Sodium thiosulfate fixer smell - whew!

Steve Goldstein

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Today I did an experiment I've been wanting to do for quite some time, comparing my regular paper developer (Ansco 130 1+1) with Michael A. Smith's enlarging-paper Amidol developer. I exposed a sheet, cut it in half, and developed one piece in each of the developers for 2 minutes. To get my workflow close to Michael's I used:

an acetic acid stop (48ml of 28% Acetic acid solution per liter)

a first fix of the "nearly odorless" variant of Kodak F-24 from The Darkroom Cookbook 4ed (240g/liter Sodium thiosulfate prismatic "rice" crystals, 10g/liter Sodium sulfite, and 22g/liter Citric acid)

a second fix of plain hypo (240g/liter Sodium thiosulfate).

These formulae are all very close to those Michael gives on his web site. Even before I added the Amidol powder into the developer tray containing the remainder of the premixed ingredients I noticed a sharp odor in my poorly ventilated darkroom, and after 20 minutes I had a headache. The effect of the odor was considerably worse than the vinegar smell of Acetic acid stop, which I can tolerate but nowadays avoid by using a Citric acid stop when printing.

Is this usual with Sodium thiosulfate fixers? I normally use a rapid fixer, either Ryuji Suzuki's neutral fix or Ilford Rapid Fixer 1+4. Their very faint ammonia smell is much less objectionable than what I encountered today. Unfortunately, improving my darkroom ventilation is a near-impossible task. Fortunately, the difference in the dried prints was so minor that I'm not likely to bother with Amidol again and will probably sell what I've got.
 

Mike Lopez

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I've never had a strong smell come from using sodium thiosulfate. A few questions:

1. You say "even before I added the Amidol powder..." To be clear, you suspect that the odor is coming from your fixer tray (with the sodium thiosulfate) and not the developer, correct? Are you implying that there's any relationship between the dosing of the amidol and the odor you noticed?

2. Is your acetic acid stop bath properly diluted? If you accidentally use undiluted glacial acetic acid, it would be no surprise that you quickly got a headache.

3. Michael's fixer formula does not call for citric acid. Could the addition of citric acid to his formula be the source of the odor?

4. Concerning your amidol, is it the Chinese stuff? What color is your developer solution after the amidol is added?
 

john_s

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Is there a specific reason to add acid to the fixer? An acidic fixer will smell of SO2. Closer to neutral will minimize the smell without adversely affecting the fixing. But maybe there's a specific reason to use acid in this case?
 
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Steve Goldstein

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Yes, I had premixed all the other developer ingredients and the Amidol powder was sitting in a small plastic cup. That stuff was all odorless. I believe it was the fixer.

2. Is your acetic acid stop bath properly diluted? If you accidentally use undiluted glacial acetic acid, it would be no surprise that you quickly got a headache.
Click to expand...

Yes, I don't keep glacial around, it's diluted it to 28%.

3. Michael's fixer formula does not call for citric acid. Could the addition of citric acid to his formula be the source of the odor?
Click to expand...

I didn't use exactly Michael's fixer formula, but Kodak F-24 was very similar. The Darkroom Cookbook 4th edition says that substituting Citric acid for the offical formula's Sodium bisulfite will "eliminate much of the odor associated with fixers".

4. Concerning your amidol, is it the Chinese stuff? What color is your developer solution after the amidol is added?
Click to expand...

It's English Amidol that I got from Artcraft some years ago, stored in the deep freeze since receipt. The powder was dark grey. I can't say what color the mixed developer was because I happened to use black trays for it. But the odor was there before I added the Amidol to the other already-mixed developer ingredients.
 
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Steve Goldstein

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I just double-checked Michael’s formulae. My stop bath was, if anything, slightly weaker than his. He calls for 50cc 28% Acetic acid per quart, I used 48cc/liter.

His first fix is “8oz dry measure” Sodium thiosulfate crystals plus 12.5g Sodium bisulfite per quart. I’ll have to figure out the weight equivalent of the thiosulfate.

Thanks for the tip about Lloyd’s pages, I’d forgotten about them.
 

