 + Io 127.) 
 
 Iodide of potassium is one of the principal che¬ 
 mical agents in photography. It serves to form the 
 iodide of silver, which is the sensitive salt upon 
 which light acts with the greatest energy. This 
 iodide of silver is insoluble in water, but soluble in 
 hyposulphite of soda, which is used for “ fixing” the 
 negative proofs. 
 
 (167.) Iodide of Silver. (Ag I.) 
 
 (Equivalent, 235 =Ag 108 + 1 127.) 
 
 Iodide of silver is obtained by adding iodide of 
 potassium to a solution of nitrate of silver; decom¬ 
 position ensues, the nitric acid leaves the silver and 
 unites with the potash, while the liberated iodine 
 combines wdth the silver, and falls as a yellow pre¬ 
 cipitate, which must be well washed in distilled 
 water, being insoluble therein, to remove the nitrate 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 113 
 
 of potash^ and then dissolved in a saturated solution 
 of iodide of potassium. This mixture is to be added 
 to the collodion in small quantities at a time; and 
 agitated until dissolved. 
 
 Formula for the preparation of iodide of silver: 
 
 Distilled water.1 ounce 
 
 Nitrate of silver.30 grains. 
 
 Add to it as much of an aqueous solution of iodide 
 of potassium as will precipitate the whole of the 
 nitrate of silver as an iodide. When this precipi¬ 
 tated iodide of silver has settled; the fluid must he 
 decanted; and fresh water added several times, to 
 wash out all the nitrate of potash. Drain off all the 
 water, and when dry cover the iodide with sufficient 
 alcohol to keep it moist. This iodide of silver is 
 soluble in iodide of potassium: the quantity re¬ 
 quired to iodize the collodion cannot be stated with 
 certainty; about ten or twelve drops to the ounce is 
 usually added. 
 
 ( 168 . ) Nitrate of Baryta. (Ba O, N O 5 .) 
 
 (Equivalent, 130*5 = Ba 68*5 -{- N 14-j- 0 48.) 
 
 This salt is prepared by dissolving the native 
 carbonate of baryta in muriatic acid. It is used in 
 photography to obtain the proto-nitrate of iron, by 
 decomposing with it a solution of proto-sulphate of 
 iron. 
 
 i 
 
114 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 (169.J Nitrate of Protoxide of Iron. 
 
 (Fe 0,N0 5 ) 
 
 (Equivalent, 90 = Fe 28 + N 14 + 0 48.) 
 
 A solution of this salt is employed for develop¬ 
 ing collodion proofs as negatives, either alone or in 
 combination with pyrogallic acid. It is best pre¬ 
 pared by decomposing a solution of nitrate of baryta 
 by a solution of the sulphate of protoxide of iron in 
 the following manner:—Make a solution in three 
 ounces of hot water of 300 grains of nitrate of 
 baryta; when dissolved, add 320 grains of sulphate 
 of protoxide of iron, in crystals, and stir the mixture 
 with a glass rod until all are dissolved. After a 
 while the sulphate of barytes formed by the decom¬ 
 position falls to the bottom of the vessel, and the 
 supernatant liquid, the proto-nitrate of iron, may be 
 decanted, and kept in a well-stoppered bottle for 
 use. This solution is very liable to decomposition; 
 but so long as it retains an emerald green colour it is 
 fit for use, but if it turns red it should be thrown 
 away. 
 
 (170.) Nitrate of Silver. (Ag O, N 0 5 .) 
 
 (Equivalent, 170 = Ag 108 +N14 + 0 48.) 
 
 Nitrate of silver is a very important ingredient 
 in photography; it is a compound of nitric acid with 
 the metal silver in its highest state of oxydation. It 
 is decomposed by iodide of potassium, by which 
 
CHEMICALS USED IN PH0T0GKAPHY. 
 
 115 
 
 iodide of silver is obtained. The best nitrate of 
 silver is in thin colourless crystalline plates (the 
 fused is generally adulterated), which are soluble in 
 an equal weight of cold water. Exposed to light 
 this salt blackens, especially if any organic matter 
 is present; advantage is taken of this property to 
 prepare the sensitive solutions which are spread 
 upon the paper, and other media employed in ob¬ 
 taining photographic pictures. It is readily decom¬ 
 posed by chlorides, bromides, fluorides, cyanides, 
 &c., producing salts of exquisite sensibility; and 
 if these, or some of them, are added to the 
 iodide of potassium, in the first preparation of the 
 paper, when they are submitted to the contact of 
 the nitrate of silver, compounds are formed, appa¬ 
 rently intermediate in their atomic constitution 
 between the protoxide and the suboxide of silver. 
 As soon as the light strikes these preparations in 
 this condition, they pass from the state intermediate 
 between the protoxide and suboxide to the metallic 
 state, the silver is reduced , and is precipitated in a 
 dark-coloured form by gallic, or pyrogallic acid, in 
 various degrees of strength, according to the extent 
 of the reduction. The chief object and aim in the 
 future of photography is in the direction of the 
 developing agents. We have found substances 
 which require but an instantaneous exposure to the 
 action of light to effect that change, which once set 
 up is continued and completed by suitable deve¬ 
 loping agencies. 
 
116 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 (171.) Nitrate of Zinc. (Zn O. Az O 5 .) 
 
 (Equivalent/94 = Zn32 + Az14 + 0 48.) 
 
 Nitrate of zinc is obtained by dissolving granu¬ 
 lated zinc in diluted nitric acid. It lias been added 
 by some photographers to the aceto-nitrate of silver, 
 under the impression that it augments the sensi¬ 
 bility of the preparation, and preserves the whites 
 in the proofs by precipitating upon the surface of 
 the paper a coating of the white oxide of zinc, M. 
 Le Gray uses it to give body to thin paper, by 
 washing it with a solution of 6 parts of nitrate of 
 zinc in 100 parts of water, drying it, and then im¬ 
 mersing it in the bath of iodide of potassium. The 
 precipitate, falling upon the surface of the paper, 
 closes the pores, and it is insoluble in water. 
 
 (172.) Nitric Acid. (N, 0 5 ) 
 
 (Equivalent, 54 = Nitrogen, 14 + Oxygen, 40.) 
 
 This acid is obtained by distilling a mixture 
 of equal parts, by weight, of nitrate of potash and 
 sulphuric acid. It is very abundant in commerce, 
 and is useful in photography to form the nitrate of 
 silver; and in combination with muriatic acid (aqua 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 117 
 
 regia) to yield the chloride of gold added to 
 the sulphate of the protoxide of iron, it converts 
 it into the sulphate of the peroxide. 
 
 It is also employed to darken the tone of the 
 shadows of the positive proofs after they have been 
 submitted to the action of the hyposulphite of soda. 
 Its action is similar to that of the muriatic acid used 
 for the same purpose. 
 
 As it possesses great solvent powers, it is very 
 useful for removing the deposit left on the gutta 
 percha or porcelain dishes, &c.; but the greatest 
 care must be taken that no free acid appears in any 
 of the preparations used in photography; for how¬ 
 ever useful in its combinations with silver, &c. 
 alone, it has a most destructive influence by its 
 deoxydising qualities, neutralising the effects pro¬ 
 duced by the agency of light. 
 
 (173.) Proto-Chloride of Mercury. (Hg Cl.) 
 
 (Equivalent, 136=Hg 100 + Cl 36.) 
 
 The proto-chloride of mercury, commonly called 
 the fo'-chloride, or corrosive sublimate, is employed 
 
118 
 
 CHEMICALS USED m PHOTOGRAPHY, 
 
 in photography for converting collodion negatives 
 into positives. 
 
