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The photographic news
- Bandzählung
- 6.1862
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- 1862
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 188, April 11, 1862
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Zeitschrift
The photographic news
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Band 6.1862
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- Register Index 619
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Band 6.1862
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April 11, 1862.] THE PHOTOGRAPHIC NEWS. 175 entirely, it little by little removes, in some measure, the parts feebly impressed, because, fixed upon the external surface, they rest upon a basis which has retained its solu bility.” THE TANNIN PROCESS — TRANSPARENCIES — IN STANTANEOUS PHOTOGRAPHY. BY WILLIAM ENGLAND.® As it is most desirable that everything coming under the obser vation or practice of the photographer tending to the advance ment and development of the art should be made known, I venture to occupy your time with a few remarks. An additional inducement to me to ask your attention, is the interest you manifested in the pictures which I had the honour of exhibiting before you at the last meeting of this society. It is to the method by which those pictures wore produced that I propose to call your attention. I do not pretend that I have much to say with which many gentlemen present are unacquainted, neither can I lay claim to much that is original, therefore it is chiefly to the details of manipulation I shall confine my observations. The process I adopt is that known as “ Major Russell’s Tannin Process.” I have tried many others, but have not been successful. Taupenot’s gives impressions too hard and strong in the lights, faults which the utmost care in developing has not overcome. The same, too, may be said of the Fothergill process, so far as my experience proves, besides the many diffi culties of manipulation ; such, for instance, as washing the plate too much or too little, and the unevenness of development, due no doubt, to the albumen coating being porous in some places and horny in others, causing the print when finished to present a very patchy appearance. I do not say that all those faults are to be placed to those processes. Probably by very long prac tice they may be overcome, and good results obtained; but I really believe that the simplicity of the tannin process places it at the head of all other methods, and that with it finer results may be obtained, not only as transparencies for the lantern or stereoscope, to whichit is so well adapted by the soft and beauti fully warm tones produced, but also in the production of negatives. Much has been said and written upon the long exposure required for tannin plates, and the great inconvenience of the film leaving the glass during development. In answer to the first objection, I may say that with a slight modification, to which I shall presently refer, and the choice of a suitable collo dion, I have been able to reduce the time of exposure to the average length given to wet collodion developed with pyrogallic acid; and I have no doubt that were it possible to prepare a solution of iron, or some other equally energetic developer, suit able for developing tannin plates, pictures might be produced absolutely instantaneously. As to the film leaving the plate, I at first found some difficulty, particularly with very new collo dion. I could not make up mind to albumenize or gelatinize my glasses, as recommended by some operators, previous to coating with collodion, not only on account of the time it occupies, but also the difficulty of getting a plate so prepared free from spots and dust. I can now, after considerable practice, prepare them in largo sizes, and then cut to steroscopic without injury to the delicate film, by which means a saving of time is effected. The collodion most suitable, so far as my experience enables >nc to speak, is prepared in the following manner :—To 5 parts of ether and 3 of alcohol, add sufficient pyroxyline to give a tolerably thick film. So soon as well settled, decant into another bottle, and measure off two portions of 10 drachms each : to one add 40 grains of bromide of cadmium, and to the other 30 grains of iodide of ammonium; shake till dissolved, and put by to settle. When thoroughly settled, add 1 drachm of each to 6 parts of plain collodion. I have tried various methods of iodizing, and prefer this mode to any other, not only on account of its being more freo from spots, but also that immediately after iodizing it is in as good a condition for working as the usual collodion after being iodized some days. During a great number of experiments in trying to increase the sensitiveness of dry plates, I found that the addition of honey had a remarkable accelerating effect, and by rendering the film less horny assists materially the development of the image. I am quite aware that the use of honey in photography is not now. We all remember