Re: Pt./Pd. question acid pre-soak

I don't do platinum/palladium printing so I can't answer the question,
but if anyone is to do the test, I suggest for the comparison part to
use unbuffered mineral acid in a controlled amount to maintain the
target pH, if you want the results to be interpretable. Oxalic acid is
a dicarboxylic acid, which can be involved in reactions with metal
ions. In particular, oxalic acid makes a soluble compound with ferric
ion. Citric acid is more active in similar reactions with a wider
range of metals, and it's not a good comparison target for this
purpose. Citric acid having more carboxyl groups as well as having one
carboxyl group attached to the same carbon as the hydroxyl group makes
it very reactive with metal ions. Though not ideal, acetic acid is ok
for the comparison in spite of its carboxyl group.

From: Sandy King <sanking@clemson.edu>
Subject: Pt./Pd. question acid pre-soak
Date: Mon, 08 Aug 2005 20:37:03 -0400

> As we know a pre-soak in a 1-2% solution of oxalic acid can add quite
> a bit of Dmax in Pt./Pd. printing with some papers. Does anyone know
> the mechanism of how this works? Is it merely a question of
> acidifying the paper? Has anyone ever compared the results between
> papers pre-soaked in oxalic acid and in some other dilute acid
> solution, say a 1-2% solution of citric acid?
>
>
>
>
> Sandy
>
Received on Mon Aug 8 20:58:46 2005