About stop bath (to Pete and others):(posted 8275 days ago)The major reason I use water rinse is really a passive one; I don't want to mix a stop bath unless I have to. If there is any benefit of water rinse over stop bath, it is a bit of what's claimed for water-bath development, and of course less stress to gelatine (how much less, important or not, etc., are different matter, though). That is, if I have to minimize water usage or if the developer is stain-prone, I will use stop bath.
If I want a safe and effective stop bath, I would buffer the pH about 5.5 and reuse it until it dies. Even with small concentration, pH of the fresh acetic acid bath can be far lower than I want. If I have only a tiny (much less than you suggested) acid, even if the pH is low the stop bath won't work. You know all these stuff. A textbook way is to throw in some acetate but straight boric acid works well also. (Citric acid is stronger than acetic acid)
With some exceptions, non-hardening fixers should work fine even if some film developer is carried over. Usually, sulfite is in fixers to prevent sulfrization but this also prevents possible staining. I wonder why people don't suggest to formulate highly buffered b&w fixer to omit stop bath altogether. Mildly buffered stop bath can last longer than fixers in terms of processing capacity, so there seems to be negligible chemical waste. Any idea?