Sulfamic Acid for Paper Acidification

[Herzeleid]

Approximately two months ago, I needed to find a way to neutralize the alkaline buffer in some papers so I could practice with the new cyanotype and the argyrotype processes. In this period I have tried various acids such as hydrochloric acid, citric acid and oxalic acid. I have experimented with sulfamic acid to use for paper acidification and neutralization process, which I believe to be a better choice of acid than the most.

I heard this acid for the first time in Mike Ware’s argyrotype formula. I am no chemist by the way, but I noticed that sulfamic acid is quite a strong acid when I tossed a spoonful of it into the sink (don’t ask why). Within less than a minute I heard that it started fizzing loud, I washed it away hastily. Then I have decided to read and learn about the sulfamic acid and its uses, because I needed an acid to neutralize the buffer in papers and sulfamic acid sounded (well, it fizzed) to be capable.

It seems that sulfamic acid is used in modern descaling systems instead of hydrochloric acid, due to its less corrosive and at the same time equally strong acidic nature. It is also used in paper industry as pulp bleach. It sounded quite ideal to me because of its use in paper making and less corrosive properties.

Let me list some of the advantages of sulfamic acid

• It is a dry, non-volatile, non-hygroscopic, white crystalline substance
• It is moderately soluble in water and forms a strong acidic aqueous solution
• It is as strong as mineral acids (I have measured Ph. of 1M solution as Ph. 0)
• It is less corrosive (safer to use with stainless steel and uncoated iron materials, unlike HCl)
• Due to its non-hygroscopic nature, it can be stored in powder form indefinitely
• It is odorless! (yep it is)
• The reaction with the papers’ alkaline buffer produces only C02 gas.
• The reaction’s byproduct is highly water soluble calcium sulfamate (I cannot find solubility measurements of calcium sulfamate, but it is often referred as highly soluble in water in some articles)

I do not want to discuss in length problems with the other acids I tested for paper acidification, but suffice to say some of these problems forced me to look for an alternative. Sulfamic acid treatment causes no water insoluble solid byproduct inside the paper. There is no hazardous gas release during the process, or any respiratory irritant odor. It is cost effective and neutralizes the buffer completely with no loss of image quality.

Using sulfamic acid, I believe the treated papers become suitable for every alkaline sensitive siderotype, not just pt/pd and show no loss of dMax. I have tested various papers such as 300gsm Canson Montval, 420gsm Gvarro, 180gsm Schoellerschammer dura matt, 200gsm Fabriano Artistico Traditional White HP, 300gsm Fabriano Artistico Extra White SP, I happened to have a small piece of Hahnemühle Copplerplate warm white 300gsm and I also tested some cheap schoeller and alex drawing papers. All these papers were alkaline buffered and after treatment they all work well within expectations.

The acidification procedure is very simple and straightforward. I mixed 1M solution of Sulfamic Acid (97gr/mol), if you prefer it non-molar terms it is ca. %10 solution. 1 liter 1 molar solution of SA is approximately capable of neutralizing 50gr. of calcium carbonate. We can assume it would neutralize 20 sheet (56*76cm) paper’s buffer if we assume a sheet of paper contains 2 to 2,5gr of calcium carbonate (Thanks to Loris for providing me all these data on chemical equations and ISO9706 papers). To be safe use less number of papers, I assumed that 1lt 1M solution is capable of neutralizing 14 to 15 papers alkaline buffer safely. There is no need to emphasize the gloves and adequate ventilation, because it is always the right thing to do. Sulfamic acid is as strong as HCl, but less corrosive to metals.

I immersed the papers in SA solution for 15-20 minutes, flipping the paper 4-5 times during this wash. Of course, the length of this period will depend on the paper used. Loris noticed the reaction continues after 15minutes with 300gsm FAEW SP, and I observed the same. But with 300gsm Canson Montval, 420gsm Gvarro and 200gsm FATW HP the reaction seems to finish around 10-12 mins. Anyway, later I have decided to wash all these papers for 20minutes to be on the safe side, and I did not observe any adverse effects.

After acidification, I washed the papers (5 of them in the same tray) with tap water (chlorinated, not filtered, measured Ph. 7), for 20-25 minutes with 4-5 changes of water, and with each change of water shuffling the papers and bringing the bottom one to the top. When finished washing, I hanged the papers to dry in the bathroom.