 Saturate muriatic acid with proto-chloride of 
 mercury ; add one part of the solution to six parts 
 of water; after the proof is fixed and washed, pour a 
 small quantity over it from one corner, and allow it 
 to run evenly over the proof. A peculiar whitening 
 appears, and a singularly delicate picture is pro¬ 
 duced. After being washed and dried, it can he 
 varnished and kept as a positive; but, what is most 
 singular, even after this bleaching, it can be recon¬ 
 verted into a negative of much greater strength 
 than it was originally, by washing it with a weak 
 solution of hyposulphite of soda, or of ammonia : the 
 white picture vanishes, and a black negative re¬ 
 appears. 
 
 When the proto-chloride of mercury is first 
 applied to the negative it deepens its shades, and 
 greatly strengthens the face of the proof, and the 
 process of change can be stopped at this point by 
 simply immersing the plate in water. The solution 
 of the proto-chloride, when this result is desired, 
 should be used much more diluted with water than 
 when it is required for converting negatives into 
 positives. This conversion can be repeated several 
 times, often to the great improvement of the proof. 
 
CHEMICALS USED IN PHOTOGRAPHY. 
 
 119 
 
 (174.) Pyrogallic Acid. (C 6 H 3 0 3 .) 
 
 (Equivalent, 63=C 36 -f- H 3 -f- 0 24 .) 
 
 This powerful developing agent is prepared, 
 according to the formula of Dr. Stenhouse, in the 
 following manner:— 
 
 Make a strong aqueous infusion of powdered 
 nut-galls; pour it off from the undissolved residue, 
 and carefully evaporate to dryness by a gentle heat: 
 towards the conclusion of the process the extract is 
 very liable to burn; this is best prevented by con¬ 
 tinually stirring with a glass or porcelain spatula. 
 Next, procure a flat-bottomed iron pan, about ten 
 inches in diameter, and five inches deep. Make a 
 hat of cartridge-paper about seven inches high, to 
 slip over and accurately fit the top of the iron pan. 
 Strew the bottom of the pan with the gall extract to 
 the depth of three-quarters of an inch; over the top 
 stretch and tie a piece of bibulous paper, pierced 
 with numerous pin-holes; over this place the hat, 
 and tie it also tightly round the top of the pan. 
 
 The whole apparatus is now to be placed in a 
 sand-bath, and heat cautiously applied. It is con¬ 
 venient to place a thermometer in the sand-bath as 
 near the iron pan as possible. The heat is to be 
 continued about an hour, and to be kept as near 
 420° F. as possible: on no account to exceed 450°. 
 The vapour of the acid condenses in the hat, and 
 
120 
 
 CHEMICALS USED IN PHOTOGRAPHY. 
 
 the crystals are prevented from falling back into the 
 pan by the bibulous paper diaphragm. When it is 
 supposed that the whole of the acid is sublimed, the 
 strings are to be untied, and the hat and diaphragm 
 cautiously taken off together; the crystals will be 
 found in considerable quantity, and may be re¬ 
 moved into a stoppered bottle : they should be very 
 brilliant, and perfectly white; if there is any yellow 
 tinge, the heat has been too great. 
 
 Pyrogallic acid dissolves readily in water; the 
 solution is speedily decomposed, becoming black. 
 
 “SIZING” MATERIALS. 
 
 (175.) Starch, Albumin, Gelatine, Wax. 
 
 Starch dissolved in boiling water forms a “ size,” 
 which is afterwards insoluble in cold water; the 
 best for the purposes of photography is obtained 
 from rice (p. 30). 
 
 Starch has a great affinity for iodine, and causes 
 it to abandon most of the bases with which it is 
 united. The iodine colours starch a deep blue, 
 which serves to aid us in recognising its presence 
 in a liquid. Wax has also a similar affinity for 
 iodine. 
 
CHEMICALS USED IN PHOTOGEAPIIY. 
 
 121 
 
 Starch is capable of being converted into a 
 gummy substance called dextrin. A mixture of 
 15 parts of starchy 60 parts water, and 6 parts 
 sulphuric acid, may be kept boiling for about four 
 hours; the liquid neutralised with chalk, filtered, 
 and rapidly evaporated to a small bulk. This sub¬ 
 stance is dextrin, and is sold under the name of 
 British gum. It is a useful substitute for glue, as 
 it is soluble in cold water. 
 
 (176.) A warm solution of gelatine, applied 
 upon paper at the same time with the iodide and 
 other salts, leaves a size which does not dissolve in 
 cold water. 
 
 (177.) Albumin also forms an excellent size, 
 from its property of becoming insoluble in acids 
 and in alcohol by the application of heat (about 
 150°). 
 
 (178.) Collodion applied to paper answers the 
 purpose of a size; but its chief application is to glass, 
 when iodised, to obtain instantaneous impressions. 
 
 This substance has a remarkable effect in form¬ 
 ing the blacks in the proofs, at the same time it is a 
 good size. 
 
 (179.) Wax becomes permeable to liquids after 
 it has remained in a bath containing alkaline salts; 
 
122 
 
 CHEMICALS USED IN PHOTOGKAPHY. 
 
 it forms also an excellent size, and does not exclude 
 the use of others. 
 
 (180.) Alum. —English paper soaked for a few 
 minutes in a strong solution of alum, and afterwards 
 washed in clean water, is in an improved condition 
 for receiving the solution of salts of silver for 
 positives. 
 
 (181.) Sulphate of Pkotoxide of Ikon. 
 
 (Fe O, S O 3 .) 
 
 (Equivalent, 76 = Fe 28 + 4 0 32 -f S 16.) 
 
 This substance is well known under the names 
 of green copperas or green vitriol. It is employed 
 in photography as a means of converting a collodion 
 negative into a positive (124). 
 
DEFINITION 
 
 OF THE 
 
 TECHNICAL TERMS EMPLOYED IN 
 PHOTOGRAPHY. 
 
 (182.) Concentration. —This is a thickening 
 process produced by the action of heat upon solu¬ 
 tions* by which the liquid is evaporated* and the 
 solution becomes more dense* or nearer to the solid 
 state. 
 
 Crystallisation. —Certain bodies* such as salts* 
 in passing from a state of solution to the solid* assume 
 regular forms* which are called crystals. By redis¬ 
 solving these crystals* and again crystallising them* 
 we obtain the crystallised substances in a state 
 of greater purity. 
 
 Decantation. — Solutions* when allowed to stand 
 undisturbed for a certain time* frequently deposit a 
 sediment* from which it is desirable to remove the 
 clear supernatant liquid; this operation* when 
 accomplished by a siphon or pipette* or by gently 
 inclining the vessel so as not to disturb the sediment* 
 is termed Decantation. It sometimes serves the 
 purpose of Filtration. 
 
124 
 
 TECHNICAL TERMS. 
 
 Decomposition.— This action takes place when 
 two compound solutions are mixed, and the con¬ 
 stituents change places ; for instance, when we add 
 sulphuric acid to chloride of barium, the acid seizes 
 upon the barium forming sulphate of barytes, and the 
 chloride is displaced or set free; but when we add 
 nitrate of silver to chloride of barium, double de¬ 
 composition ensues; the chlorine goes to the silver, 
 giving rise to chloride of silver, while the nitric acid 
 combines with the barium, forming nitrate of barytes. 
 
 Diaphragm. —Discs pierced in their centre with 
 round holes of different dimensions, and placed in 
 front of the lenses of the camera, to exclude the 
 excess of light, and to modify the clearness of the 
 image in the focus. They also serve to correct the 
 spherical aberration. 
 
