Re: Black spots in Pt./Pd.

Actually, the issue of black spots and pre-soak are not related
issues. I just happened to have an operational problem with the
former, and a theoretical interest in the latter.

Sandy

>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 14:24:59 2005