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 13:09:33 2005