Platinum printers: dark stains on prints?

[Natha Congdon]

I realize there are alt process forums for Pt/Pd questions, but have found the t urnaround a bit slow, and there do seem to be some Alt process types lurking aro und here, so, without further apology:

I developed, cleared and washed a 12X20 Pt/Pd print using my usual technique (K Oxalate developer at 100 F, three 5 minute washes with phosphoric acid, 3 liters in each, the last wash 100% freshly made up solution, followed by a 20-30 min w ash.) The print has dirty gray stains, looking sort of like somebody walked ove r the print with dirty shoes. They're most visible along the white edge of the paper (It's Platinotype, by the way), but also in a few sections of the lighter sky. Only some areas are affected. The print otherwise looks fine. Couldn't f ind this described in the Arentz or Sullivan/Weese books. Any thoughts? I'd li ke to avoid another expensive mistake!

Thanks as always, Nathan

[Jim Galli]

Did you use a different cutter to cut the paper to size than you've used before? New roller wheel? Something else that is allowing microscopic steel residue to be left behind?

[Carl Weese]

Nathan,

Did you notice any "bleeding" from the black borders of the print during development? When there's too much of this the particles can deposit in the print or the border as stain--a sort of mechanical fog. Stains that are grey are either some sort of fog or unwanted deposit of partially cleared metal. Yellow or orange stains would be from lack of adequate clearing.

[Jorge Gasteazoro]

The culprit might be your phosphoric acid, maybe is exhausted already and not clearing your prints totally, get some litmus paper and check it's pH...anything above 4 or 5 and you are probably using an exhausted clearing agent.

Good luck.

[Natha Congdon]

Looking over the print, I think Carl is probably right, though I'm not clear why I am getting this bleeding now. As mentioned above, the last phosphoric bath is 100% freshly made solution 3 L, so I don't think the clearing is inadequate.

Thanks for your thoughts!

Nathan

[Joe Lipka]

Now that you have the problem solved, I note that you are using the Oxalate acid route to processing. I realize this is the traditional process, but have you considered going with more modern (and less dangerous) materials?