This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...mixing 10 grammes of sulphuric acid with 100 grammes of water. After standing for some hours, the following test should be made: Coat a plate with collodion, sensitize it, and let it drain well; develop it in the ordinary manner, without exposing, and wash and fix the plate as usual. After fixing, if the glass is not ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...mixing 10 grammes of sulphuric acid with 100 grammes of water. After standing for some hours, the following test should be made: Coat a plate with collodion, sensitize it, and let it drain well; develop it in the ordinary manner, without exposing, and wash and fix the plate as usual. After fixing, if the glass is not perfectly clear, but is still covered with a thin, light deposit which may be removed by the finger, a few more drops of acid must be added, and the experiment repeated; too much acid must never be added at any one time, and care must be taken that the plates used in the experiments are perfectly clean. As the deposit upon the plate may likewise be caused by the action of light, all chemical rays must be carefully excluded from the dark-room.--Edward L. Wilson. Pure silver and distilled water will make a bath which will not require sunning or be as many gradations of tone as possible. If few half tones only are present in the negative, it is impossible to obtain a brilliant print from the same, as the result will either be weak or hard, according to the difference in the thickness of the film in the lights and shadows. 136. Let us suppose that a picture possesses twenty different gradations of tone; in order to be able to furnish a good print, the negative must then be composed of twenty different thicknesses of deposit, which are visible when the image is seen by transmitted light. A negative which begins with perfect transparency, presenting no hindrance whatever to the light in the production of the deepest tones, and which possesses the twenty gradations of tone, is capable of giving a perfectly brilliant result, although it may not appear very opaque in its highest lights. But if the deepest shadows are covered with a deposit equal to ten ...
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