As I have mentioned there were certain problems with commonly recommended acids to treat paper, calcium oxalate as one of them. Although, it can be dissolved to some extent in EDTA, insoluble remains adversely effected prints with thin hot pressed papers.
I have no clue if it can be used as clearing agent. The information on the internet points out that sulfamic acid is iron ligand, it forms water soluble calcium and iron(3) salts, if this helps.
Looks like it's readily available at hardware stores - in its MSDS this tile cleaner is specified as containing 100% sulfamic acid by weight: TileLab Sulfamic Acid Cleaner
If it is %100 percent sulfamic acid and it has no additives then why not, it should be easy obtain from hardware stores. I buy sulfamic acid from chemical supplier, it costs around $6,7 per kilogram. I searched online and found some online hardware stores that sell 1lbs (454 grams) packs around the same price. It can make a solution of 4.5 liters and it can neutralize approximately 60 full sheets 22"x30"(56x76cm). It is still cheap I guess.
I wanted to add something points that I have shared in alt-photo-process mail list here as well.
I have listed my observations and thoughts on some of 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 everyone's favorite acids.
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 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 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.
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)
-Byproduct of reaction is highly water soluble calcium acetate.
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.
Hi Serdar, thank you for your hard work and sharing.
I went down to Home Depot (local hardware store) and picked up a pound of sulfamic crystals and went to work based as a starting point using your recommendations of a 10% solution (454 grams SA to 4.5 liters water) with a soak/agitation for 20 minutes and a wash for 20 minutes. The paper was 200gsm (90lb.) Fabriano Artistico traditional.
Artistico was a favorite of mine a few years until it developed problems and I needed to find another paper. I agree with you that it has a very ‘hard size’ that needs to be broken down before it is printable and in the past I pre-treated FA with a 5% solution of oxalic acid for 10 minutes, no post wash. Also as in the past I used the back of the paper for coating, I never cared for the finely spaced parallel lines I see with a loupe on the recto side. Also, the backside just has a slight texture that I preferred.
I coated up two pieces of paper one with 3 drops of tween and one without tween and got back a measured dMax of 1.30 without tween and 1.26 with tween. Also, the paper coated up very even with the Richeson brush. I always use a reference print when I compare papers and my reference print is from ‘old’ Platine and found the Atistico had more contrast and a bit faster than the Platine with the same solution the contrast can be fixed with a slight tweeker curve if needed.
All in all I was very impressed by results, Artistico was un-printable for me before. In addition there are no irritating fumes to deal with (I heard the HCI was being used for awhile) which I would think could be very annoying especially if you are doing a large run.
I look forward to trying this on other paper as well!
Best - Stan
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First of all, I am so glad to hear that you have good results. Please share your thoughts if you test other papers. The list of papers and processes will start to grow I guess.
And was it pop PD or DOP pt/pd? I am curious to know with which processes SA treated papers work fine. Up to now, it is new cyanotype, argyrotype and ziatype that I am aware of.
I gather it was FATW hot pressed 200gsm, i dislike the parallel lines on the front side too, it is too regular (lacks identity IMO). I also prefer the back side of this paper it has a subtle texture and it does not overwhelm the image. 200gsm TW HP was slightly easier actually compared to FA 300gsm SP EW. It was the hardest surface, I have tested. It is problematic to work in arid conditions with that paper. I worked in %50-60RH environment, even under that conditions FAEW SP required too much ilfotol with argyrotype but it might be also related to the nature of the process. But compared to Canson Montval both FA papers definitely have harder surfaces.
But I agree after acid treatment and wash, it was easier to have a uniform coating with FA papers. I used DaVinci brushes when testing so I think I can relate to your experience with the Richeson.
Did the SA treated paper cleared easier or was there no difference?
And thank you for the good news.
It was DOP pt.pd. Yeah I agree Fabriano Artistico has the hardest shell of sizing I have ever had to deal with. It is a watercolor paper that was created for watercolor artists to keep pushing their liquid water color around with brushes and the sizing was designed for the artist to work without the paper absorbing and stopping the this creative action unlike printmaking papers that has little size for the etching presses.
I work with humidity quite a bit and actually put the paper into a humidity box at 80% for ten minutes before exposure. I found this injected for some/not all increases the dMax but will also make it a bit harder to clear. With your SA method we are literally stripping out all of the papers prepared sizing and starting with a pristine sheet of rag paper. It is more difficult to clear in that there is no sizing to prevent the emulsion into settling deep within the paper fibers.
In my clearing I do a 3 minute development – water wash dump (no reason to have the first clearing bath work so hard) and then do 4% muratic acid – EDTA – Citric acid – sodium sulfite all at 5 minutes each and it works well. The sodium sulphite is just two minutes. I like this acid – sulphite – acid attack.
Best - Stan
Wow, that's great news Stan, happy for you! It's significant to receive recognition from a master printer like you. The Dmax figure you quoted is a little bit on the low end though, telling me maybe there's still a a little more room for improvement - my pop Pd prints on FAEW SP are around log 1.4. (Don't have the actual measurement, I'm only eyeballing with reference prints with known Dmax readings...)
Originally Posted by sklimek
Hi again Stan, I don't think sulfamic acid does anything to the sizing of Fabriano papers; to my knowing those are sized with AKD, and sulfamic acid doesn't attack AKD. I haven't noticed a change in the absorption characteristics of the paper myself... (That's for FAEW SP.)
Originally Posted by sklimek
I forgot to mention one thing, I realized after reading Loris's comment. I have no experience with dmax measurements, so I am not sure how good is dmax of 1.3. But my experience with FA traditional white HP 200gsm was not great in terms of the deepest black. It gave the worst dmax in all of the papers that I have tested. I bought the paper because of its subtle texture and warm base but the results were not good. I only tested argyrotype, new cyanotype and VDB with that paper. FA Extra White SP 300gsm is definitely a better paper in terms dmax, the texture on the reverse side of this paper is also subtle. It is not so pronounced and does not overwhelm the image. I liked both sides of that paper.