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

Eric,

Exactly. I was trying to figure out if anyone had done any tests
matching the acid in the developer to the acid of the pre-soak.

Some of the papers I use don't like the pre-soak, Stonhenge being one
of them, The acid pre-soak simply removes the coating of this paper
so when you print with it it absorbs a huge amount of sensitizer, and
the resulting prints have very granular look.

Sandy

>Sandy, that makes more sense. So the testing that was done with the 1% to
>2% oxalic acid treatment was to soak it in a bath or was it coated on and
>let dry? (I coated on a 2% solution for my test.)If I were looking to
>counter act a reaction, I'd look to an equivalent. So if for instance I was
>coating a 16x20 piece of paper with a 2% solution, I could quantify the
>amount of oxalic acid in total grams used. This would be quite difficult if
>I soaked it and is still questionable as described. I could then add the
>same amount to my coating solution and see what happened. This assumes an
>awful lot, in that the oxalic acid added to solution would not be used or
>restricted by the coating solution.
>
>The reason I revised your question ( made it my own) was that I see it
>either as an oxalic acid issue somehow acting on the ferric to ferrous
>equation or it is a pH issue and a lower pH somehow allows for a more
>complete reaction between the metal salts and the ferrous ions generated by
>the addition of UV light to the coated paper. Leaning strongly toward the
>former, I made suggestions towards that end. I can see however, from your
>further clarification, that you appear to be matching the acid to the
>developer to see if it somehow compliments that reaction.
>
>
>
>
>Eric Neilsen Photography
>4101 Commerce Street
>Suite 9
>Dallas, TX 75226
>http://e.neilsen.home.att.net
>http://ericneilsenphotography.com
>
>
>> -----Original Message-----
>> From: Sandy King [mailto:sanking@clemson.edu]
>> Sent: Thursday, August 11, 2005 2:09 PM
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: RE: Pt./Pd. question acid pre-soak
>>
>> Eric,
>>
>> You are absolutely right. My ferric oxalate solution has a pH below 2.0.
>>
>> I made a big mistake in relating what I did. What I meant to say was
>> that I added oxalic acid to the potassium oxalate developer in
>> amounts to get it into the pH 5.8 range.
>>
>> I have always added oxalic acid in excess up to about 5% to my ferric
>> oxalate solutions. In other words, I mix the basic ferric oxalate
>> solution form powder (I am currently using the Artcraft version), and
>> after mixture add about 5% oxalic acid on a weight to volume basis. I
>> did test the addition of oxalic acid over a fairly wide range, from
>> slightly in excess up to about 10% in excess, but all that really
>> seems to matter is that it be slightly in excess. Certainly more than
>> 5% is pointless. I did not, however, test the pH of the ferric
>> oxalate during those tests.
>>
>> I apologize for the confusing comment.
>>
>> Sandy
>>
>>
>>
>> >Sandy,
>> >Your ferric oxalate has a standard pH of 6.5? I shall need to go back
>> into
>> >my data sheets for confirmation on this but I believe that mine is down
>> in
>> >the 2 range. Did you start with B&S powder or a Formulary liquid? Other?
>> >
>> >Eric Neilsen Photography
>> >4101 Commerce Street
>> >Suite 9
>> >Dallas, TX 75226
>> >http://e.neilsen.home.att.net
>> >http://ericneilsenphotography.com
>> >
>> >
>> >> -----Original Message-----
>> >> From: Sandy King [mailto:sanking@clemson.edu]
>> >> Sent: Thursday, August 11, 2005 12:19 PM
>> >> To: alt-photo-process-l@sask.usask.ca
>> >> Subject: RE: Pt./Pd. question acid pre-soak
>> >>
>> >> Eric,
>> >>
>> >> I ran the same tests, i.e. adding extra oxalic acid to the ferric
>> >> oxalate. I don't remember exactly how much I added but I did test
>> >> the pH with varying amounts added, and although the pH of oxalate
>> >> solution changed from 6.5 down to below 5.8 I did not observe any
>> >> increase in Dmax.
>> >>
>> >> Sandy
>> >>
>> >>
>> >>
>> >>
> > >>
>> >>
>> >> >Kerik, How much "extra" oxalic acid did you try adding to the ferric
>> when
>> >> >you ran those test? And were you able to check the pH of the solution
>> >> after
>> >> >adding it?
>> >> >
>> >> >Eric Neilsen Photography
>> >> >4101 Commerce Street
>> >> >Suite 9
>> >> >Dallas, TX 75226
>> >> >http://e.neilsen.home.att.net
>> >> >http://ericneilsenphotography.com
>> >> >
>> >> >> -----Original Message-----
>> >> >> From: Kerik [mailto:kerik@kerik.com]
>> >> >> Sent: Tuesday, August 09, 2005 11:17 AM
>> >> >> To: alt-photo-process-l@sask.usask.ca
>> >> >> Subject: Re: Pt./Pd. question acid pre-soak
>> >> >>
>> >> >> With certain (apparently) highly buffered papers like Fabriano
>> >> Artistico
>> >> >> Extra White, it is absolutely true. And just adding oxalic to the
>> >> ferric
>> >> >> didn't have the same effect. Other papers that aren't as buffered
>> will
>> >> >> show little or no change after being soaked in oxalic acid.
>> >> >>
>> >> >> Kerik
>> >> >>
>> >> >>
>> >> >> >> 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.
Received on Thu Aug 11 16:23:37 2005