Selenium Staining: Something I've found that might help others

I regularly (multiple 100s of prints) go from 2nd fix bath to Selenium with zero issues - but during my last printing session I noticed something interesting.

I had just mixed up a new 2nd fix bath and took note of the fact that the rapid fix concentrate was of questionable quality and possibly laden with sulfur - not quite rotten eggs, but it had a smell and characteristic yellow color. The 5L rapid fix concentrate was obviously not doing too well with 3L of airspace in the container.

Still, it was capable of fixing, so I carried on with 2nd bath -> rinse -> Se 1+20. Right after fixing and rinsing the prints were fine, but the second they hit selenium they stained yellow along the edges. Additionally they had a slight translucent quality (this is strange and I've never been able to explain it but it's similar to the look of paper in mineral oil). I finished with toning and washed as normal, but no luck, they had been artificially aged even after a full wash.

So it seems that while fixer->selenium is still fine one should really make sure their fixer is clean and not of questionable quality. The interesting thing is that had I just washed and bypassed toning I probably wouldn't have noticed an issue. The prints had already been fixed out in the 1st bath without issue - it's the residual sulfur from the second bad bath that caused the issue - but only in Selenium.

Once the thiosulphate has begun to decompose depositing sulphur the fixer isn't going to safely remove all the intermediary silver-thiosulphate complexes formed during fixing.

If you'd left the prints untoned you'd probably have had a slight grey veiling appear over time with exposure to light instead.

Ian

Prints were fixed in a 1st bath already - I doubt they'll have issues. Point being here in that just the presence of this degraded fixer along with selenium toner created an adverse climate for the print. In the past others have mentioned they had staining when going from fixer to selenium. What I'm bringing up here is that their fixer might have actually been significantly degraded (not beyond capacity, but decomposed).

One of Kodak's recommended tests for residual silver in papers is to use KRST at 1+9, usually you test a white rebate with a drop or two - a yellow stain indicates there's still residual silver. The test is in many Kodak publications.

Ian

Ian's explanation seems right on the money to me.

I think you had fixer with reduced fixing capability and, even though your prints had been through bath 1, ended up with incompletely fixed prints, tuning them yellow. The toner simply acted as a residual silver test, but for the entire print. On the up-side, it's nice to know that you have a built-in residual silver test in your work flow.

I doubt that the selenium was reacting with any by-product from the degrading of the fix, but rather with the residual silver in the prints in the form of insoluble thiosulfate compounds that the weakened fixer could not convert to simpler, soluble compounds.

Next time that happens, you know what to do: just mix up some fresh fix.

Best,

Doremus Scudder
www.DoremusScudder

I have some of the untoned test scraps sitting dry in the sink and can easily test for residual and film clearing of the 1st bath when I get home, however the 1st fix bath had just been rotated from a previous 2nd - which had maybe seen 2nd fixation of around 100 5x7s or so. It's completely possible that it was on it's way out but very unlikely being a 2nd fix bath and not getting hit too hard with exhaustion.

More importantly though, during printing I had toned a few prints that had only seen the 1st bath (to gauge exposure) and they received zero yellowing or other issues. What I'm saying is that any print that went into that second bath experienced yellow staining upon contact with selenium. The prints that went from 1st bath to selenium (only a couple) had no issues. I do my 2nd fixing at the end.