 Evaporation. —Certain volatile substances, such 
 as ether, alcohol, &c., entirely disappear, or evaporate, 
 upon exposure to the atmosphere; so also does 
 water, and other fluids, but more slowly: when 
 these fluids contain solid bodies in solution, they 
 become, by evaporation, concentrated, and finally 
 restore to the solid form the solid held in solution, 
 which is left behind by the removal of the fluid in 
 the state of vapour. 
 
 Proofs, Positives and Negatives. —The im¬ 
 pressions produced by the action of light upon 
 prepared sensitive media are of two kinds. Negatives 
 and Positives. The Negatives are those in which 
 
TECHNICAL TERMS. 
 
 125 
 
 the lights and shadows are reversed* such as are 
 obtained in the camera on paper* albumen* &c. 
 The Negatives obtained upon collodion can be 
 converted into Positives by varying the developing 
 process. 
 
 Positives are those obtained by super-imposing 
 a Negative upon paper prepared for the purpose; 
 producing a reverse effect by the passage of light 
 through the non-darkened portions of the Negative* 
 and yielding a picture resembling* in its light and 
 shade* an engraving; and of various tints* from a 
 light bistre* through various gradations of violet and 
 black. Positives can also be produced at once by 
 employing the proper developing agent. 
 
 Nascent State. —To act upon a substance in 
 its nascent state* is to use it at the moment of 
 its formation* and before the air* or other foreign 
 bo&y, has had time to modify it. 
 
 Precipitation. —A substance held in solution 
 by a liquid is precipitated by adding to the liquid 
 another substance for which it has a greater affinity* 
 through which it leaves the first substance and 
 precipitates it. 
 
 Rectification —Is the operation by which a 
 substance is brought to a greater state of purity; 
 in fluids this is sometimes accomplished by distil¬ 
 lation ; in certain solids by recrystallisation. 
 
 Reduction — Is the operation by which the 
 oxides of metals pass into the metallic state. 
 
126 
 
 TECHNICAL TERMS. 
 
 Solution —Is the dissolving of a solid body in 
 a liquid, such as water, alcohol, &c. Bodies are 
 melted by the action of heat, or by their chemical 
 action upon each other; but these are not solutions , 
 which require a solvent 
 
 Saturation. — Saturated Solution.— Generally 
 speaking, most liquids will only dissolve a certain 
 given quantity of a solid body submitted to their 
 action, varying, however, with the temperature at 
 which the solution is made. Thus, 100 ounces*of 
 water at 60° will dissolve only 36 ounces of muriate 
 of ammonia; if the water is at the boiling point it 
 will dissolve its own weight of the salt; but the 
 excess is deposited again as the water cools down to 
 60°. It requires 143 ounces of iodide of potassium 
 to saturate 100 ounces of water at 65°. Common 
 salt is equally soluble in water at all temperatures. 
 
A FEW PRACTICAL HINTS ON THE 
 COLLODION PROCESS. 
 
 (183.) Ascertain that the frames are accurately 
 adjusted to the focus of the lens. A difference 
 exists between the apparent and the chemical foci 
 of some lenses, which should be adjusted by the 
 maker of the camera, or a clear picture will never 
 be obtained. If an optician is not near who can 
 test this difference, the error that exists may be dis¬ 
 covered by trying upon the same object three or 
 four times; and at each trial, after having focused 
 the object upon the ground-glass, turning the rack 
 of the lens more or less backwards or forwards as 
 may be required. We can thus note where the 
 sharpest impression is obtained. 
 
 Be very careful that the glass plates are per¬ 
 fectly clean; more failures arise from want of care in 
 this respect than from any other causes. 
 
 Keep the nitrate-of-silver bath covered up 
 when not in use. The slightest impurity in it 
 may spoil a good picture. 
 
 Remember that nitrate of silver blackens almost 
 everything it touches. The fingers will soon exhibit 
 stains that no washing can remove, but they will 
 
128 
 
 PRACTICAL HINTS. 
 
 wear off in a few days. If gloves are used when 
 operating with the plate with the nitrate on, and 
 taken off during all other manipulations, no harm 
 will result, and the fingers will be saved; but if 
 gloves are used constantly, and any of the hyposul¬ 
 phite or the pyrogallic acid remain on them, it 
 would be apt to spoil the next plate prepared. 
 Cyanide of potassium will clean the hands at any 
 time, but is a deadly poison, and even the fumes of 
 it are nauseous. It is better not to have recourse 
 to it; a substance called cyanogen soap has lately 
 been introduced for cleaning the hands from these 
 stains. 
 
 Be careful, in weighing or measuring, that the 
 scales or measures are quite clean. After each 
 operation they must be carefully wiped. 
 
 Be sure that no light, except the subdued light 
 of the operating-room, falls upon the plate from 
 the time it is taken from the nitrate bath until after 
 it is developed. Some operators even cover up 
 the slide in a little bag while removing it from the 
 room to the camera. 
 
 It is best to expose the plate in the camera as 
 soon as possible after it leaves the bath; but it 
 may sometimes be necessary to carry it a short dis¬ 
 tance, which must be done as quickly as possible, so 
 as not to allow time for the plate to dry; and 
 upon returning, plunge it again, but for a fraction 
 of a second only, into the nitrate-of-silver bath. 
 
PRACTICAL HINTS. 
 
 129 
 
 If the bath appears impure, drop two or three 
 minims of nitric acid into it, and after a few 
 minutes pour off all the clear liquid into a clean 
 vessel; then rinse out the bath with distilled water, 
 and pour the clear liquid back again. 
 
 Common cistern or river water is full of im¬ 
 purities, which would decompose many salts if 
 dissolved in it. If distilled water cannot be got, 
 clean ice melted produces very pure water; and 
 boiled rain-water, filtered, may do as a substitute. 
 
 The developing solution should always be fil¬ 
 tered, and placed out of the reach of splashes. It 
 will remain useful for many days. 
 
 K 
 
130 
 
 (184.) Weights and Measures. 
 
 Apothecaries' Weight. 
 
 1 grain. 
 
 20 = 1 scruple. 
 
 60 = 3=1 drachm. 
 
 480 = 24 = 8 = 1 ounce. 
 
 5760 = 288 = 96 = 12 = 1 pound. 
 
 Fluid Measure . 
 
 Grains. 
 
 1 minim.= 0*91 
 
 60 = 1 fluid drachm . . . . = 54*7 Avoird. 
 
 480 = 8 = 1 fluid ounce . . = 437*5 = 1 oz. 
 
 9,600= 160 = 20 =1 pint. . .= 8,750 =1*2511). 
 
 76,800 = 1280 = 160 = 8 = 1 gallon = 70,000 = 10 lbs. 
 
 One Pound Avoirdupois . . contains . 
 One Pound Troy .... „ 
 
 One Imperial Gallon of Water „ 
 
 One Imperial Pint of Water „ 20 oz. 
 
 . 7,000 
 . 5,760 
 . 70,000 
 or 8,750 
 
 grains 
 
 77 
 
 7? 
 
 77 
 
 One Cubic Inch of Water 
 One Ounce Avoirdupois . 
 One Ounce Troy . . . 
 One Gramme . 
 
 252*4 
 
 437*5 
 
 480 
 
 15*4 
 
 w 
 
 ?? 
 
 77 
 
 One Decigramme . . . 
 
 One Litre of Distilled Water 
 
 1*5 
 
 15,406*3 
 
 ?? 
 
 77 
 
 *** The grain is the unit of weight; but as three standards of weight are 
 employed, much uncertainty and confusion often arise in the mind of the 
 photographer as to which ounce or drachm is meant. The apothecaries’ 
 weight is generally understood to be the one employed ; but it would save 
 much trouble if the formula for the various preparations were always given 
 in grains. 
 
