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The photographic news
- Bandzählung
- 29.1885
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- 1885
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- Bandzählung
- No. 1380, February 13, 1885
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The photographic news
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Band 29.1885
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- Register Index III
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FEBRUARY 13, 1885.J 'The PHOTOGRAPHIC news. 103 works of Dr. Eder and Pizzighelli, Die Photographic mit Chlor- s'Mer Gelatine and Der Neue Eiscnoxalat Entwichler. The in vestigations of Dr. Eder are so exhaustive, that there is almost no room in this direction for any new and original remarks. After the image is developed it must be washed in four or five changes of water, and for the elimination of the iron it is left in a ten per cent, solution of alum for fifteen minutes ; it is then washed again in four or five changes of water. Leaving the prints long in the washing water is not advisable. Next, as to toning. Any toning used for albumenised paper will answer. I tried, successfully :— Gold chloride I grain Sodium acetate 30 grains Water ... ... ... ... ... 8 ounces Chloride of lime A trace Care must be taken that no trace of iron (from the developer) is left in the paper, as gold is reduced by iron salts, and spots or general greyness may be the result. Personally, however, I prefer and strongly recommend toning and fixing in one bath. A.—Sodium hyposulphite ... 30 ounces Water 30 ounces B.—Gold chloride.. lograins Water 20 ounces To solution A add slowly, and well stirring, four ounces of B• The bath is then ready for use. It improves by keeping, and when necessary, is replenished by the addition of fresh hypo sulphite of soda and of gold solution B. The print is to be kept in this bath for ten minutes, when it will be both toned and fixed. This bath keeps well, and improves by keeping. Care must be taken to add fresh gold and fresh hypo after a certain number of prints have been passed through the bath. If separate toning is used, fixing is effected in the ordinary 20 per cent, of sodium hyposulphite. And here I must give warning that in the operation of print ing care must be taken against any contact of the paper with hyposulphite of soda. This substance accelerates the action of the developer, and is the cause of spots in consequence. After fixing, the print must be washed from every trace of the hypo sulphite of soda, like any ordinary albumenised paper print. An erroneous notion is entertained by some that it will not require so much washing as such. The washed print, when dried spontaneously, will have the appearance of an albumevized print; but there is a very easy way of producing a surface equalled only by the finest enamel process, and to do this, a glass plate is rubbed with talc (French chalk), and the wet print squeezeed to it; this, when dry, can be easily peeled off, with a surface like glass. If the glass is per fect, no failure can occur ; but sometimes it happens, as is well known to enamellers, that through the invisible holes in the glass the print is spoiled, from a refusal to detach from the glass. I found that if a finely-polished ebonite sheet is used instead of glass, and the wet print squeezeed to it, without any previous preparation, as soon as it is dry it will peel off with a surface very little inferior to that from glass, and failures in this case are not to be feared. Naturally, the enamelled print will lose some (not all) of its exquisite gloss when moistened again, and in order to preserve it, the mounting material must be pasted to it before it is dry and separated. Now comes the question of the permanency of these prints. Time only will conclusively answer this question ; but, knowing by experience that silver-developed images keep so well in nega tives or transparencies, wc have reason to suppose that these newly developed prints will also prove equally permanent. Before I conclude, I must express my belief that this paper will be the paper of the future, and that before long it will super sede albumenized paper, not only for dark winter days, but for all printing, at any time, because, producing equally fine results, it is so much quicker to print, and permits a greater range of colour to be obtained. I shall not be surprised if, instead of the slow and tedious operation of printing, we shall have a suitable printing machine, in which the exposure will be produced by the simple movement of a handle, regulating the speed according to the intensity of the light, and perhaps an equally mechanical deve lopment. Machines for such purposes have been already designed, but the paper was not in existence; now, therefore, the time has arrived when they may be forthcoming. EMULSION MAKING. Notes about a LECTURE, by f. MYOTT.* The lecturer disclaimed any pretence to originality, and said he came before the meeting to give his own experience of everyday routine. The formula, therefore, would show no very startling deviation from those already in use, but was simply the state ment of one he had adopted after experimenting among many. He cautioned all who would be “ emulsion makers ” that much patience and perseverance were necessary, for many failures would come to the most careful of workers; but for all that, there was a great fascination connected with plate making that would tempt one to continue pouring their pounds, shillings, and pence down the sink, and perhaps not a little spoilt “ bromide of silver.” In order to give a better idea of what constitutes the recog nized requirements of a good emulsion, the lecturer gave a brief history of the rise and progress of the gelatino-bromide process, reference being made to the experiments of Dr. Maddox, and the modifications of Bennet, Abney, and Eder, until the latest im provement—viz., the introduction of iodide of potassium—was recommended. This latter he had experimented with some what exhaustively, with the result that he was strongly in favour of its use, being confident that it contributed largely to the production of bright and sparkiing shadows in the resulting negative, and prevented the development of fog when boiling the emulsion ; and he now adhered to its use on all occasions. He had also given gelatine of various makes some amount of study, and in his hands the use of equal portions of hard and soft sam ples, so often recommended, had proved unsuitable, and he now invariably adopted one part of hard to three of soft gelatine. The following is the formula used by him for a five-ounce propor tion : No. 1.—Bromide of potass 45 grains Nelson’s gelatine, No. 1 ... 15 „ Distilled water ... 1 ounce No. 2.—Silver nit. ... 60 grains Distilled water ... ... ... 1 drachm No. 3.—Iodide potass I grain Distilled water 1 drachm No. 4.—Nelson’s gelatine No. 1 ... 60 grains Swiss hard „ ... ... 20 „ Distilled water 1 ounce This would allow for an excess of bromide in the resulting emulsion, and would be found useful in keeping it free from fog during manufacture, and distilled water should be used to pre vent a precipitate of the carbonates or other matter forming. He preferred bromide of potassium to the bromide of ammonium, because the latter was more liable to change and get acid by keeping, and it was very necessary to use it while fresh. If it were not for this drawback, he would be inclined to favour the bromide of ammonium, as this was capable of giving an exceed ingly rapid emulsion. The bromide of potassium solution No. 1 should be slightly acidified if found alkaline on testing with litmus paper, and dilute hydrochloric acid should be used for this purpose. To form the emulsion, after allowing the solutions containing gelatine to soak some little time, Nos. 1 and 2 should be heated until the temperature was raised to about 150°. He thought that the temperature at which these solutions were when brought in contact was of some importance. The silver solution No 2 should be mixed with No. 1 gradually (say at about five or six times), shaking well between each addition. He some times used a small spray-producer for finely-dividing the silver ; No. 3 was then added. Now place the emulsion in a stone bottle loosely corked, and boil for an hour, now and then re moving the bottle and well shaking, after which allow to cool to 100° Fah., and after No. 4 has been warmed to a similar tempera ture, add to the emulsion. The temperature at which this operation was performed was also important. If the bulk of the gelatine were added when the temperature was high, the result ing emulsion would give a smooth and horny surface. The medium temperature would give a matt surface, and this was by far the best quality. Now pour out into a flat dish and allow to set; force through coarse canvas into clean water. After re peating this operation three or four times, it may be considered sufficiently washed. Now dissolve by gentle heat, and add three drs. of absolute • Delivered before the Halifax Photographic Society.
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