ISO 18917:1999

Photography — Determination of residual thiosulfate and other related chemicals in processed photographic materials — Methods using iodine-amylose, methylene blue and silver sulfide

Scope

1.1 This International Standard specifies test methods for the determination of residual thiosulfate and other
related chemicals in processed photographic materials.
1.2 This International Standard applies to silver halide/gelatin products that have been processed with a final
thiosulfate fixing bath and a water wash. This International Standard does not apply to stabilised black-and-white
products, thermally processed films, or instant-type products. The procedures given in this International Standard
measure residual thiosulfate, and the silver densitometric method measures residual related polythionate materials
as well. Measurements carried out by the procedures in this International Standard may, within the limitations stated
in annexes A and B, correlate with the image stabilities of processed photographs.
1.3 Film or plates with photographic-sensitive layers on both sides, or with a photographic sensitive layer on one
side and a gelatin backing layer on the reverse side, may contain approximately twice as much thiosulfate after
processing as samples having a coating on one side only. This situation will be true for materials for which residual
thiosulfate is determined by the iodine-amylose or methylene blue procedures.
NOTE For the method of reporting such results, see figure 1, example 2.
1.4 The iodine-amylose can be used with fibre-based paper, resin-coated paper, films and plates. It is the method
to be used with films and papers containing incorporated developing agents.
1.5 The methylene blue method can be used with fibre-based paper, resin-coated paper, films and plates but not
with films and paper containing incorporated developing agents.
1.6 The silver sulfide densitometric method measures thiosulfates, polythionates and all other residual chemicals
in a processed product that react with silver ion to form a silver "stain" under the conditions of the test.
1.7 A tabulated summary of methods, scope, etc. is given in annex B.