APPENDIX. 
 

 
 
PROCESSES ON PAPER. 
 
 1.—Iodising the Paper * 
 
 Take a sheet of the best writing-paper, having a smooth Mr. Talbot’s 
 
 surface, and a close and even texture ; the water-mark, if pioce * s 
 
 any, should be cut off, lest it should injure the appearance 
 
 of the picture. Dissolve 100 grains of crystallised nitrate 
 
 of silver in six ounces of distilled water. Wash the paper 
 
 with this solution with a soft brush on one side, and put a 
 
 mark on that side whereby to know it again. Dry the 
 
 paper cautiously at a distance from the fire, or else let it 
 
 dry spontaneously in a dark room. When dry, or nearly 
 
 so, dip it into a solution of iodide of potassium, containing 
 
 500 grains of that salt dissolved in one pint of water, and 
 
 let it stay two or three minutes in the solution. Then dip 
 
 the paper into a vessel of water, dry it lightly with blotting- 
 
 paper, and finish drying it at a fire, which will not injure 
 
 it, even if held pretty near ; or else it may be left to dry 
 
 spontaneously. All this is best done in the evening by 
 
 candle-light: the paper, so far prepared, is called iodised 
 
 paper , because it has a uniform pale yellow coating of iodide 
 
 of silver. It is scarcely sensitive to light, but nevertheless 
 
 it ought to be kept in a portfolio, or drawer, until wanted 
 
 for use. 
 
 The calotype paper is rendered more sensitive by placing 
 a warm iron behind it in the camera whilst the light is 
 acting upon it. 
 
 Io-gallic paper is prepared by washing a sheet of iodised 
 paper with gallic acid. In this state it will keep in a 
 
 * It has since been found a better method to iodise the paper 
 previous to applying the nitrate of silver. 
 
134 
 
 APPENDIX. 
 
 Iodising the 
 Paper. 
 
 portfolio, and is rendered sensitive to light by washing it 
 over with a solution of nitrate of silver. 
 
 Iodised paper is washed with a mixture of twenty-six 
 parts of a saturated solution of gallic acid to one part of the 
 solution of nitrate of silver ordinarily used. It can then be 
 dried without fear of spoiling, may be kept a little time, 
 and used without further preparation. 
 
 Mr. H. Cun- 
 dell’s pro¬ 
 cess. 
 
 Much depends upon the paper selected for the purpose ; 
 it must be of a compact and uniform texture, smooth and 
 transparent, and of not less than medium thickness. The 
 best I have met with is a fine satin post paper made by 
 “R. Turner, Chafford Mill.” Having selected a half sheet 
 without flaw or watermark, and free from, even the minutest, 
 black specks, the object is to spread over its surface a 
 perfectly uniform coating of the iodide of silver, by the 
 mutual decomposition of two salts, nitrate of silver and 
 iodide of potassium. There is a considerable latitude in 
 the degree of dilution in which these salts may be used, 
 and also in the manner and order of their application ; but 
 as the thickness and regularity of the coating depend upon 
 the solution of nitrate of silver, and upon the manner in 
 which it is applied, I think it ought, by all means, to be 
 applied first, before the surface of the paper is disturbed. 
 I use a solution of the strength of seventeen grains to the 
 ounce of distilled water. 
 
 The paper may be pinned by its two upper corners to a 
 clean dry board a little larger than itself; and holding this 
 nearly upright in the left hand, and commencing at the top, 
 apply a wash of the nitrate of silver thoroughly , evenly , and 
 smoothly , with a large soft brush, taking care that every 
 part of the surface be thoroughly wetted, and that nothing 
 remain unabsorbed in the nature of free or running solution. 
 
 Let the paper now hang loose from the board into the air 
 to dry, and by using several boards time will be saved. 
 
 The nitrate of silver spread upon the paper is now to be 
 saturated with iodine, by bringing it in contact with a 
 
APPENDIX. 
 
 135 
 
 solution of the iodide of potassium ; the iodine goes to the Iodising the 
 silver, and the nitric acid to the potash. Paper. 
 
 Take a solution of the iodide of potassium of the 
 strength of 400 grains to the pint of water, to which it is 
 an improvement to add 100 grains of common salt. Pour 
 the solution into a shallow, flat-bottomed dish, sufficiently 
 large to admit the paper, and let the bottom of the vessel 
 be covered to the depth of one-eighth of an inch. The 
 prepared side of the paper, having been previously marked, 
 is to be brought in contact with the surface of the solution; 
 and as it is desirable to keep the other side clean and dry, 
 it will be found convenient, before putting it in the iodine, 
 to fold upwards a narrow margin along the two opposite 
 edges. Holding by the upturned margin, the paper is to be 
 gently drawn along the surface of the liquid until its lower 
 face be thoroughly wetted in every part; it will become 
 plastic, and in that state may be suffered to repose for a 
 few moments in contact with the liquid: it ought not, 
 however, to be exposed in the iodine dish for more than a 
 minute altogether, as the new compound, just formed upon 
 the paper, upon further exposure, would be gradually re¬ 
 dissolved. The paper is, therefore, to be removed ; and 
 after dripping, it may be placed upon any clean surface 
 with the wet side uppermost, until about half dry, by which 
 time the iodine solution will have thoroughly penetrated 
 the paper, and have found out and saturated every particle 
 of the silver ; which it is quite indispensable it should do, 
 as the smallest particle of undecomposed nitrate of silver 
 would become a black stain in a subsequent part of the 
 process. 
 
 The paper is now covered with a coating of the iodide 
 of silver ; but it is also covered, and indeed saturated, with 
 saltpetre and the iodide of potassium, both of which it is 
 indispensable should be completely removed. To effect the 
 removal of these salts, it is by no means sufficient to dip 
 the paper in water ; neither is it a good plan to wash the 
 paper with any considerable motion, as the iodide of silver, 
 
136 
 
 APPENDIX. 
 
 Iodising the 
 Paper 
 
 Mr. Bing¬ 
 ham’s 
 method. 
 
 Mr. Chan- 
 
 ning’s 
 
 method. 
 
 having but little adhesion to it, is apt to be washed off. 
 But the margin of the paper being still upturned, and the 
 unprepared side of it kept dry, it will be found that by 
 setting it afloat on a dish of clean water, and allowing it to 
 remain for five or ten minutes, drawing it gently, now and 
 then, along the surface to assist in removing the soluble 
 salts ; these will separate by their own gravity, and (the 
 iodide of silver being insoluble in water) nothing will 
 remain upon the paper but a beautifully perfect coating of 
 the kind required. 
 
 The paper is now to be dried; but while wet, do not, 
 on any account, touch or disturb the prepared surface with 
 blotting-paper or with anything else. Let it merely be 
 suspended in the air, and in the absence of a better expedi¬ 
 ent, it may be pinned across a string by one of its corners : 
 when dry, it may be smoothed by pressure. It is now 
 “ iodised ” and ready for use, and in this state will keep 
 any length of time if protected from the light. 
 
 Apply to the paper a solution of nitrate of silver 
 containing 100 grains of that salt to one ounce distilled 
 water. When nearly, but not quite dry, dip it into a 
 solution of iodide of potassium of the strength of 25 
 grains of that salt to 1 ounce of distilled water, drain it, 
 wash it, and then allow it to dry. Now brush it over 
 with aceto-nitrate of silver, made by dissolving 50 grains 
 nitrate of silver in 1 ounce distilled water, to which is 
 added one-sixth its volume of acetic acid. Dry it with 
 bibulous paper, and it is now ready for receiving the image. 
 