The New Cyanotype process: As expected the sensitizer does not require additional citric acid to use with SA treated papers. The papers become chemically pure enough for new cyanotype. Adding CA to sensitizer even lowers dMax and shifts the color slightly. I have left coated paper (without CA) due to power outage for more than 12 hours and there was negligible fogging (24C %60-65RH). The amount of ilfotol depends on the paper, but I have found for Canson Montval and FATW 1drop of ilfotol per ml, for FAEW SP 2drops of ilfotol per ml work best for me.
All the samples were produced in 25C %55RH environment, printed with UVBL bulbs using non-linearized image-setter negatives. Initial wash for 1 minute in %1 sulfamic acid, then washed in tap water for 20mins.




The Argyrotype process: It worked flawlessly IMO. The sensitizer requires surfactant by nature. I have found that double the amount of ilfotol I used for new cyanotype works well for argyrotype. After determining the correct amount of ilfotol/tween I have noticed no bleeding. FAEW SP is particularly a hard surfaced paper it requires moderate humidity and quite a lot of tween or ilfotol in the sensitizer. For comparison I also included a sample printed on Masa paper, it works with new cyanotype, argyrotype and ziatype without any prior acid treatment.
All the samples were printed in 25C %55RH environment with UVBL bulbs using non-linearized image-setter negatives. Initial wash in %0.25 citric acid for 3minutes, %3 hypo for 1 min, then tap water 20mins.




Sulfamic acid treated papers work very well with the new cyanotype and argyrotype processes. And these processes happen to be the most finicky processes in all of alternative processes when it comes to paper’s chemical purity. I am confident that SA treated papers will perform quite well with the entire range of siderotypes.

And thanks to Loris for testing it, now I know it works flawlessly with ziatypes. I am sure he will share his thoughts on the subject as well.

I would very much like to hear your opinions on the subject, or if you see a way to optimize the procedure. And if you happen to try this acidification method to use with Kallitypes or DOP Pt/Pd I would like to hear your thoughts on the results.

P.S. I am grateful to Loris Medici for his support and guidance during this process. I could not have done it all by my own.

Best Regards,
Serdar Bilici

 

[Mike Wilde]

While not in a posotion to refute your outcome from independent testing, I laud your 'well, let's try it and calibrate the effort' thinking.

I almost don't like web resources like the massive development chart. I think it takes the considered review and reconsideration of the next round of trial and error out of the pickure.
I prefer to experiment and converge on the best solution for me. I might start with a commercially recommened optin as a starting point, but I always wander away to see what the sesnitivitires of the process are.

My only exposure to sulfamic acid to date was to see it in commercial tray claners I have used.

 

[Herzeleid]

While not in a posotion to refute your outcome from independent testing, I laud your 'well, let's try it and calibrate the effort' thinking.

I almost don't like web resources like the massive development chart. I think it takes the considered review and reconsideration of the next round of trial and error out of the pickure.
I prefer to experiment and converge on the best solution for me. I might start with a commercially recommened optin as a starting point, but I always wander away to see what the sesnitivitires of the process are.

My only exposure to sulfamic acid to date was to see it in commercial tray claners I have used.

Thanks Mike. I hope people will give it a go and we can enrich this topic, even improve the procedure.

After learning more about sulfamic acid, I also used it to clean my darkroom trays. It is very effective at removing crude and dried chemical remains.
Its effectiveness was the reason that I chose it to experiment with. And yet it was odorless, very easy to mix from powder and relatively safe.

 

[Loris Medici]

Hi all,

First of all I want to thank Serdar very much for his great (and elegant) idea + the hard work he endured in testing and putting it all together. It's one of the best tricks I've ever been made aware of since a long time...

Few notes:
- Very little SA goes a long way, the capacity of a (say...) 3l bath is around 45 full 22x30" 140lb paper (by Serdar's definition within safety limits), therefore it's both cost effective and generates less waste. (Presumably more environment friendly???)
- IT WORKS FLAWLESSLY! To me, it's hands down the best acidification method I've ever tried. I've tried oxalic acid, citric acid and hydrochloric acid before; this one's the method that gave the best results.

Try it for yourself.

Thank you again Serdar,
Regards,
Loris.

 

[Mike Ware]

My thanks and congratulations to Serdar Bilici for hitting on this idea and so thoroughly testing it. His step tablets speak for themselves.
I have never had to go down the road of paper pre-acidification, because I only use papers that do not contain chalk (calcium carbonate), such as Buxton and Herschel.
But I can see that this work does greatly extend the usefulness of my argyrotype and new cyanotype (and probably other siderotype) processes to a greater range of presently-available papers.
BTW, sulphamic acid can also be used for the first, acidic bath in new cyanotype, if nitric or hydrochloric acids are, for any reason, unacceptable.
Mike

 

[Herzeleid]

Thank you very much Mike. I am glad that you find the tablet prints satisfactory.
As you have said this method would extend the range of papers usable with argyrotype,the new cyanotype, and pop pt/pd. I haven't tested it but I believe SA treated papers would work well with all of the siderotypes. To me if it works with the new cyanotype and the argyrotype it would work with anything. Loris tested pop pd and it works with that process too.