Rudeofus

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Steve Goldstein said:
I didn't use exactly Michael's fixer formula, but Kodak F-24 was very similar. The Darkroom Cookbook 4th edition says that substituting Citric acid for the offical formula's Sodium bisulfite will "eliminate much of the odor associated with fixers".
Click to expand...
I don't have that book, but does TDC4 really suggest to use 24g Citric Acid instead of 25g Sodium Metabisulfite???

If this fixer had a sharp pungent smell, it was an extremely dangerous mixture. Sulfur Dioxide is very toxic.
 
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Steve Goldstein

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Yes. Here's the TDC4 Formula #138 for Kodak F-24 fixer:

Water at 125F/50C - 500.0ml
Sodium thiosulfate - 240.0g
Sodium sulfite - 10.0g
*Sodium bisulfite - 25.0g
WTM - 1 liter

* Substituting 22.0 grams of Citric acid for the bisulfite will eliminate much of the odor associated with fixers.
 
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Steve Goldstein

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Thanks, that thread makes for interesting and scary reading. In my case I used the pentahydrate so at least the I had the correct amount of Sodium thiosulfate.

I rarely write in books, but in this case I made an exception to strike out the Citric acid substitution.

BTW, this same suggested substitutiin also appears in TDC3. Don’t do it!
 
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Anon Ymous

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IMHO, it has nothing to do with pentahydrate vs anhydrous, but pH level alone. If you go too low, sulfur dioxide will be released.
 

Doremus Scudder

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FWIW, there's no reason you can't just use your Ilford Rapid Fixer or whatever else for your first fix. I don't think a sodium thiosulfate fix is a requirement with Amidol, or?

Anyway, there are other, less obnoxious fixers out there than F-24 that use sodium thiosulfate, if that's needed for some reason. Look for a non-hardening one.

Doremus
 

Rudeofus

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Anon Ymous said:
IMHO, it has nothing to do with pentahydrate vs anhydrous, but pH level alone. If you go too low, sulfur dioxide will be released.
Click to expand...
I agree with you, the issue is not the type of Sodium Thiosulfate, but that the amount of Citric Acid in this formula is excessive. I contacted Bill and Steve about this, they will hopefully chime in soon.
 

Anon Ymous

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Rudeofus said:
I agree with you, the issue is not the type of Sodium Thiosulfate, but that the amount of Citric Acid in this formula is excessive. I contacted Bill and Steve about this, they will hopefully chime in soon.
Click to expand...
Perhaps 2g is all that is needed and 22 is a typo?
 

Steve Anchell

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Rudolf Leitgeb made me aware of this post and the earlier 2004 post in photo.net. Thank you Rudolf.

In the 2004 photo.net post, Danny Spence wrote:

"The formula seems simple enough with only three dry chemicals -- sodium thiosulfate, sodium sulfide, and sodium bisulfite."

Mr. Spence indicates that he used sodium sulfide. The correct chemical is sodium sulfite. If he did use sulfide this would account for the discoloration and sludge. I have looked at all 4 editions of the DCB and sodium sulfite is specified.

In the second thread (in which only an offensive smell is mentioned) I concur with the conclusion of several respondents to eliminate both the bisulfite and citric acid from the formula. Bisulfite was included in the original formula before papers were sufficiently hardened. Acid is no longer needed and for that matter hardener of any kind, as most papers are over-hardened for machine processing. Those that are not over-hardened still contain more hardener than papers prior to the 1990s.

At the time the first edition of the DCB was written I was using F-24 for large format pyro negatives. I later switched to TF-4 alkaline fixer with a 1 minute running water rinse in place of a stop bath, thereby eliminating both the acetic acid stop and hardener in the fixer. I now use TF-4 for film and paper.

I never tried substituting citric acid in F-24 as I never had a problem with odor and have always tried to minimize the use of hardeners.

My apologies to both Mr. Spence and Mr. Goldstein for having discovered this the hard way, but thank them for sharing with the rest of us. I have just crossed out the citric acid in my mark-up copy of the DCB, as per Mr. Goldstein's recommendation.

Feel free to post these issues on the DCB forum and I will be more likely to see them and respond.
 

Anon Ymous

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At the aforementioned photo.net thread, the OP made a typo, which he confirmed and asked for the post to be edited. He used sulfite.
 

billtroop

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This thread brings up several points for me.