 The paper should be first washed over with 60 grains 
 of nitrate of silver dissolved in 1 ounce distilled water, 
 and when dry, with a solution of 10 grains of iodide of 
 potassium in 1 ounce water ; it is then to be washed in 
 water, and dried between folds of blotting-paper: the 
 sensibility of the paper is said, and correctly, to be much 
 improved by combining a little chloride of sodium with 
 
APPENDIX. 
 
 137 
 
 the iodide of potassium, 5 grains of the latter salt, and Iodising the 
 rather less than this of the former, in an ounce of water, Fafer 
 may be employed advantageously. 
 
 To use this paper where time is an object, it is necessary 
 to wash it immediately before it is placed in the camera, 
 with a weak solution of nitrate of silver, to which a drop or 
 two only of gallic acid has been added. The picture is 
 subsequently developed by the gallo-nitrate of silver. 
 
 Iodide of silver is precipitated from the solution of the Mi\ Jordan’s 
 nitrate by iodide of potassium, and this precipitate, being 
 lightly washed, is redissolved in a strong solution of the 
 latter salt. The solution is applied to the paper, and the 
 paper allowed to dry : after this it is placed, face down¬ 
 wards, upon some clean water ; the iodide of potassium is 
 removed by this, and a pure iodide of silver left upon the 
 paper. 
 
 M. Martens uses spirits of wine after the picture has M. Martens’ 
 been developed, to improve its tone. 
 
 For the negative picture : 
 
 First,— 
 
 Iodine of potassium . \ oz. 
 
 Distilled water.10 
 
 Concentrated solution of cyanide of potassium 7 drops. 
 Second,— 
 
 Nitrate of silver .... 7 drachms 
 
 Distilled water.10 oz. 
 
 Strong acetic acid ... 2 drachms. 
 
 The iodine solution should be applied first, and dried ; 
 then the argentine solution, and dried rapidly : the advan¬ 
 tages of this are, that the iodide of silver is left on the 
 
138 
 
 APPENDIX. 
 
 Iodising the 
 Papeb. 
 
 M. Le Gray’s 
 process. 
 
 surface of the paper ready for the influence of the slightest 
 chemical action. 
 
 Third,— 
 
 A concentrated solution of gallic acid. 
 
 Fourth,— 
 
 Good spirits-of wine. 
 
 Fifth,— 
 
 Hyposulphite of soda .... 1 oz. 
 
 Distilled water.10 „ 
 
 For the positive pictures : 
 
 First,— 
 
 Chloride of sodium .... 168 grains 
 
 Distilled water.10 oz. 
 
 Second,— 
 
 Nitrate of silver.1 oz. 
 
 Distilled water.10 „ 
 
 Third,— 
 
 Hyposulphite of soda .... 1 oz. 
 
 Distilled water.10 „ 
 
 Nitrate of silver 30 grains, dissolved in Joz. of 
 water, to be poured into the solution in a small 
 stream, while it is constantly stirred with a 
 glass rod. 
 
 For negatives: 
 
 First operation,— 
 
 Isinglass, 300 grains, dissolved in 1 j pint of distilled 
 water by means of a water-bath. 
 
 Take one-half of this preparation while warm, and add 
 to it as under,— 
 
 Iodide of potassium . . . 200 grains 
 Bromide of potassium . . 60 „ 
 
 Chloride of sodium ... 34 „ 
 
APPENDIX. 
 
 139 
 
 Let these salts be well dissolved, then filter the solution Iodising the 
 through a piece of linen ; put it, still warm, in a large dish, — * 
 and plunge in your paper completely, leaf by leaf, one on 
 the other, taking care to prevent the air-bubbles from 
 adhering to the paper. 
 
 Put about twenty leaves at a time into the dish, then 
 turn the whole, those at the top to the bottom ; then take 
 them out one by one, and hang them by one corner with a 
 pin bent like the letter S, to dry spontaneously. When 
 hung up, attach to the opposite corner a piece of bibulous 
 paper, which will facilitate the drying. 
 
 When the paper is dry, cut it to the size required, and 
 preserve it in a folio for use. This paper may be made in 
 the day-time, as it is not sensitive to light. 
 
 Second operation,— 
 
 Prepare, by the light of a taper, the following solution 
 in a stoppered bottle : 
 
 Nitrate of silver .... 250 grains 
 Distilled water. 6 fl. ounces 
 
 When the nitrate is dissolved, add, 
 
 Crystallisable acetic acid. . 1 ounce 
 
 Cover the bottle with black paper, and keep it from the 
 light. 
 
 When you wish to operate, pour the solution upon a 
 porcelain or glass slab, having a border of glass or wax; 
 take a sheet of the iodised paper by the two corners, 
 holding them perpendicularly, and gently lower the middle 
 of the paper upon the centre of the slab, gradually depress 
 until the sheet is equally spread : repeat this operation 
 several times until the air-bubbles disappear, taking also 
 the precaution to keep the upper side of the paper dry. 
 
 Let the sheet remain upon the slab until the formation of 
 the chloro-bromo-iodide of silver is perfect. This may be 
 
140 
 
 APPENDIX. 
 
 Iodising the 
 Paper. 
 
 Mr. Thomas’s 
 method. 
 
 known by the disappearance of the violet colour, which 
 the back of the paper at first presented: it must not be 
 left longer, otherwise it would lose its sensitiveness. The 
 time required to effect this chemical change is from one to 
 five minutes, depending upon the quality of the paper. 
 
 Spread upon a glass, fitted to the frame of the camera, 
 a piece of white paper well soaked in water; upon this 
 place the prepared sheet, the sensitive side upwards. 
 
 Select old and thin English paper—I prefer What¬ 
 man’s—and cut it to the size of the frames. Prepare the 
 following solution,— 
 
 Saturated solution of iodide of potassium 2^ fl.drachms 
 
 Pure iodine.9 grains. 
 
 Dissolve, then add,— 
 
 Distilled water.11J oz. 
 
 Iodide of potassium.4 drachms 
 
 Bromide of potassium.10 grains, 
 
 and mix. Filter the mixture into a shallow porcelain 
 vessel, and place a sheet of paper carefully on the surface 
 of the fluid, and let it remain about two minutes ; if 
 French paper, one minute, or until the iodine tint shows 
 through the paper, which must not be wetted at the back. 
 Hang it up by one corner to drain and dry. 
 
 To excite this paper, lay it upon a solution of 
 
 Nitrate of silver.2J drachms 
 
 Acetic acid.4^ „ 
 
 Distilled water.3J oz. 
 
 This paper is used in the camera by the wet method, 
 p. 48. 
 
 The object was taken by an achromatic lens of three 
 inches diameter, and half-inch diaphragm; and, if well 
 lighted by the sun, in from four to six minutes’ exposure. 
 
APPENDIX. 
 
 141 
 
 The image takes from ten to twenty minutes to deve- Exciting 
 
 lope in a solution of gallic acid. It may be fixed in the _ 
 
 usual manner by the hyposulphite of soda, or by a solution 
 of bromide of potassium, ten grains to the ounce of water. 
 
 2.—Exciting the Paper for the Camera. 
 
