U of S | Mailing List Archive | alt-photo-process-l | Re: Eliminating CaCO3 in buffer in "achival" watercolor papers

Re: Eliminating CaCO3 in buffer in "achival" watercolor papers

Hi Loris,

Indeed, acetic acid might be a good solution to your problem. Regular
houshold vinegar (usually a 4% acetic acid solution) will probably do
just fine.
Calcium acetate indeed has good solubility characteristics in water.
There are more products that will result in water soluble salts to
clear any CaCO3, but they probably will ruin your paper, or are very
damaging to your health (HCl, HBr, Benzoic acid, chromic acid, to name
a few...).

According to my chemical books from university (I studied chemistry),
acidic acid is by far the most preferable option. And household
vinegar is the easiest form it comes in :-)

kind regards,


2008/8/12 Loris Medici <mail@loris.medici.name>:
> I've just read somewhere that calcium acetate (the salt of calcium
> carbonate with acetic acid) is also quite soluble. So, I may try a mild
> solution of acetic acid instead of HCl too...
> Regards,
> Loris.
> 12 Ağustos 2008, Salı, 1:29 pm tarihinde, Loris Medici yazmış:
>> Thanks Diana,
>> I also thought about citric acid but the product is insoluble Calcium
>> Citrate (a food additive), thus, it remains in the paper. I'd prefer
>> something that totally leaves the paper. Calcium citrate may interfere
>> with the process I intend to use - maybe that's why you didn't get perfect
>> results...
>> Thanks again,
>> Loris.
>> 12 Ağustos 2008, Salı, 9:16 am tarihinde, dhbloomfield@bellsouth.net
>> yazmış:
>>> Hi Loris,
>>> Not a chemist here, but I also had a horrible time trying to soak
>>> Fabriano
>>> in oxalic acid, specifically in preparation for pt/pd printing. Seems
>>> like I had to be extremely precise with everything; otherwise it was a
>>> disaster. I could never get it consistently even (the soaking, the
>>> amount I used, or something). Anyway, something came up about this once
>>> in
>>> a conversation with Mike Ware. He said that he thought oxalic acid was
>>> the wrong way to go, and he believed citric acid would be a much better
>>> choice-- and gave all the reasons why. That was some time ago, but if I
>>> can find that email, I'll forward it on. So I did try the citric acid,
>>> and it worked much better, though I never got an idea of the right
>>> amount
>>> to use, how long to soak, etc-- so it was never perfect (though 100
>>> times
>>> better than the oxalic acid soak).  I got busy and on to something else
>>> and never continued with it. or followed up about exact amounts, etc.,
>>> but
>>> it did work.