U of S | Mailing List Archive | alt-photo-process-l | Re: Oxalic Acid Presoak for some pt/pd papers?

Re: Oxalic Acid Presoak for some pt/pd papers?

Cook and look. That's about the best advice I can give.

I don't know if it is possible to over-acidify, but it sure is obvious when it is under-acidified. The prints are weak and washed out.
On Mar 27, 2009, at 8:05 PM, Paul Viapiano wrote:

Good point, Clay...so far I've needed low dilutions, but I'll keep this in mind for the future.

There's no way to tell ahead of time, is there? Just make a print and have it be sucky, I guess..?


----- Original Message ----- From: "Clay" <wcharmon@wt.net>
To: <alt-photo-process-l@usask.ca>
Sent: Friday, March 27, 2009 5:52 PM
Subject: Re: Oxalic Acid Presoak for some pt/pd papers?

Paul's suggestions are all on the mark. I would like to add a footnote to item #3:

You may need concentrations of oxalic of 5 or even in some cases 8-10% to get rid of the buffering agents in Fabriano. This paper's buffering can be highly variable. I am still printing from a batch I bought about three years ago, and a 5 minute soak at 2% works fine. Some of the more recent batches I have used in workshops have needed 7.5% for 15 minutes! In short, YMMV. It is a great paper, as long as the buffering has been neutralized. The trick is in finding out exactly how much acid and time is needed for the batch you happen to have.
On Mar 27, 2009, at 6:34 PM, Paul Viapiano wrote:

Dan, I'm sure others will chime in but my findings are:

1. Fabriano EW, Arches Cover, Rives BFK, Stonehenge

2. Helps with better dMax, and general tonality, etc...so much of today's papers are so alkaline, heavily buffered, etc that the acidic pt/pd solution hits the alkaline paper and poor results occur.

3. 1 - 1.5% oxalic acid in water for 3-5 minutes...Stan Klimek also recommends this in the Arentz addendum. I dry flat on paper towels, but hanging is ok. I just don't want my corners marked with clips.

4. The Arentz book hasa whole chapter on paper; which ones are good to go as is, which need acidification, etc...

Fabriano EW is my choice with excellent results. Platine is a great paper, but I've never produced the same or as good results as the Fabriano.

After acidification, the single biggest tip is to humidify the dried, coated paper pre-exposure, and after you put the neg/paper sandwich in the frame, cover it with a piece of mylar the size of the frame before you put the back on and lock it up. Keeps the humidity in the paper during exposure and wow...! That made all the difference in my printing (also from Stan Klimek)...

Hope this helps...


----- Original Message ----- From: "Dan Burkholder" <fdanb@aol.com>
To: <alt-photo-process-l@usask.ca>
Sent: Friday, March 27, 2009 4:07 PM
Subject: Oxalic Acid Presoak for some pt/pd papers?

Sorry if this has been beaten to death on the list already but a Spanish friend wants the particulars of using a weak Oxalic acid presoak for some of his pt/pd printing. He's running into some monster- long exposure times as he prints on hand-coated inkjet papers. He has his reasons for doing this. Frankly, I'm impressed he's getting the results he is using a paper that isn't formulated for any kind of wet process. He hasn't checked the pH of the paper and that seems like a good place to start. In the mean time...

Here are some questions to stir discussion:

1. What papers are noted to benefit from the acid presoak?

2. What problems (lower D-max, mottling, etc.) does the presoak address?

3. What are the recommended acid dilutions and times and drying procedures for this procedure?

4. And anything else that you think would help.

I've never done the presoak thing but I am curious as to what others have to say about it.

Thanks in advance for any help and suggestions.