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?

I'll second my thought about acidifying paper for pt/pd or other iron

It's better to use hydrochloric or acetic acid for that purpose. The salt
you'll get from oxalic acid + calcium carbonate (the alkali buffer) is
calcium oxalate -> a highly insoluble salt with a needle-like sharp
crystal structure whereas both the salts you get from HCl and acetic are
highly soluble (= will leave the paper in the subsequent water rinse).

I use 5% hydrochloric acid for two minutes with Fabriano Artistico (Trad.
and EW) with very good results - regardless the batch number. I suspect
even one minute will suffice (no bubbles after about 30secs) but I keep it
in the acid batch a little longer for extra safety.

Probably finding HCl is easier (and cheaper) than finding oxalic acid too;
just ask for muriatic acid in the hardware store. I won't talk about
acetic acid -> everyday kitchen item. Anyway, the main issue is not
convenience here but sanity of paper / image in the long term. I don't
believe oxalic is a good idea...


28 Mart 2009, Cumartesi, 3:47 am tarihinde, Clay yazmış:
> 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..?
>> Paul
>> ----- 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...
>>>> Paul
>>>> ----- 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.
>>>>> Dan
>>>>> info@DanBurkholder.com
>>>>> www.DanBurkholder.com