Quote Originally Posted by Rudeofus View Post
Note that neither Haist, nor probably the other authors were at liberty to disclose trade secrets, and alkaline fixers were once considered trade secrets. Haist does describe how F-6 improved on F-5 by raising pH just a notch to make archival washing possible while maintainung low pH for proper hardening. When Anchell and Troop write about alkaline fixers, you can assume they did the tests to make these claims, remember where the 'T' in Formulary's TF-4 and TF-5 comes from
Regarding F-5/F-6, again, these are hardening Na Thiosulfate fixers. The type of hardener also makes a difference. Still, the discussion in Haist regarding fixer pH and washing (spread throughout the fixation and washing chapters) seems inconclusive. There are parts indicating the washing of gelatin is improved as fixer pH is raised to the isoelectric point (still acid), increasing fixer pH far above the isoelectric point of gelatin may actually retard gelatin washing, the rate of gelatin washing was not materially different for a chrome alum hardening fixer pH 3 and F-24, etc. Then there's the paper base with FB papers - the rate of paper washing is the same within a fixation pH range, the rate of paper washing is not materially affected by fixer pH, the rate of paper washing is improved with swelling when an alkaline bath is used after fixation, etc.

Regarding Anchell/Troop, I would not assume anything actually. Absolutely no evidence is presented to support any of the voluminous conclusions the authors make regarding a myriad of materials and chemicals. There are also plenty of incorrect statements, and conclusions I don't agree with. Sorry but I can't take everything Troop says at face value, and there are clear biases in those books.

Until I see credible test data, I remain unconvinced of the benefits (besides no bleaching) of alkaline Ammonium Thiosulfate fixers vs otherwise similar acidic fixers from Ilford or Kodak. There are also potential issues with alkaline fixers related to how development is stopped.