 For this purpose are required two solutions, as de- Mr. H. Cun- 
 scribed by Mr. Talbot,—viz. a saturated solution of crys- cess. Spr °" 
 tallised gallic acid in cold distilled water, and a solution of 
 nitrate of silver, of the strength of fifty grains to the ounce 
 of distilled water; to which is added one-sixth part of its 
 volume of glacial acetic acid. For many purposes these 
 solutions are unnecessarily strong, and, unless skilfully 
 handled, they are apt to stain or embrown the paper; 
 where extreme sensitiveness, therefore, is not required, 
 they may with advantage be diluted to half the strength, 
 in which state they are more manageable, and nearly as 
 effective. The gallic-acid solution will not keep for more 
 than a few days, and only a small quantity, therefore, 
 should be prepared at a time. When these solutions are 
 about to be applied to the iodised paper, they are to be 
 mixed together in equal volumes, by means of a graduated 
 drachm tube. The mixture is called “ the gallo-nitrate of 
 silver.” As it speedily changes, and will not keep more 
 than a few minutes, it must be used without delay ; and it 
 ought not to be prepared until the operator is quite ready 
 to apply it. 
 
 The application of this “ gallo-nitrate ” to the paper is 
 a matter of some nicety. It will be found best to apply it 
 in the following manner:—Pour out the solution upon a 
 clean slab of plate-glass, diffusing it over the surface to a 
 size corresponding to that of the paper : holding the paper 
 by a narrow, upturned margin, the sensitive side is to be 
 applied to the liquid upon the slab, and brought in 
 
142 
 
 APPENDIX. 
 
 he Paper con ^ ac ^ with it by passing the fingers gently over the 
 — back of the paper, which must not be touched with the 
 solution. 
 
 As soon as the paper is wetted with the gallo-nitrate, it 
 ought instantly to be removed into a dish of water: five or 
 ten seconds at the most is as long as it is safe, at this stage, 
 to leave the paper to be acted upon by the gallo-nitrate; 
 in that space of time it absorbs sufficient to render it 
 exquisitely sensitive. The excess of gallo-nitrate must 
 immediately be washed off, by drawing the paper gently 
 several times under the surface of water, which must be 
 perfectly clean ; and, being thus washed, it is finished by 
 drawing it again through fresh water two or three times. 
 It is now to be dried in the dark, and, when the surface is 
 dry, it may either be placed, while still damp, in the camera, 
 or in a portfolio among blotting-paper, for use. If pro¬ 
 perly prepared, it will keep perfectly well for four-and- 
 twenty hours at least, retaining all its whiteness and 
 sensibility. 
 
 3.—Exposure in the Camera. 
 
 Mr. Cundell’s 
 process. 
 
 The exposure in the camera, for which, as the operator 
 must be guided by his own judgment, few directions can be 
 given, and few are required. He must choose or design 
 his own subject: he must determine upon the aperture to 
 be used, and judge of the time required, which will vary 
 from a few seconds to three or four minutes. The subject 
 ought, if possible, to have a strong and decided effect; 
 but extreme lights, or light-coloured bodies, in masses, are 
 by all means to be avoided. When the paper is taken 
 from the camera, very little or no trace whatever of a 
 picture is visible, until it is subjected to the fourth process, 
 which is— the Bringing out of the Picture. 
 
APPENDIX. 
 
 143 
 
 Bringing 
 out the Pic- 
 
 4.—Bringing out the Picture. ture - 
 
 The developement of the picture is effected by again Mr. H. Cun 
 applying the “ gallo- nitrate ” as before directed (p. 40). method. 
 
 As soon as the paper is wetted all over, unless the 
 picture appears immediately, it is to be exposed to the 
 radiant heat from a smoothing iron, or any similar body ? 
 held within an inch or two by an assistant. It ought to be 
 held vertically, as well as the paper ; and the latter ought 
 to be moved so as to prevent any one part of it becoming 
 dry before the rest. 
 
 As soon as the picture is sufficiently brought out, wash 
 it immediately in clean water to remove the gallo-nitrate, 
 as directed in (p. 40) ; it may then be placed in a dish 
 by itself, under water, until you are ready to fix it. 
 
 The most perfect pictures are those which come out before 
 any part of the paper becomes dry, which they will do if 
 sufficiently impressed in the camera. If the paper be 
 allowed to dry before washing off the gallo-nitrate, the lights 
 sink and become opaque ; and if exposed in the dry state 
 to heat, the paper will embrown ; the drying, therefore, 
 ought to be retarded , by wetting the back of the paper, 
 or the picture may be brought out by the vapour from hot 
 water, or, what is better, from a horizontal jet of steam. 
 
 5.— Fixing the Picture, 
 
 The fixing of the picture is accomplished by removing Mr.^H. Cun ’ 
 the sensitive matter from the paper. The picture, or as method, 
 many of them as there may be, is to be soaked in warm 
 water, but not warmer than may be borne by the finger; 
 this water is to be changed once or twice, and the pictures 
 are then to be well drained, and either dried all together, or 
 pressed in clean dry blotting-paper, to prepare them to 
 imbibe a solution of the hyposulphite of soda, which may 
 be made by dissolving an ounce of that salt in a quart of 
 
144 
 
 APPENDIX. 
 
 Fixing the 
 Picture. 
 
 Mr. H. Cun- 
 
 dell’s 
 
 method. 
 
 water. Having poured a little of the solution into a flat 
 dish, the pictures are to be introduced into it one by one ; 
 daylight will not now injure them: let them soak for 
 two or three minutes, or even longer, if strongly printed, 
 turning and moving them occasionally. The remaining 
 unreduced salts of silver are thus thoroughly dissolved, and 
 may now, with the hyposulphite, be entirely removed by 
 soaking in water, and pressing in clean white blotting-paper, 
 alternately ; but if time can be allowed, soaking in water 
 alone will have the effect in twelve or twenty-four hours, 
 according to the thickness of the paper. 
 
 It is essential to the success of the fixing process that 
 the paper be, in the first place, thoroughly penetrated by 
 the hyposulphite, and the sensitive matter dissolved : and 
 next that the hyposulphite compounds be effectually 
 removed. Unless these salts are completely removed, they 
 induce a destructive change upon the picture, they become 
 opaque in the tissue of the paper, and entirely unfit it for 
 the next, or printing process. 
 
 6.—The Printing Process. 
 
 The picture being thus fixed, it has merely to be dried 
 and smoothed, when it will undergo no further change. It 
 is, however, a negative picture, and if it have cost some 
 trouble to produce it, that trouble ought not to be grudged, 
 considering that you are now possessed of a matrix which 
 is capable of yielding a vast number of beautiful im¬ 
 pressions. 
 
 The manner of obtaining these impressions has been so 
 often described, and there are so many different modes of 
 proceeding, that it may be sufficient to notice very briefly 
 the best process with which I am acquainted. Photography 
 is indebted for it to Dr. Alfred S. Taylor. This solution is 
 made by dissolving one part of nitrate of silver in twelve of 
 distilled water, and gradually adding strong liquid ammonia 
 
APPENDIX. 
 
 145 
 
 until the precipitate at first produced is at length just re- Various 
 ,. , . Methods. 
 
 dissolved. — 
 
 Some paper is to be met with containing traces of 
 bleaching chlorides, which does not require any previous 
 preparation ; but in general it will be found necessary to 
 prepare the paper by slightly impregnating it with a minute 
 quantity of common salt. This may be done by dipping it 
 in a solution in which the salt can scarcely be tasted, or of 
 the strength of from thirty to forty grains to a pint of 
 water. The paper, after being pressed in clean blotting- 
 paper, has merely to be dried and smoothed, when it will 
 be fit for use. 
 
