3163. Preservation of Photographs

3163. Preservation of Photographs. H. Cooper, Jr., of England, gives the following formula for a preservative varnish which is stated to be an entire protection against fading: 1 drachm gum damar dissolved in 1 ounce benzole. 1 drachm paraffine, dissolved in 1 ounce benzole. Mix 4 parts of the paraffine solution with 1 part of the damar solution. Photographic prints covered with this varnish are impermeable to water. A solution of the parafiine only will do ; but it is better with the gum damar.

3164. Everlasting Photographs on Enamel

3164.     Everlasting Photographs on Enamel. First-class photographs, either negatives or positives, may be taken on Duchemin's enamel (see No. 2402 (Duchemin's Enamel for Labels, etc)) without collodion, by using bitumen, or citrate of iron, or perchloride of iron and tartaric acid, or bichromate, or any other salt. A* good solution for this purpose is, water, 100 parts by weight; gum, 4 parts; honey, 1 part; pulverized bichromate of potash, 3 parts Filter the liquid, spread it over the enamel, and let it rest, after which, expose it to the camera. Develop the image by brushing over it the following powder: Oxide of cobalt, 180 parts by weight; black oxide of iron, 90 parts; red lead, 100 parts; sand, 30 parts. Decompose the bichromate by immersion in a bath formed of water, 100 parts by weight; hydrochloric acid, 5 parts. "Wash it in clean water and dry it; and lastly, vitrefy the proof on a clean piece of cast iron, the surface of which has been previously chalked. One minute will suffice for indelibly fixing and glazing the photograph, which must be carefully and slowly allowed to cool. Photographs on enamel of any size, taken in this manner, are perfectly unalterable under all atmospheric conditions, and may consequently and aptly be called everlasting photographs.

3165. Searing's Process for Photographing on Wood for Engraving

3165.    Searing's Process for Photographing on Wood for Engraving. The block on which the picture is to be made is first dampened with water, then whitened with enamel rubbed from the surface of good enameled visiting cards. Rub gently, removing only the enamel, after which it is brushed smooth with a moderately stiff brush, from right to left and up and down, making a smooth, even, and very thin surface. Allow this to dry, after which it is flowed with a solution of albumen, made with the white of 1 egg and 16 ounces of water, dried by heat or allowed to dry spontaneously. Now coat it with another albumen solution made as follows: White of 1 egg; water, 4 ounces; chloride of ammonia, 40 grains. Beat the whole to a thick froth. Allow to subside, then decant or filter through a fine sponge placed in a glass funnel. Pour a sufficient quantity on one comer of the block to cover it, when spread around with the aid of a ^ or 1/6 glass.(using the edge). Allow the surplus solution to drain back into the bottle. Dry this by a gentle heat. Next flow on, in the dark room, solution No. 3, prepared as follows: Ether, 1 ounce; alcohol, 1 ounce; gun-cotton, 8 grains; nitrate of silver, 30 grains; dissolve in as small a quantity of water as possible, and allow to settle for a few days, protected from the light. Again dry the block by gentle heat. It is now ready for exposure under the negative. A porcelain printing-frame, or any other suitable method, may be used to print it. After printing, solution No. 3 is removed from the surface of the block by dissolving in ether and alcohol, assisted by rubbing gently with a soft sponge. The picture can now be toned and fixed in the ordinary way, or fixed and toned at one operation, by the hypo and gold bath. After being allowed to dry, it is ready for the engraver.