Physical Ripening of Photographic Emulsions with Hardened Gelatin

Paper presented at a symposium on “Photographic Gelatin” organized by the Science Committee of the Royal Photographic Society, 1-4 September, 1970 in Cambridge.

Abstract

The paper presents information about the conditions in which the hardeners formaldehyde and chromic acetate can effect the kinetics of the physical ripening of “neutral” and ammoniacal silver bromide emulsions obtained at various excesses of potassium bromide. When a gelatin is partially hardened, there is no effect on the physical ripening of fine-grained emulsions. The crystal growth is restrained as a consequence of the hardening only when the emulsion grains are larger. In this case it is assumed that on the grain surface are formed thicker or more compact adsorption layers of gelatin, which reduce the rate of the diffusion processes and, hence, the rate of crystal growth. Chromic acetate exerts very strong restraining action on ammoniacal emulsions. This effect is explained not by the hardening of gelatin, but by the formation of chromic ammonia complex ions, which block the active centres of crystal growth on grain surface.

Notes

Paper presented at a symposium on “Photographic Gelatin” organized by the Science Committee of the Royal Photographic Society, 1-4 September, 1970 in Cambridge.