 The ammonio-nitrate of silver is applied to the paper in 
 the manner described in Section 3; and when perfectly dry 
 the negative picture to be copied is to be applied to it, with 
 its face in contact with the sensitive side. The back of the 
 negative picture being uppermost, they are to be pressed 
 into close contact by means of a plate of glass; and thus 
 secured, they are to be exposed to the light of the sun and 
 sky. The exposed parts of the sensitive paper will speedily 
 change to lilac, slate-blue, deepening towards black; and 
 the light gradually penetrating through the semi-transparent 
 negative picture, will imprint upon the sensitive paper be¬ 
 neath a positive impression. The negative picture, or matrix, 
 being slightly tacked to the sensitive paper by two mere 
 particles of wafer, the progress of the operation may from 
 time to time be observed, and stopped at the moment when 
 the picture is finished. 
 
 It ought, then, as soon as possible, to be soaked in warm 
 water, and fixed in the manner described in Section 14. 
 
 Prepare the paper by floating it in a solution of fifteen Mr. Miller’s 
 grains of nitrate of lead in an ounce of water. It is then process - 
 placed on a solution of ten grains of iodide of iron to an 
 ounce of water; left two minutes and blotted off. The 
 paper, while moist, is rendered sensitive by a solution of 
 nitrate of silver, 100 grains to an ounce of water, and placed 
 
 L 
 
146 
 
 APPENDIX. 
 
 Methods * n a camera • After exposures the image gradually deve- 
 — ’ lopes itself without any further application, and is fixed by 
 hyposulphite of soda. This is a most striking discovery, as 
 it supersedes the necessity of any developing agent after 
 the light has acted on the paper. 
 
 Mr. Stewart’s The following observations are confined to negative 
 paper processes, divisible into two—the wet and the dry . 
 The solutions I employ for both these processes are iden¬ 
 tical, and are as follows :— 
 
 Solution of iodide of potassium, of the strength of 5 
 parts of iodide to 100 of pure water. 
 
 Solution of aceto-nitrate of silver, in the following pro¬ 
 portions : 15 parts of nitrate of silver; 20 of glacial 
 acetic acid ; 150 of distilled water. 
 
 Solution of gallic acid, for developing; a saturated 
 solution. 
 
 Solution of hyposulphite of soda ; of the strength of one 
 part hypo, of soda to from 6 to 8 parts water. 
 
 The solutions employed are thus reduced to their simplest 
 possible expression, for it will be observed that in iodizing I 
 employ neither rice-water, sugar of milk, fluoride, cyanuret, 
 nor free iodide, &c. &c.; but a simple solution of iodide of 
 potassium. [The strength of this solution is a question of 
 considerable importance, not yet, I think, sufficiently in¬ 
 vestigated.] 
 
 For both the wet and the dry processes I iodize my 
 paper as follows :—In a tray containing the above solution 
 I plunge, one by one, as many sheets of paper (twenty, 
 thirty, fifty, &c.) as are likely to be required for some time. 
 This is done in two or three minutes. I then roll up 
 loosely the whole bundle of sheets, while in the bath ; and 
 picking up the roll by the ends, drop it into a cylindrical 
 glass vessel with a foot to it, and pour the solution therein, 
 enough to cover the roll completely (in case it should float 
 up above the surface of the solution, a little piece of glass 
 
APPENDIX. 
 
 147 
 
 may be pushed down to rest across the roll of paper and Various 
 J ^ x n o . Methods. 
 
 prevent its rising). The vessel with the roll of paper is - 
 
 placed under the receiver of an air-pump, and the air ex- process™ 1 S 
 hausted ; this is accomplished in a very few minutes, and 
 the paper may then be left five or six minutes in the 
 vacuum. Should the glass be too high (the paper being in 
 large sheets) to be inserted under a pneumatic pump- 
 receiver, a stiff lid lined with India-rubber, with a valve in 
 the centre communicating by a tube with a common di¬ 
 rect-action air-pump, may be employed with equal success. 
 
 After the paper is thus soaked in vacuo it is removed, and 
 the roll dropped back into the tray with the solution, and 
 then, sheet by sheet, picked off and hung up to dry, when, 
 as with all other iodized paper, it will keep for an indefinite 
 time. 
 
 I cannot say that I fully understand the rationale of the 
 action of the air-pump, but several valuable advantages are 
 obtained by its use :—1st. The paper is thoroughly iodized, 
 and with an equality throughout that no amount of soaking 
 procures, for no two sheets of paper are alike, or even one, 
 perfect throughout in texture ; and air-bulbs are impossible. 
 
 2d. The operation is accomplished in a quarter of an hour, 
 which generally employs one, two, or more hours. 3d. To 
 this do I chiefly attribute the fact that my paper is never 
 solarized even in the brightest sun; and that it will bear 
 whatever amount of exposure is necessary for the deepest 
 and most impenetrable shadows in the view, without injury 
 to the bright lights. 
 
 Wet Process .—To begin with the wet process. Having Wet process, 
 prepared the above solution of aceto-nitrate of silver, float 
 a sheet of the iodized paper upon the surface of this sensitive 
 bath, leaving it there for about ten minutes. During this 
 interval, having placed the glass or slate of your slider quite 
 level, dip a sheet of thick clean white printing (unsized) 
 paper in water, and lay it on the glass or slate as a wet 
 lining to receive the sensitive sheet. An expert manipulator 
 
148 
 
 APPENDIX. 
 
 Various 
 
 Methods. 
 
 Mr. Stewart’s 
 process. 
 
 Dry process. 
 
 may then, removing the sensitive sheet from the bath, ex¬ 
 tend it (sensitive side uppermost) on this wet-paper lining, 
 without allowing any air-globules to intervene. But it is 
 difficult, and a very simple and most effectual mode of 
 avoiding air-globules, particularly in handling very large 
 sheets, is as follows :—Pour a layer of water (just sufficient 
 not to flow over the sides) upon the lining paper, after you 
 have extended it on your glass or slate, and then lay down 
 your sensitive paper gently and by degrees, and floating as 
 it were on this layer of water; and when extended, taking 
 the glass and papers between the finger and thumb, by an 
 upper corner, to prevent their slipping, tilt it gently to 
 allow the interposed water to flow off by the bottom, which 
 will leave the two sheets of paper adhering perfectly and 
 closely, without the slightest chance of air-bubbles;—it 
 may then be left for a minute or two, standing upright in 
 the same position, to allow every drop of water to escape; 
 so that when laid flat again or placed in the slider none 
 may return back and stain the paper. Of course, the sen¬ 
 sitive side of the sheet is thus left exposed to the uninter¬ 
 rupted action of the lens, no protecting plate of glass being 
 interposed,—and even in this dry and warm climate I find 
 the humidity and the attendant sensitiveness fully preserved 
 for a couple of hours. 
 
 To develope views thus taken, the ordinary saturated 
 solution of gallic acid is employed, never requiring the ad¬ 
 dition of nitrate of silver; thus preserving the perfect 
 purity and varied modulation of the tints. The fixing is 
 accomplished as usual with hyposulphite of soda, and the 
 negative finally waxed. 
 
 Dry Process .—In preparing sheets for use when dry for 
 travelling, &c., I have discarded the use of 'previously waxed 
 paper, thus getting rid of a troublesome operation,—and 
 proceed as follows :—Taking a sheet of my iodized paper, 
 in place of floating it (as for the wet process) on the sen¬ 
 sitive bath, I plunge it fairly into the bath, where it is left 
 
APPENDIX. 
 
 149 
 
 to soak for five or six minutes ; then removing it, wash it Various 
 
 for about twenty minutes in a bath, or even two, of dis- _1 
 
 tilled water, to remove the excess of nitrate of silver, and profess^ 1 " 1, 
 then hang it up to dry (in lieu of drying it with blotting- 
 paper). Paper thus prepared possesses a greater degree of 
 sensitiveness than waxed paper, and preserves its sensitive¬ 
 ness, not so long as waxed paper, but sufficiently long for 
 all practical purposes,—say thirty hours, and even more. 
 