the charming productions of Mr. Llewellyn and Mr. Maxwell Lyte ; but honey used simply or in combination with acid, as in the oxymel process, leaves the Plates tacky ami liable m injury from dust. This is not the Read at a meeting of the Photographic Society on Tuesday evening, April 1. case by using it in the proportions I shall presently recommend in combination with tannin. By following this method, and using collodion prepared as before-mentioned, the time of expo sure for stereoscopic pictures in a good light would average not more than from ten to fifteen seconds. After cleaning and coating the glass, sensitize in a 40-grain bath, and wash in a second bath of distilled water, to which has been added 30 or 40 drops of acetic ecid. The plate may remain in the latter while a second is being prepared. The plate is then thoroughly washed under a tap, and coated with the tannin solution composed of 15 grains of tannin and 15 grains of honey to the ounce of water. It is then ready to be placed in the box to dry. I may here remark on the groat care necessary to avoid stains. If possible, a silver dipper should be used, being more convenient to hold the plate in washing. When necessary to handle the plate, do so with a piece of blotting-paper ; also, in coating the plate with tannin, lay a piece between the plate and fingers. The drying box I find convenient has three shelves, and up one side is fixed a tin tube, under which a spirit-lamp may bo placed. After the necessary number of plates has been placed in the box, it should not be opened till they are perfectly dry, other wise a stain will appear across the plate where the action of drying has been checked by the admission of cold air to the box. Daguerreotypists will readily understand this from the difficul ties they may have experienced in drying off Daguerreotype plates, particularly the larger sizes. To prevent the film leaving the glass, an excellent plan is to pass a sable pencil, previously dipped in a solution of white wax and benzole, round the edge of the plate to the extent, say of one-eighth of an inch. This, for the purpose, is far superior to spirit varnish. The plates may then be stowed away ready for use, and, if properly prepared, will keep six months. On removal from the camera, place the plate in a bath pre pared with 10 grains of nitrate of silver and 5 drops of acetic acid to the ounce of water, allowing it to remain about one minute. By the adoption of this plan for dry plates, the action of the developer is almost as rapid as in the wet process. After wards develop with the usual 3-grain solution of pyrogallic acid. The development is so similar to wet collodion that I need not remark further than that no fear need be entertained of the film breaking up, the edges being kept perfectly dry and tight by the wax border. The second subject of my paper is the printing of transpa rencies. The mode of preparing the dry plates is much the same, except that for this purpose old collodion must be used. If of a dark red so much the better; otherwise in printing from a strong negative it is impossible to get an impression clean and well-defined, on account of the tendency of new collodion to solarize and present a weak and foggy impression : better tones will also be obtained by reducing the coating solution to 10 grains of tannin and 5 grains of honey to the ounce of water; the developer should likewise contain citric instead of acetic acid, as recommended by Major Russell; and unless a consider able amount of silver is added, the print is sure to be red or reddish brown, instead or purple. Pictures for the lantern should bo thin, very clean, and well defined; not developed so deeply as those for the stereoscope. I will conclude by making a few remarks upon instantaneous photography ; and here I may say that a very large amount of patience is necessary, and that failures are very plentiful—bad light, the absence of the sun at the identical moment the plate is most sensitive, the variations in the quality of the chemical agents employed, and, above all, the difficulties that attend the nitrate bath, which will sometimes unaccountably persist in giving foggy impressions. Again, we get beautifully clear plates, but with very little impression beyond the high lights. Now all this is very disagreeable ; but such is the case at present, and will continue to be, I fear, until we have a dry process suffi ciently sensitive. Where time of exposure is no object, of course we do not meet with these troubles. The collodion used in taking the negatives of the impres sions I have the honour of placing before you, was prepared in precisely the same way as before-mentioned, except that in iodizing, I use 3 grains of bromide of cadmium, and the same amount of iodide of ammonium, to each ounce of collodion. I am an advocate for the liberal use of bromides, having ex perienced their beneficial effects, particularly in photographing objects presenting violent contrasts of lights and shades. Under
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