GB188692A - A process for producing coloured photographs on paper or the like - Google Patents

Abstract

188,692. Lage, E. A. May 19, 1921. Colour photography.-In a process for producing colour prints on paper or the like, in which three colour-value negatives are successively copied on a single base which is re-sensitized for each successive image, the yellow partial image is produced as a chrome yellow image, the blue partial image is produced as an iron-blue image, and the red partial image is produced by a chromate process, the yellow image being maintained invisible until the blue and red partial images have been printed. A bichromate bath which is used to produce the yellow image is also utilized to sensitize the paper for printing the red image. An ordinary black gaslight or similar print is produced from the yellow negative, well rinsed, and bleached in a bath containing lead nitrate, potassium ferricyanide, and nitric acid. The print is washed, dried, and moistened with a solution containing ferric ammonium citrate and potassium ferricyanide. It is then printed fully under the blue negative, washed, dried quickly, and coated with a 3 per cent solution of potassium bichromate, which is allowed to dry. This develops the yellow partial image, but, owing to the yellow colour of the bichromate, maintains this image invisible, and also sensitizes the surface for printing from the red partial negative. The printing from this negative is continued until the image is just visible in the high lights; the print is then washed and dried and the red image is produced thereon by treatment with red pigment. The print is finally fixed in sodium hyposulphite, washed, and dried.