Quote Originally Posted by Gerald C Koch View Post
It is not only the buildup of silver in the fixer that is of concern but also halide ions such as chloride, bromide and iodide. Iodide is a particular problem since it causes the fixing bath to exhaust more rapidly.
Hi Gerald, I don't believe that the halide concentrations will behave differently than silver, since they are all results of the same mechanism. So as long as the silver content is in an "accpetable range," as per the manufacturer, so should the halides also be.

The spreadsheet-modeling that I just did, for build-up of stop bath in the fixers should also be valid for contaminants in the stop bath, such as developer residue. What I'm finding is this: if you can successfully run 4 cycles, you ought to be able to run 10 or more. In my model (depending on parameters, tank size and carry-over rate), whatever stop bath concentration exists in either fix bath on the 4th cycle, has only increased on the order about one percent (or less) by the 10th cycle.

ps: in my earlier example, modeling capacity differences between 1-stage and 2-stage fixing, my approximations were based on paper, not film. Film might typically have 5 or 10 times higher silver-loading than paper, so the ratios might shift around. I don't really know, since I didn't try it.