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 09:50:02 2005