Polacolor Instant Photography
“Polacolor was commercialized in 1963 and became an immediate success. It was acclaimed as the “most outstanding single advance in photographic science made during this century” (Crawley 1963). Indeed, Polacolor introduced important new photographic concepts that involved some ingenious and complex chemical reactions. Each film unit consisted of a negative, a positive sheet, and a pod containing a viscous fluid reagent. In the negative, yellow, magenta, and cyan dye developers were coated in separate layers beneath the blue-, green-, and red-sensitized silver halide emulsion layers, respectively. After exposure in the camera, the two sheets were pressed together through a pair of rollers, the pod was ruptured, and the reagent spread between the two parts of the film, initiating development. During processing, the dye developers were oxidized by exposed silver halide in each emulsion layer. The oxidized dye developers were immobilized in proportion to the degree of exposure and development of the silver halide, while the unreacted dye developers were free to diffuse through the layers of the negative onto the image-receiving layer, where they were mordanted (Mervis and Walworth 2007: 284). After sixty seconds, the two sheets were stripped apart and the negative was discarded. Even after separation of the sheets, chemical reactions continued in the positive. A polymeric acid layer beneath the image-receiving layer helped stop all reactions by slowly diffusing its contents and reducing the pH of the image layer. In contact with the air, the surface of the print dried rapidly and the gelatin hardened, forming a hard, shiny surface resistant to fingerprints. To remedy the prints’ tendency to curl on drying, self-adhesive cardboard mounting cards the same size as the photographs were provided with each pack of film.”
(Pénichon, Sylvie (2013): Twentieth Century Colour Photographs. The Complete Guide to Processes, Identification & Preservation. London, Los Angeles: Thames & Hudson, on p. 234.)
Pénichon, Sylvie (2013): Twentieth Century Colour Photographs. The Complete Guide to Processes, Identification & Preservation. London, Los Angeles: Thames & Hudson, on pp. 234–236, on pp. 252–254 , on p. 258 and on pp. 264–265.