in a press, and some special liquid gelatine ink is poured on to it, and a sheet'of non-absorbent paper placed over. The press is now closed, and pressure being applied, it is obvious that the ink will leave the high-lights and collect in the shadows. When the gelatine ink has set, the paper is removed, bearing the image, and is fixed in alum and dried.
Stannotype. This is also an invention of Mr. Woodbury, and in this process an image in intaglio is produced by exposure of a bichromated gelatine film under a positive, and this is coated with tinfoil, and used for printing from in almost the same manner as in Woodburytype.
Wood Spirit, or Wood Naphtha. This is a crude form ot methylic alcohol (see Alcohol, Methylic), and is used in the preparation of methylated spirit. The crude wood spirit is sometimes used instead of alcohol as a solvent in varnish making, and it usually contains about 10 per cent, of acetone.
Wothlytype. An old method of making prints on collodionised paper, the nitrate of silver and nitrate of uranium being combined in the collodion.
Yellow Fog. See Fog.
Yellowness of Prints. See Toning.
Yellow Stain. See Clearing Bath.
Zinc (Ger., Zi?ik ; Fr., Zinc; Ital., Zinco). Zn = 65. Exists as calamine or carbonate, as sulphide in zincblende, as oxide, and occasionally in a pure state. It is used in several photo-mechanical processes, and its salts, the bromide, iodide, and chloride, which are formed in somewhat similar manner to the cadmium salts, are not much used. Zinc hypochlorite has lately been recommended for making hypo eliminator.
Zincography. A photo-mechanical printing process, in which the image is impressed upon a zinc plate by means of a greasy ink, and an etching fluid being applied which eats away the groundwork, leaving the image in relief, so that it can be printed from like ordinary type,
Zoetrope (£aco, or C^t 1 am active, or live, and rponos, a style or fashion). The application of photography to the Zoetrope