3166. To Recover Silver from Photographic Waste

3166.    To Recover Silver from Photographic Waste. To obtain the silver from a photographic bath, or from the rejected photographs and clippings, is a most important measure of economy in the art. The bath should bo filtered, and a solution of common salt added; this precipitates chloride of silver, which is to be collected on a filter, dried, and washed; then the metallic silver may be obtained from it by the action of metallic zinc, a strip of which being placed in the pulpy mass, will combine with the chloride, and leave the silver in a spongy mass of a gray color; after washing, this may be dissolved in nitric acid and crystallized. Another process is to mix the chloride with nitrate of potassa and fuse in a crucible - the silver is thus obtained in a button. The papers must be incinerated, the ashes collected and treated with nitric acid and heat; diluted with water, and filtered; it is now an impure solution of silver, to be treated in the same way as the bath. (See No. 3158 (To Recover Gold and Silver from Photographic Solutions).)

3167. To Clean off Collodion Pictures

3167.      To Clean off Collodion Pictures. A tuft of cotton dipped in methylic alcohol, and rubbed over the surface of the picture, will remove it entirely, whether varnished or not.

3168. Paper for Photography

3168.    Paper for Photography. The paper used for photography may be the finest satin post paper, of uniform texture, free from the maker's mark, specks, and all imperfections. The papers must be prepared by candle-light, and kept in the dark till used.

3169. Simple Nitrated Paper

3169.     Simple Nitrated Paper. This is merely paper brushed over with a strong solution of nitrate of silver. In brushing over the paper it must not be crossed. Its sensitiveness is increased by using spirits of wine instead of water. This paper only requires washing in water to fix the drawing.

3170. Muriated Paper

3170.    Muriated Paper. The paper is first soaked in solution of common salt, pressed with a linen cloth or blotting-paper, and dried. It is then brushed over on one side (which should be marked near the edge) with the solution of nitrate of silver, and dried at the fire. The stronger the solution, the more sensitive the paper. If the barytic solution (see No. 3181 (Barytic Photographic Solution)) be used instead of common salt, richer shades of color are obtained. A solution of 10 grains sal ammoniac in 1 ounce water gives a very sensitive paper. A due proportion must be observed in the silver and salt solutions, as follows:

Sensitive paper for the camera, use 50 grains common salt to 1 ounce water; and 120 grains nitrate of silver to 1 ounce water. Or: 60 grains of the nitrate with 40 grains muriate of ammonia, and 4 ounces water. Or: 100 grains nitrate with the barytic solution. (See No. 3181 (Barytic Photographic Solution).)

Less sensitive, for copying engravings, botanical and entomological specimens, etc.. The salt solution to contain 25 grains salt to 1 ounce water. The silver solution 90 grains in 1 ounce water.

For copying lace-work, feathers, patterns, etc.. The salt solution, 20 grains; the silver solution, 40 grains to 1 ounce. To fix the drawing on these papers, they must be first washed in lukewarm water, then dipped twice in solution of hyposulphite of soda (1 ounce to 1 pint), then in pure water, and dried.