GB770959A - Improvements in a photographic iron-silver color process - Google Patents

Abstract

770,959. Photographic iron-silver colour process. MARTINEZ, M. P. L. Aug. 13,1954 [Aug. 21, 1953), No. 23632/54. Class 98(2) A film is sensitized with a ferric salt, imagewise exposed to produce ferrous ions in the light-affected areas, treated with a silver salt solution to produce a silver image, and treated as by toning, dye toning, dye imbibition (mordantly), and particularly bleaching and colour development, to produce a colour image from the silver image. For multicolour images sensitizing and all other procedure is repeated using a set of separation negatives for the exposures. The ferric sensitizers require intense light exposure but such and all operations can be effected to a continuous moving film and have the advantage in multicolour work of resensitizing the film equally without regard to any existing images, to produce, finally, multicolour images in the form of a colour mixture all in one plane and without discernable grain. Three formulae for the ferric sensitizers, two of which contain gelatin, for processing with an ammoniated silver nitrate solution containing sodium sulphite and borax are provided; processing first yields a sepia to black image which is fixed and washed normally and is then ready for the colour procedure. In Example 1 a gelatin coated celluloid film is imersed for one minute in ferric ammonium oxalate solution, dried for another minute, strongly exposed for one to three seconds under the green filter negative of a separation set, immersed for 30 seconds in the silver solution quoted above, rinsed, fixed in hypo for one minute, washed for four minutes, bleached for one minute in a potassium ferricyanide - oxalate solution, washed, colour developed to magenta in an alkaline diethyl - p - phenylene diamine with p - nitro - benzyl cyanide solution, and then bleached again, rinsed, fixed and washed as in normal practice. Without drying the same ferric sensitizer is applied again and the whole sequence performed twice more using a phenyl phenol salt as cyan developer and acetoacetanilide for the blue. In Examples II and III a normal positive film is exposed under the green filter negative and colour developed to magenta in the normal way and the other two colours are provided by the ferric sensitizing sequences of Example 1.