ABSTRACT
An incentive for using Kodak C-41 fixer for black and white is that in some areas it is the most economical fixer that can be bought. Kodak’s Ron Mowrey observes that thiourea and DTOD are also known to be superadditive both with thiosulfate and thiocyanate. Thiourea is probably best kept out of most darkrooms, because it fogs unexposed materials and, as Grant Haist has remarked, once it is in a darkroom, it is very hard to get out. Grant Haist spent much of his career investigating mercaptans as fixing and stabilizing chemicals. Scientists working on alternative fixing agents widely assumed that the compounds they were studying would create more stable silver images than thiosulfates. Potassium thiosulfate is less active compared to the ammonium or sodium salts. Thiosulfate is reported to be true even when tested with a film containing a large amount of iodide.
