[Alt-photo] Re: Sulfamic Acid for Paper Acidification

[Jeremy Moore]

Clay, I was wondering the same thing about using it as a clearing bath.
Please report back if you test it. It's always great to reduce the number
of chemicals we need to keep on hand!

- Jeremy


On Sun, May 5, 2013 at 2:39 PM, clay at clayharmon.com <clay at clayharmon.com>wrote:

> Serdar,
>
> Thanks for this comprehensive summary. You can be sure I am going to use
> this for my next batch of paper that needs to be acidified.
>
> Your description also made me wonder if anyone on the list has tried
> sulfamic acid as a clearing agent for platinum and palladium. I have
> occasionally run into some very absorbent papers that seem to stubbornly
> hold onto the residual ferric oxalate sensitizer, and in those cases have
> often resorted to a bath of either dilute HCl or dilute phosphoric acid to
> clear the paper.
>
> Like others have mentioned, storing a bottle of HCl in your darkroom is an
> invitation for all sorts of corrosion issues. I store mine outside the
> house for this reason. The sulfamic acid sounds ideal for use as a clearing
> agent in the first clearing bath or two, followed by something a little
> gentler. I suspect that the sulfamic would probably produce some H2S
> (stinky!)  if you took the paper directly from the acid to a sodium-sulfite
> based hypoclearing bath. But I would guess that you could minimize that
> with a clean water rinse in between.
>
> -Clay
> On May 5, 2013, at 3:11 PM, "Serdar Bilici" <sbilici at gmail.com> wrote:
>
> > Hi Christina,
> >
> > I have listed my observations and thoughts on the acids I have tested for
> > paper acidification (and one acid I haven't tested). I did not include
> these
> > in the initial post, because I do not want to start a debate on everyones
> > favorite acid for paper treatment.
> >
> > And as Loris pointed out the evaluation depends on the process. My
> > observations are based on the new cyanotype, argyrotype and VDB (I used
> it
> > as a control to observe if there has been any improvement with the paper
> in
> > general).
> >
> > Sulfamic Acid vs Hydrochloric Acid (HCl)
> > -Both are equally strong acids, both are ph 0 at 1M solutions
> > -Reactions with both acids produce highly water soluble byproducts
> > -HCl evaporates easily, so it is hazardous to use without proper
> > ventilation, it has irritating odor.
> > -Sulfamic acid has no odor, I have not come across any warning on SA
> fumes.
> >
> > HCl treated papers produced weaker dmax with the new cyanotype and
> > argyrotype. I must say I had deeper blues with the same papers using
> > traditional cyanotype formula. Papers were definetely clear of buffer but
> > did not perform well with new cyanotype, argyrotype and even with VDB.
> > Anyway, that was the turning point that I decided to look for another
> acid,
> > otherwise there was no point in making prints with such poor dmax.
> >
> >
> > Sulfamic Acid vs Citric Acid
> > -Citric acid is weaker compared to sulfamic acid, I have not tested its
> > capacity but theoratically it will exhaust faster than sulfamic acid.
> > -1M CA solution has ph of 5 (source: internet), SA has 0.
> > -Reaction with citric acid produces, water insoluble calcium citrate
> inside
> > the paper. In dry form it is a white powder substance. I have not noticed
> > its presence even with the thinnest papers that I have tested. (200gsm
> FATW
> > and 180gsm Schoellerschammer)
> > -To prepare 1M 1lt citric acid solution 192 grams of acid is needed, 1M
> 1lt
> > of Sulfamic acid requires only 97 grams. Roughly it is double the amount
> for
> > a considerably weaker acid. Their costs per kilograms are similar.
> >
> > I started experimenting with citric acid at the same time, I started
> testing
> > sulfamic acid. Citric acid results were definetely far better than HCl,
> they
> > were as good as my initial results with SA (for new cyanotype and
> > argyrotype), but I did not continue testing it. Because double the
> amount to
> > prepare 1M solution which is far weaker in acidity and who knows how few
> > papers it would neutralize seemed too costly. If I was going to spend
> such
> > money on acids, I would rather spend it on cheap but reliable awagami
> masa
> > paper and order some from USA. That is why I stopped testing citric acid,
> > and continued with sulfamic acid.
> >
> > So I must clarify, citric acid works quite good too, but it is too
> costly to
> > justify IMO.
> >
> > Sulfamic acid vs Acetic Acid/Vinegar (Rather, why I haven't tested it)
> > -Vinegar is unreliable due to additives IMO, and the acidity changes from
> > brand to brand
> > -I did not want to try concentrated acetic acid due to its strong
> irritating
> > odor.
> > -Acetic acid is also a weak acid (around ph4 as I recal)
> > -But byproduct of reaction is highly water soluble calcium acetate,
> which is
> > great.
> >
> > That was it actually, why I haven't even tested acetic acid/vinegar.
> Strong
> > odor, weak acidity and probable cost due to its weakness.
> > I know some people use vinegar or acetic acid, and if it works for them
> that
> > is great , but cost wise, I find SA to be a better choice.
> >
> > Sulfamic Acid vs Oxalic Acid
> > -Oxalic acid is a strong acid (I haven't measured it, wiki says it is
> > stronger than acetic acid), but SA is stronger, has a ph of 0
> > -1M 1lt OA solution requires 126grams of acid. 1M 1lt SA requires 97grams
> > -The reaction produces water insoluble calcium oxalate crystals inside
> the
> > paper. Calcium oxalate is soluble in EDTA.
> >
> > Although,  oxalic acid is probably the most popular acid recommended for
> > neutralizing buffer, these crystals are a considerable problem for
> processes
> > that does not involve a EDTA wash step.
> >
> > These crystals were not noticable with thick papers (CansonMontval
> 300gsm or
> > Gvarro 420gsm), but thin hot pressed papers like FabrianoArtistico TW HP
> > 200gsm and Schoellerschammer 180gsm practically turned to sand-papers.
> > Especially after coating new cyanotype, I think the crystals become more
> > pronounced (may be from the oxalate in new cyanotype chemistry, just a
> wild
> > guess). So, OA treated thin hot pressed papers became useless IMO, and
> not
> > just for new cyanotype or argyrotype. As long as there are crystals on
> the
> > surface it is useless for  any process.
> >
> > The prints had satisfactory dmax, although the surface of the paper was
> > filled with tiny white crystals. But the Dmax with new cyanotype on 200
> gsm
> > FATW HP and on CansonMontval were not good as the dmax I got with
> sulfamic
> > acid. I must mention FATW HP is a quite a poor performer among all the
> > papers I have tested even with VDB (before and after SA treatment). But
> the
> > actual problem was the presence of shiny white crystals poking out from
> the
> > paper.
> >
> >
> > Considering all these,
> > I had best dmax with sulfamic acid treatment for new cyanotype,
> argyortype.
> > There is a slight increase in dmax with VDB too and shift in color
> towards
> > cooler maronish browns.
> > There is no insoluble byproduct in paper, no nasty odor. It has strong
> > acidity and it is cheap. It can be stored indefinetely in powder form
> and it
> > has a great capacity (1M 3lt would neutralize 45 full sheets).
> >
> > These are the reasons why I considered sulfamic acid to be a better
> choice
> > of acid for paper acidification.
> >
> >
> > P.S. Feel free to correct me, I have written a lot of chemistry stuff
> and I
> > am quite a newbie at such things.
> >
> > Best Regards,
> > Serdar
> >
> >
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