1. Although citric acid was considered by Kodak a just-acceptable substitute for a stop bath during the period of acetic acid shortages in the 1940s, no fixer was published with citric acid and I would not use it in a fixer. I wouldn't use citric acid in a stop bath either, as FDC2 (141) makes clear, but I accept that it has been growing popular for this purpose in recent years. If I were using a citric acid stop bath, I would rinse in plain water afterwards, before the fixer.

2. It is seldom mentioned when F-24 is used, but Haist p. 573 notes, "The reserve acidity of the sodium bisulfite is insufficient to maintain the pH of the solution with continued use. If such a fixing bath is to have a long life, its acidity must be maintained by either continuous addition of sodium bisulfite solution or replenishment at regular intervals." -- Steve, I don't think either of us ever mentioned this in connexion with F-24, and we should.

3. The pH range of acid fixing baths is narrow. Formulating a fixing bath is not easy.

4. Citric acid should not be present where an acid hardening system is used in the fixer.

5. Acetic acid is the best acid discovered for acid stop baths and acid fixers. However, Haist (576) highlights Crabtree and Hartt's observation in 1929, that a perfect acid for these purposes has not yet been found.

6. It seems apparent from at least three threads that dumping citric acid into a thiosulfate solution may result in precipitation. I don't know what the history is of the suggestion that citric acid be used in F-24 instead of bisulfite. I have no doubt that it has worked for some at some point in the past, but it seems predominantly not to be working now. That could be due to any number of factors: mixing order, a possible error in the formula as Rudi has suggested, different grades of chemicals, or something else.

7. If I wanted a non-hardening acid fixer that was as alkaline as practical, I would make F-6 but without the potassium alum. Advantages would be lower odor and faster washing.

8. Thiosulfate is more stable in neutral to alkaline solution.
 

mshchem

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The standard Kodak F5 powdered fixer stinks horribly.

Why not follow Ilford recommendation, citric acid stop bath (Ilford stop) followed by Ilford Rapid fix. Follow the Ilford archival procedure. Easy.

Kodak F6 is a much lower odor sodium thiosulfate hardening fixer.
 

Anon Ymous

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Why use a hardening fixer? For the vast majority of cases, it doesn't offer anything at all, but makes washing harder. Using a neutral non hardening rapid fixer is the best choice for performance and low odour. If scratch mixing is preferred and ammunition thiosulfate isn't readily available, a sodium thiosulfate plus ammonium chloride fixer is almost as good.
 

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Steve Goldstein

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It's always amazing to me how quickly threads drift off-topic.

I started this thread because of a problem I encountered using the alternate version (Citric acid instead of Sodium bisulfite) Kodak F-24 formula in TDC4 to compare Amidol and Ansco 130 as developers for standard enlarging papers. I used this formula because I didn't have any Sodium bisulfite on hand (some is now on its way to me). I was not interested in using it with hardeners. Yet the discussion has sailed off in this direction.

The important point of my initial post has been accomplished, though. The suggestion of substituting Citric acid in the F-24 formula found in both TDC3 and TDC4 (and perhaps earlier versions, I only have 3 and 4) has been confirmed as being both WRONG and DANGEROUS. I suggest that owners of TDC take a pencil RIGHT NOW and strike through that asterisked note to remove the temptation to try it.
 

konakoa

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Good grief, that posting on photo.net was one I made ages ago. A bit shocked to see someone still reading it all these many years later. To the OP and anyone else who sees this; I've been using a straightforward two component sodium thiosulfate (pentahydrate/ctrystals) and sodium sulfite (-ite! that stupid typo is still causing problems I see!) combination to make a simple paper fixer in my darkroom since 2004. Commercial rapid fixers with the ammonia are just too powerful a smell especially in large trays. The same for glacial acidic stop baths. I've been using citric acid instead for stop. For film I do still use commercially made ammonium thiosulfate rapid fixers.

I've had no problems whatsoever with sodium thiosulfate for my fix and citric acid as the stop bath in my printing process. There's no to barely any detectable smell with these solutions, and my prints all these years later are still perfectly processed. I especially like the lack of any odor of these solutions, but primarily as I mix the solutions fresh right before printing and don't store them afterwards. I always have good chemistry that way and don't second guess if something is exhausted.
 
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