Re: Black spots in Pt./Pd.

From: Sandy King <sanking@clemson.edu>
Subject: Re: Black spots in Pt./Pd.
Date: Tue, 09 Aug 2005 12:45:04 -0400

> So what causes this, and is there any way to avoid it. I have a
> hundred sheets of this Lenox that I planned to use for palladium
> printing and hate to think that it will be no good. The last batch of
> Lexon I had printed beautifully.

If you suspect acidity and/or iron impurity is the culprit, and if you
don't care about identifying which of them is involved, and if your
process is compatible with small amount of citric acid residue, I
would soak the paper in warm, dilute citric acid solution for several
minutes and dry. (If desired, rinse the soaked paper before drying.)

Another possibility is contamination of reducing agent in
paper. Practically all fine art papers I tried contain some small
amount of reducing agent, possibly sulfite, some reducing
carbohydrates or related compounds used in paper production. This is
probably insignificant for all processes other than developed-out
silver gelatin process, but I'm naming it because I know it is there.
If you suspect this is in action, I would soak the paper in dilute
persulfate solution, peroxide solution, etc. and dry before coating
the sensitizer.
Received on Tue Aug 9 11:03:48 2005