Eastman Kodak integral films

“Kodak Instant Print Film PR-10 was based on a dye release system that used ballasted preformed dyes and reversal emulsion instead of dye developers and negative emulsion. Processing started when the film passed between pressure rollers that ruptured the pod of reagent and spread the activator fluid within the package. The nonexposed silver halide grains were developed by a reversal mechanism. The process released mobile dyes that migrated to the image-receiving layer, where they were mordanted. Processing terminated when the pH of all layers was reduced to a level that did not allow further chemical reaction (Hanson 1976). PR-10 was later replaced by Kodak Instant Color Film, which had improved image stability under both dark and light keeping conditions (Tuite 1979).”

(Pénichon, Sylvie (2013): Twentieth Century Colour Photographs. The Complete Guide to Processes, Identification & Preservation. London, Los Angeles: Thames & Hudson, on p. 243.)