GB360109A - Color photography - Google Patents

Abstract

360,109. Colour photography. DEHN, F. B., 103, Kingsway, London.- (Du Pont Vitacolor Corporation, M. B. ; 207, North Occidental Boulevard, Los Angeles, U.S.A.) Sept. 8, 1930, No. 26806. Drawings to Specification. [Class 98 (ii).] In a process for producing colour transparencies, complementary colour record negatives are taken of the object and a positive is prepared from one of them, this positive and the other negative being then printed in different strata of a single emulsion. A light obstructing dye such as tartrazine is added to the emulsion to prevent printing through. The images are developed together and the outer one is bleached with a bleacher which tans the gelatine in contact with the silver image. The image in the inner layer is then dye-toned or chemically toned and the unhardened gelatine of the outer layer died in a complementary colour. The bleaching bath may comprise potassium ferricyanide, potassium bromide, potassium bichromate, acetic acid, and potassium alum. The inner image may be bleached in a bath' consisting of oxalic acid, vanadium oxalate, and potassium ferricyanide and dyed with chrysoidine and fuchsine or of uranium nitrate, potassium oxalate, and hydrochloric acid, or may be toned with potassium oxalate, ferric nitrate, potassium ferricyanide, and hydrochloric acid. Pinatype red D and Wool green S may also be used as dyes. Specifications 130,603, 160,137, and 193,069, [all in Class 98 (ii), Photographic processes &c.], are referred to.