The acid in acidic fixer is what makes selenium toner deteriorate. If you use alkaline fixer the print can go straight into the Kodak Rapid selenium toner, which as has been pointed out contains a lot of thiosulphate.
If one were to use a near-neutral fixer, like Kodak C-41 (pH around 6.5), does anyone know if that is acidic enough to precipitate KRST?
Whne Agfa Universal Fixer was available (pH around 7.5) I found that I could put a print directly into KRST after the second fixing bath. I haven't experimented with (expensive) KRST now that the only near neutral fixer I can get here is Kodak Flexicolor or the corresponding Fujifilm one.
I use TF4 and simply ignore all that HCA and double-tray fix headache. Prints are placed in a try of
plain water until the end of the work session when they are toned.
I'm not a photochemist, nor do I play one on TV, but I do know from the MSDS that KRST concentrate contains about 40-45% ammonium thiosulfate aka Rapid Fixer. Whether or not you do HCA before the toner, my view is that it should always be done after the toner to get rid of that thiosufate. The toner does work differently when the print comes straight out of the final fixing bath into it (and IMO works better as in more flexibility) but as someone alluded to earlier, a black precipitate forms in the toner sooner than would happen if the print was washed beforehand. I always assumed the precipitate was silver selenide but I don't know for sure. I always thought the precipitation occurred once the toner solution reached a low enough pH from the act of putting unwashed prints directly into the toner from the fix. Again I assume the toner pH changes depending on the foretreatment of the print.
I would suspect using HCA or another alkali during or before toning changes the toning solution pH (like I assume the added fixer might) and produces a different result.
Based on these assumptions I either do one of these procedures depending on the effect I'm after:
1) Tone the print directly out of the final fixer bath, then HCA and a final wash. This seems to give me better split-tone effects with certain papers at the expense of toner life.
2) After the final fixing bath, I rinse the prints briefly, HCA for 3-5 minutes, then they are fully washed for 30minutes. They are then toned and given a second HCA treatment and another 30 minute wash to remove the thiosulfate present in the toner formula. This takes longer and uses more water, but reduces possible staining or irregular toning and improves the shelf life of the toner. However, I usually prefer the first procedure.
Hey ho, here we go - been back in the darkroom again and reprinted the negs again using MGWT.
As normal prints were put into a holding water bath after fixing till the end of the printing session and then rinsed for about 5 mins in fresh water. Then popped into the selenium toner and hey presto - colour change at the rate/intensity that I would have expected. Then into HCA before final wash for 20 mins. Nice results and better than the first set!
Normally give a longer pre-tone wash and have to dry before toning another day, followed by another long wash, so less washing this way. I did have in my mind that excess fixer carry-over into the selenium would accelerate the forming of solid precipitate particles (which is perhaps where I got the idea of using HCA pre-selenium) and give patchy/inconsistent toning results.
Having a bit of a read around, patchy results are more likely due to insufficient fixing rather than insufficient pre-toning washing. Anyhoo, better finished results now and lessons learned - HCA after selinium toning!
Cheers for the inputs.
Also I've always been under the assumption that adding or carrying over HCA to Se toner will kill it's longevity.
All that really needs to be done is for the print to be fixed completely. This is where double fixing comes in so usefully. And since the print doesn't require a strong wash beforehand more water and time is saved.
Stop worrying about grain, resolution, sharpness, and everything else that doesn't have a damn thing to do with substance.
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Just a funny note: On my Labor Partner Selenium toner bottle it says:Use of furter watering aid is not required (http://www.macodirect.de/rollei-sele...on-pi-211.html)
So my question is, HCA and final wash after selenium toning is in all above posts said to be important, and all off you is doing it. What has gone wrong in the type writer to the "user manual guy" at Rollei?
Is there a possibility that it is a different formulation to Kodak Rapid Selenium Toner?
Originally Posted by DarkMagic
Or, Hypo Clearing agent helps to remove not only straight thiosulphate but also various compounds of thiosulphate and silver. Maybe by the time the print has been toned in selenium it has experienced an extra fix so there are no longer the silver complexes, just thiosulphate which might wash out in water relatively quickly. Just a guess!