Hmm, that's interesting because I've seen TF-3 recommended as a fixer and its formulation is:
Ammonium thiosulfate (58-60%) 800ml
Sodium Sulfite (anhydrous) 60 g
Sodium Metaborate 5 g
Distilled water to make 1000 ml
60g/L seems like quite a bit, but maybe not?
I don't know if this is correct. The stain caused by pyrogallol, catechol, and hydroqionone consists of oxidation products (polyphenols) of the developing agent. These are lumped together under the term humic acids. The stain is dark colored and insoluble in water. I doubt whether the stain once formed can be bleached by the bisulfite ion in the fixer. The stain that forms in developer trays is the same substance and it is very difficult to remove requiring a strong bichromate bleach.
Originally Posted by Michael R 1974
Humic acids are not soluble in acid solutions but dissolve in strongly basic ones.
Perhaps some of the more chemically inclined can chime in here. The stain might be more or less vulnerable to sulfite after development depending on the type of developing agent, or perhaps after development a fair amount of sulfite (for example the amount in TF3) can be tolerated. But I've always read that a fixer like plain hypo (ie no preservative) is ideal for stained negatives, and that you definitely don't want to use a hypo clear at the washing stage since since a hypo clearing agent is basically all sodium sulfite with some bisulfite added to bring down the pH.
I have degrees in chemistry which is why I questioned the exposure to sulfite after development. From a purely chemical perspective the stain once formed is insoluble and hard to remove. It will only dissolve in concentrated solutions of sodium or potassium hydroxide. I doubt that sulfite ion is a strong enough reducing agent to bleach the stain.
Unfortunately there seems to be little scientific study of staining developers. What I have found on the internet is mostly conjecture and personal bias. There is also a lot of bad information and even mysticism. One example, the need to place the negatives back into an alkaline solution after fixing.
Perhaps an experiment is in order. I've never tried to get rid of the stain with sulfite after development so I can't say I've observed it first hand. My process when experimenting with staining developers was based mostly on what I read in Anchell/Troop combined with various articles and questions at workshops. Since I haven't tried to reduce the stain myself, I'll defer to your expertise for now.
What are some non-acidic commercial fixers?
If near neutral is good enough, Kodak Flexicolor fixer (made for some kind of colour processing but quite suitable for black and white film and paper) is often significantly cheaper than "black and white" fixers. Its pH is around 6.5, so not far from neutral.
I use it since the demise of Agfa FX-Universal which was sold as a fixer for colour and black and white. Its pH was around 7.5 (so it was truly alkaline, but not much).
Ilford Hypam fixer has a pH of about 5.5 and it works just fine with pyro stain.
Originally Posted by john_s
I actually once developed two sheets of 4x5 film in PMK (maybe it was the original Pyrocat) and put one into a water rinse instead of stop bath, and the other went into Kodak Indicator Stop Bath. They then were fixed together. The sheet through the water bath was about 0.01 density units higher than the one in the Indicator Stop Bath. I atribute the difference to just random error of the densitometer, or perhaps the water bathed film continued development for just a few second more than the stop bath film.
But I hope this shows that pH of the stop has little effect on the pyro stain.
I suspect that the pH of the fixer has little effect as well.
Hmm, so maybe my Ilford Rapid Fixer will work just fine? Does it get discarded after the fix, or poured back into the bottle?
Thanks for all the replies so far.
I suggest you test it for yourself. It's really the only way to know for sure since there are so many variables. As I said before, the conventional wisdom regarding staining developers (of course this is a generalization as there are many different formulas) is that to get maximum imagewise stain, it is best to keep the process alkaline or neutral from start to finish, and to keep sulfite low from start to finish. This would mean use a water stop instead of acid stop bath, and use a neutral or alkaline fixer with low sulfite (example TF3 with sulfite removed or TF4). Although Gerald presents valid arguments to the contrary, the chemistry of film processing always appears to be somewhat more complex than expected. It is also important to keep the words "maximum stain" in perspective. It's easy to come away from certain readings with the impression you will get hugely different amounts of stain depending on whether or not there is sulfite in your fixer, or whether or not you use an acid stop bath/fixer. The differences are likely much smaller than that, which would tend to support Gerald's reasoning.
The degree to which the after-development alkaline and low sulfite requirements are true is likely somewhat variable depending on the formulation, development technique and the film. The only way to know for sure is to try. The one piece of conventional Pyro wisdom I would say is least true is the recommendation to put the film back in the developer (ie alkaline environment) to increase stain. Everything I've ever read on the subject indicates all this will do if anything is increase general stain (ie fog), not imgewise stain.
Just to show different Pyro formulas work differently, one notable exception to the conventional rules is Wimberly's WD2H+. Wimberly is one of the founding fathers of modern Pyro developers. Regarding WD2H+ (a developer that produces an fairly strong orange-yellow stain), he makes a point of indicating this developer's stain is achieved entirely in the development stage, and is made permanent at that stage, so that there is absolutely no difference in the final negative whether you use an acid stop bath, and acid fixer, versus a neutral or alkaline after-development process.
Testing 510-Pyro and your film with different fixers would be relatively easy. Expose and develop two negatives identically, fix one in an alkaline fix (with sulfite), fix the second negative in Ilford Rapid Fix. Bleach away the silver and see if one negative has more stain. If you see no difference you could then do a sulfite test. Try giving one of the negatives a standard hypo clearing agent treatment and see if there is a loss of stain.