Knight's Mechanical Encyclopedia, P., Pho′to-gel′a-tine Pro′cess.

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Pho′to-gel′a-tine Pro′cess.

One in which gelatine, prepared chemically, usually by the bichromate of potash, is made to receive a photographic image, which may become a printing-surface or be transferred to a stone or zinc to form a printingsurface thereon.

The term may be used to distinguish those processes employing gelatine, from these in which starch, gum, asphaltum, etc., are used.

The processes are various. For early items on this subject, see gelatine process. See also Albertype; Heliotype.

Gelatine Processes. a. The drawing or print being in lines or dots, a negative on glass is obtained. From this a print on a film of bichromated gelatine is obtained, and this, after suitable treatment, is transferred to stone and rolled up for printing. Osborne's process. See photolithography.

b. A photographic positive on glass is placed over a sheet of talc bearing a film of bichromatized gelatine. This being exposed to the light, through the talc, the gelatine is hardened, according to the intensity of the transmitted light, leaving unaltered the parts in perfect shadow. The film being washed in hot water, the unaltered gelatine is dissolved away, leaving an intaglio plate in gelatine, in which the depressions correspond to the light portions of the picture. A cast forming a cameo in metal is obtained by electro-deposition or by a press, giving a printing-surface in relief. A peculiar ink is used, consisting of gelatine holding coloring matter, the degree of depression determining the quantity of ink and consequent depth of tone. The Woodbury process (which see).

1877.

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Knight's Mechanical Encyclopedia
Knight, Ed.

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Pho′to-gel′a-tine Pro′cess.

Knight's Mechanical Encyclopedia Knight, Ed.

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Pho′to-gel′a-tine Pro′cess.

Knight's Mechanical Encyclopedia
Knight, Ed.