I believe this might be especially helpful when learning/practicing and probably at teaching alternative processes. SA treatment opens up a whole range of commonly available and affordable papers to work with, not that they can replace alkaline and acid free hand-made papers.

I have prepared the new cyanotype samples using initial 1 min wash in %1 sulfamic acid, the results were so superior to initial citric acid wash IMO.

Regards,
Serdar

 

[Herzeleid]

Thank you Loris, I am grateful for your help and guidance in the matter.

I noticed that I haven't mentioned how long SA mixed in water will keep its strong acidic properties, it has been a few weeks there is no problem yet (It is still around Ph 1, and treated approx. 10 full sheets with it). But in powder form it would keep indefinitely in normal humidity and temperature. It is quite cheap so, I do not consider aqueous solution's shelf life to be an issue.

 

[Loris Medici]

Hi Serdar,

I remember reading somewhere that the solutions of Sulfamic Acid are quite stable too. Therefore one can mix the solution beforehand and use it whenever needed.

Regards,
Loris.

 

[Loris Medici]

...
I have prepared the new cyanotype samples using initial 1 min wash in %1 sulfamic acid, the results were so superior to initial citric acid wash IMO.
...

I would agree with that, cyanotypes (both traditional and new formula) change hue toward more green when treated in citric acid. Some may like it some may not... (I like it for new cyanootype but the results are too greenish to my taste for trad. cyanotype.)

Regards,
Loris.

 

[jakobb]

Commonly oxalic acid is recommended to acid treat paper but calcium oxalate is very insoluble - which never made sense to me (marble sculptures were often treated with oxalic acid to give them a protective shinny insoluble coating). I was wondering if it could be also used as a general clearing agent for all siderotypes. I am using mostly Pd and HCl is not useable. I am presently using citric acid and/or di Sodium EDTA as the first clearing baths.

 

[Herzeleid]

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.

 

[j_landecker]

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

 

[Herzeleid]

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.

 

[Herzeleid]

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.

Best Regards,
Serdar

 

[sklimek]

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

 

[Herzeleid]

Hello Stan,

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.

Regards
Serdar

 

[sklimek]

Hi Serdar,

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

 

[Loris Medici]

...
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

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...)

Regards,
Loris.

 

[Loris Medici]

...
It was DOP pt.pd. Yeah I agree Fabriano Artistico has the hardest shell of sizing I have ever had to deal with.
...
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.
...

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.)

Regards,
Loris.

 

[Herzeleid]

Hi Stan,

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.

Regards,
Serdar

 

[sklimek]

dMax of 1.30 is not great but acceptable in my world, clearly there is more experimentation that needs to go on to start fine tuning, loris do you do any pre-treatment to FAEW before applying the emulsion?

 

[Loris Medici]

Hi again Stan,

No special treatment other than the addition of 1 or 2 drops of glycerol (humectant) per ml to the coating solution, when I work <=50% relative humidity. With pop Pd, you need a certain amount of humidity in the paper for best results...

Regards,
Loris.

 

[jakobb]

I tried acidification with sulfamic acid on Zerkall book paper and did some Pd prints. This paper is only slightly buffered (close to neutral pH). Treatment with citric acid improves especially the mid tone but with sulfamic acid (0.5 M) pretreatment I got grainy highlights and mids (slightly better than untreated paper) but good dMax. Also the paper surface got softer so I was wondering if sulfamic acid is not only removing calcium carbonate but also interacting with the paper sizing.

 

[Herzeleid]

If the paper has gelatin sizing, due to considerable duration of acid and water washes it is possible imo that the gelatin sizing might be diminished or even removed completely.
Afaik, many water color papers now used AKD sizing, and it is impossible to effect AKD sizing with acid treatment, but I have no experience with Zerkall papers. I have no idea on its sizing.
I tested Hahnemühle's gravure paper with argyrotype, its surface was very delicate and the print easily abraded, because it has no sizing.

I added ilfotol to sensitizers (argyrotype, new cyanotype, VDB) with SA treated papers, may be it can help with grainy highlights. I have no experience with Pd, so don't take my word for it.

 

[sklimek]

I can report one of my favorite and more difficult papers to print on now is predictable, easy coating and a great black. Rives BFK a paper from the printmaking world as opposed to the watercolor world. I have only experimented with the 175 gsm but I have some 300 gsm coming in. But very happy that as far I can see at this point it will probably jump to the start of preferred papers for Pt/Pd. This was from using the 20/20 10% sulfamic technique. Thank you for sharing your testing.