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

From: Eric Neilsen ^lt;e.neilsen@worldnet.att.net>
Date: 08/09/05-12:07:49 PM Z
Message-id: <20050809180756.E8AA9165ED08@spamf3.usask.ca>

Correct

Eric Neilsen Photography
4101 Commerce Street, Suite 9
Dallas, TX 75226
214-827-8301
http://ericneilsenphotography.com
> -----Original Message-----
> From: Sandy King [mailto:sanking@clemson.edu]
> Sent: Tuesday, August 09, 2005 10:50 AM
> To: alt-photo-process-l@sask.usask.ca
> Subject: RE: Pt./Pd. question acid pre-soak
>
> Eric,
>
> I am not clear what you mean. Are you saying that you used the oxalic
> acid pre-soak and did not see any increase in Dmax with the papers
> that you use?
>
> Sandy
>
>
>
>
>
> >
> >I ran test when this was talked about years ago and found little to
> support
> >it. I did not run test on a large sample of papers. I also queried those
> >that made the claim to see if they could also just add some oxalic acid
> to
> >their ferric and achieve the same increase in dmax. I got no response.
> >
> >Or is it simply a pH issue? Years ago Martin Axxon had suggested to me
> that
> >he felt a lower pH paper gave a better print with PT solution.
> >
> >
> >
> >Eric Neilsen Photography
> >4101 Commerce Street
> >Suite 9
> >Dallas, TX 75226
> >http://e.neilsen.home.att.net
> >http://ericneilsenphotography.com
> >
> >> -----Original Message-----
> >> From: Ryuji Suzuki [mailto:rs@silvergrain.org]
> >> Sent: Monday, August 08, 2005 9:59 PM
> >> To: alt-photo-process-l@sask.usask.ca
> >> Subject: 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 Tue Aug 9 12:08:12 2005

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