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Abstract
Binder-free silver bromide suspensions were used to study the influence of definite amounts of gelatin on sensitometry, rate of development and rate of fixation. Development and fixation are strongly retarded by gelatin. The retardation increases linearly with the gelatin concentration until the surface of the silver halide is covered by a close- packed monolayer. Higher concentrations have little supplementary effect. Gelatin increases the selectivity of development and gives rise to filamentous silver. In this sense however it is not unique, as binding agents such as casein, polyvinylpyrrolidone or polyvinylalcohol behave qualitatively Identically. High-isoelectric-point gelatins cause higher retardation of development and fixation than normal-isoelectric-point gelatins. This phenomenon has been attributed to a stronger adsorption of the high-isoelectric-point gelatins. Gelatin impedes the regression of the latent image. A monolayer of gelatin is sufficient to prevent most of the fading. The excellent anti-fading property of gelatin has been ascribed to several causes: a strong adsorption to silver halide, its reducing power and the capacity to chelate metal ions. The amino acids, methionine, histidine or alanine are less effective presumably because they are only weakly adsorbed. Of the other compounds examined on its anti fading capacity only the proteins casein and lactalbumine as well as the bromine accebtor acetone semicarbazone gave results equivalent to those with gelatin.
Notes
Paper presented in part at a Symposium on “Photoraphic Gelatin” organized by the Science Committee of the Royal Photographic Society on 19-22 September 1967 in Cambridge.
Research sponsored by the “Instituut tot aanmoediging van the Wetenschappelijk Onderzoek in Nijverheid en Landbouw” of Belgium.