GB402599A - Process for producing pure whites and a pure yellow in multicolour screened photographic pictures - Google Patents

Abstract

402,599. Colour photography. DURKOPPWERKE AKT.-GES., 2, Nikolaus D³rkopp Strasse, Bielefeld, Germany. Dec. 12, 1932, No. 35188. Convention date, Dec. 10, 1931. [Class 98 (ii).] In order to obtain pure whites and a pure yellow in printing from a coloured negative on to multicolour-screen panchromatic sensitive material, the screen lines of this material are formed of colours which may subsequently be partially bleached, the red and green both bleaching to yellow, and the blue partially bleaching to a lighter blue. The print is developed in a tanning developer, then treated in a tanning bath which slightly bleaches the developed silver and strongly hardens the gelatin according to its silver content, and is finally placed in a bath containing potassium metabisulphite, spirit, ammonia and sodium thiosulphate which removes the unexposed silver halide and partially bleaches the screen lines in the above-stated manner at the non- hardened portions of the gelatin. The slight spreading of the hardening action of the developing and tanning baths from the silvercontaining gelatin lines to adjacent unexposed lines is relied upon to yield the true colours of the picture when the screen lines are partially bleached. In an example, the green lines are formed of a mixture of pyrazol yellow and acid green, the red lines of a mixture of pyrazol yellow and acid rhodamine, and the blue lines of a mixture of patent blue and acid violet, the acid green and acid rhodamine being bleached out, and the patent blue and acid violet being partially bleached, from the unhardened gelatin in the final bath.