 The English manufactured paper is far superior for this 
 purpose to the French. To develope these views, a few 
 drops of the solution of nitrate of silver are required in the 
 gallic acid bath. They are then finally fixed and waxed as 
 usual. 
 
 These processes appear to me to be reduced to nearly 
 as great a degree of simplicity as possible. I am never 
 troubled with stains or spots, and there is a regularity and 
 certainty in the results that are very satisfactory. You 
 will have observed, too, how perfectly the aerial perspective 
 and gradation of tints are preserved—as also how well the 
 deepest shadows are penetrated and developed—speaking, 
 in fact, as they do to the eye itself in nature. In ex¬ 
 posing for landscape, I throw aside all consideration of 
 the bright lights, and limit the time with reference en¬ 
 tirely to the dark and feebly-lighted parts of the view ; with 
 a 31-inch lens : the time of exposure has thus varied from 
 ten minutes to an hour and a half, and the action appears 
 to me never to have ceased. 
 
 The influence of the air-pump in this appears to me 
 very sensible, and deserving of further examination and 
 extension. I purpose not only iodizing, but rendering the 
 paper sensitive with the action of the air-pump, by perhaps 
 suspending the sheet after immersion in the nitrate bath 
 under the receiver of the air-pump for a few minutes, 
 before exposure in the camera, or by some other manoeuvre 
 having the same object in view. 
 
 I should add, that I have chiefly employed Canson’s 
 French paper in iodizing with the aid of the pump. Few 
 
150 
 
 APPENDIX. 
 
 Various 
 
 Methods. 
 
 Mr. Stewart’* 
 process. 
 
 Sir William 
 
 Newton’s 
 
 method. 
 
 of the English manufactured papers are sufficiently tena¬ 
 cious in their sizing to resist the action of the pump, but 
 they may easily be made so ; and were, in short, the English 
 paper, so far superior in quality to the French, only better 
 sized, that is with glue less easily soluble, even though 
 more impure , there is scarcely any limit to the beauty of 
 the views that might be produced. 
 
 There are more minor details that might be given ; but 
 I fear repeating many a “twice-told tale,” acquainted so 
 little as I am with what is doing;—the preceding, however, 
 may have some interest, and whatever is of value is entirely 
 due to our friend M. Regnau.lt, ever so generously ready as 
 well as able to aid and encourage one’s efforts. 
 
 Negatives , on paper prepared with iodide of silver, 20 
 grains to one ounce of distilled water. 
 
 Excited for the camera (weak), containing about two 
 grains of nitrate of silver to one ounce of water. 
 
 Exposure to the objects from 5 to 15 minutes, according 
 to the subject and weather. 
 
 Waxed afterwards. 
 
 Positives , on negative paper, containing from 7 to 10 
 grains of iodide of silver to one ounce of distilled water. 
 
 Brought out in the same manner as the negatives, with 
 a saturated solution of gallic acid, and finished with 5 grains 
 of aceto-nitrate to one ounce of water. 
 
 Excited with 5 grains of aceto-nitrate to one ounce of 
 water, and exposed to the light in a frame five seconds to 
 half a minute, according to the light and transparency of 
 the negative. 
 
 LondonPrinted by G. Barclay, Castle St. Leicester Sq. 
 
Now Ready, price 165. 
 
 PHOTOGRAPHIC STUDIES. 
 
 By GEORGE SHAW, Esq. 
 
 OF QUEEN’S COLLEGE, BIRMINGHAM. 
 
 Comprising 
 
 A MILL-STREAM A RUSTIC BRIDGE 
 
 A FOREST SCENE A WELSH GLEN. 
 
 These Pictures are of large size, and are very carefully Printed. 
 Part II. will shortly he Published. 
 
 Preparing for Publication, in Parts, price 215. each, 
 
 THE 
 
 PROGRESS OF THE CRYSTAL PALACE 
 AT SYDENHAM. 
 
 Exhibited in a Series of Photographic Views taken 
 by Philip DelaMotte. 
 
 This Work will he found of much service to Engineers and Architects, 
 and all who are interested in the Crystal Palace. 
 
 *** Some of these Views may be had for the Stereoscope. 
 
 Preparing for Publication , 
 
 A SERIES OF PHOTOGRAPHIC PICTURES. 
 
 By HUGH OWEN, Esq. (of Bristol.) 
 
 A SERIES OF PHOTOGRAPHIC 
 
 PICTURES OF WELSH SCENERY. 
 
 By J. D. LLEWELLYN, Esq. 
 
Published in Parts, price 10s. 6d. each, 
 
 THE PHOTOGRAPHIC ALBUM. 
 
 CONTENTS: 
 
 Part I. 
 
 OLD WELL WALK. By Roger Fenton. 
 
 THE VILLAGE STOCKS. By Roger Fenton. 
 TEWKESBURY ABBEY. By Roger Fenton. 
 
 THE OLD BARN. By Roger Fenton. 
 
 Part II. 
 
 PLOUGH INN, PRESTBURY. By Roger Fenton. 
 
 AN ITALIAN BOY. By Philip DelaMotte. 
 
 PITTVILLE SPA. By Roger Fenton. 
 
 OLD BEEHIVES. By Philip DelaMotte. 
 
 Part III. 
 
 TINTERN ABBEY. By Roger Fenton. 
 
 THE BOY IN THE ARCH. By Philip DelaMotte. 
 BURNHAM BEECHES. By Roger Fenton. 
 
 KENILWORTH CASTLE. By Philip DelaMotte. 
 
 Part IV. 
 
 ELM TREE IN UMBERSLEY PARK. By Alfred Rosling. 
 PENSHURST CASTLE. By Philip DelaMotte. 
 
 THE RUINED FARM. By Hugh Owen. 
 
 THE VILLAGE ELM. By Joseph Cundall. 
 
 *** Photographers desirous of contributing to this work arfe 
 requested to address a letter to the Publisher. 
 
 LONDON: 
 
 JOSEPH CUNDALL, 168 NEW BOND STREET. 
 
* 
 
 
 
 / 
 
Published in Parts , price 10s. 6d. each, 
 
 THE PHOTOGRAPHIC ALBUM. 
 
 CONTENTS: 
 
 Part I. 
 
 OLD WELL WALK. By Roger Fenton. 
 
 THE VILLAGE STOCKS. By Roger Fenton. 
 TEWKESBURY ABBEY. By Roger Fenton. 
 
 THE OLD BARN. By Roger Fenton. 
 
 Part II. 
 
 PLOUGH INN, PRESTBURY. By Roger Fenton. 
 
 AN ITALIAN BOY. By Philip DelaMotte. 
 
 PITTVILLE SPA. By Roger Fenton. 
 
 OLD BEEHIVES. By Philip DelaMotte. 
 
 Part III. 
 
 TINTERN ABBEY. By Roger Fenton. 
 
 THE BOY IN THE ARCH. By Philip DelaMotte. 
 BURNHAM BEECHES. By Roger Fenton. 
 
 KENILWORTH CASTLE. By Philip DelaMotte. 
 
 Part IV. 
 
 ELM TREE IN UMBERSLEY PARK. By Alfred Rosling. 
 PENSHURST CASTLE. By Philip DelaMotte. 
 
 THE RUINED FARM. By Hugh Owen. 
 
 THE VILLAGE ELM. By Joseph Cundall. 
 
 *** Photographers desirous of contributing to this work arb 
 requested to address a letter to the Publisher. 
 
 LONDON: 
 
 JOSEPH CUNDALL, 168 NEW BOND STREET. 
 

 
 * 
 
 ♦