Measurements of the Restrainer Content of Gelatin by a Photographic Means

Paper to be presentcJ at a symposium on “Photographic Gelatin” being orgnaniced by the Science Committee of The Royal Phologruphic Society on 19-22 September 1967 in Cambridge.

Abstract

An emulsion is prepared and chemically sensitized using the test gelatin and a suitable standard addition of thiosulphate sensitizer. The time and temperature of digestion are also controlled and the emulsion adjusted to optimum speed by varying the addition of a synthetic restrainer. The amount of synthetic restrainer required at optimum is an inverse measure of the restraining power of the gelatin and, if it is assumed that those gelatins which require the largest omount of added restrainer contain no natural restrainer, then by comparing the amount required by a test gelatin with this amount, the restraining power of the test gelatin is obtained in terms of the added restralner. Active gelatins had restraining powers broadly in line with their nucleic acid contents. Inert gelatins also showed considerable differences in restraining power but, as they contain negligible nucleic acid, these gelatins must contain other types of restrainer. The sensitometric properties at optimum are closely similar for most gelatins, even for some widely different gelatins, as the optimum, with each test gelatin, is reached under similar restrainer- sensitizer environment. Some gelatins differ from the majority and this is taken to indicate the presence of substances other than restrainers and sensitizers.

Notes

Paper to be presentcJ at a symposium on “Photographic Gelatin” being orgnaniced by the Science Committee of The Royal Phologruphic Society on 19-22 September 1967 in Cambridge.