D-23 and Stop Bath

koraks · Apr 4, 2024

Maybe you smell something that comes into contact with the citric acid solution. But the solution itself - nah, I find that extremely hard to believe, especially it being a dominant smell in your darkroom. Virtually everything has a stronger smell in a darkroom than a pure citric acid solution, including the worktop, the walls, any people present (including you) and the water that comes from the tap.

Of course, if you use it as a stop bath for prints, you'll carry some developer over into the stop bath. This developer contains sulfite, and some of this will break down into sulfur dioxide. This has a particular smell to it and it's quite strong/pungent. Perhaps you're mistaking this for the smell of citric acid. Or maybe your water has a high iron content and this is what you smell. The citric acid itself - nope.

pentaxuser · Apr 4, 2024

It seems that we still can't reach a definitive conclusion. Whatever it is, it seems to be enough to leave symptoms such as a sore throat and a nose that hurts to draw in air hours after the initial "shock"

I think we can safely assume that the OP has used citric acid at the correct dilution so what isn't clear to me is why citric acid at the correct dilution is sufficiently strong to create the effect that koraks refers to in terms producing sulphur dioxide. If it was then unless almost no-one uses it as stop bath for film then we've had heard of more complaints of this nature. I think we can safely assume that the OP has used citric acid at the correct dilution

What also isn't clear to me is why acetic acid at a very low percentage such as koraks suggested(0.5%) stops the the production of sulphur dioxide but citric acid at its proper dilution does not

Is there any reason why citric acid at a higher dilution than in normally the case would not do the same as acetic acid at 0.5%? If not what is the reason Is there an inherent difference between the 2 acids that makes only acetic effective in stopping the production of sulphur dioxide?

pentaxuser

MattKing · Apr 4, 2024

pentaxuser said:
It seems that we still can't reach a definitive conclusion.

A fairly likely result, when one is attempting to use the internet to solve a mystery relating to a smell

chuckroast · Apr 4, 2024

koraks said:
There's no way a citric acid stop bath will start smelling like vinegar. I think you're mistaking something else for a vinegar smell. What does happen is if you use a fairly strong stop bath after a high-sulfite developer like D23, is that sulfur dioxide will be formed. At a low pH (<4.0 IIRC), sulfite will break down into sulfur dioxide. There's plenty of sulfite in D23 and some of the developer is on your film & reels. I assume you're mistaking the pungent smell of sulfur dioxide with a vinegar smell - they really are quite different, but both are often experienced as pungent and 'nasty'.

You can fix this in a few ways:
1: Don't use an acid stop bath. At risk of starting yet another lengthy diatribe about yes/no stop bath, your film will really come out fine if you use only a water bath instead of an acetic acid stop bath.
2: Use a buffered citric acid (or other non-odorous) stop bath. You're not the first one to run into this problem and @Steve Goldstein solved it like so: https://www.photrio.com/forum/threads/buffered-citric-acid-stop-bath.201215/
3: Use...acetic acid! It's quite likely that you will find a weak (0.5% or so) acetic acid stop bath to be acceptable in terms of its smell. Since the pH will be higher, but still low enough to act as a proper stop bath, there will be no (or very little) sulfur dioxide gas being formed.

+100 on using water as a stop bath for film. I've not use acid stop for film in 20+ years. There is no reason to. A good wash in running water, or 4-5 water exchanges after development is sufficient.

PicklesFrog · Apr 4, 2024

pentaxuser said:
Here's a test to try. Pour some more diluted citric acid into the tank with the lid on, agitate it for about 30 secs maximum then pour it out. Place your nose over the hole in the lid. Is the smell the same? If it is then that suggests it is the citric acid you smell but if it is different then it might be koraks' explanation that describes what you smelled

I did this and it smelled like the solution i started with (a "something" smell, not not smelling but not the smell i smelt after the developer step.

koraks said:
This has a particular smell to it and it's quite strong/pungent. Perhaps you're mistaking this for the smell of citric acid.

Yeah it was bad. luckily I just got back from work and my room smells fine after a full day (more or less) of the window opened. Throat is settling down and my nose still kinda burns/hurts when i take a deep breath. we live and learn.

I talked to my chemistry professor and they said the sulfur dioxide is what more than likely happened based on the reaction i had explained to her.

chuckroast · Apr 4, 2024

koraks said:
Oh, LOL! Right, see how that goes and if perhaps the acetic acid smell is tolerable. In a weak dilution, it may not be too bad. Smells a bit like a salad dressing that way!

Yeah, sort of a prickly sensation. Some people are (much) more sensitive to this than others. I do get that prickly sensation the moment I smell it, but generally no after-effects. But it's an irritating gas for sure.

In point of fact, the ordinary formulations for working stop bath is to make a nominal 28% acetic acid by mixing Glacial Acetic Acid in a ratio of 3+8 water. This works out to be 27.27%.

One then mixes the 27.27% in a ratio of 6+128 to make working strength stop bath. This thus ends up being around 1.22% acetic acid in solution.

Ordinary white cooking vinegar is about 5% acetic acid - chemically identical to the stuff above. When mixed in a ratio of 1+3 with water, we get 1.25% acetic acid in solution - near enough the same thing. (It's also rather inexpensive.)

So, if acetic acid isn't easily found, white cooking vinegar works just fine.

PicklesFrog · Apr 4, 2024

chuckroast said:
+100 on using water as a stop bath for film. I've not use acid stop for film in 20+ years. There is no reason to. A good wash in running water, or 4-5 water exchanges after development is sufficient.

The only thing I am worried about is that the Darkroom Cookbook and the compact photo lab index says the same thing (its literally the same thing):

A white scum of calcium sulfite may occur on films processed in high-sulfite, low-alkalinity developers. This scum is soluble in acid stop baths and in fresh acid fixing baths,

is this an issue for people that don't use an acid stop bath with d-23?

chuckroast · Apr 5, 2024

PicklesFrog said:
The only thing I am worried about is that the Darkroom Cookbook and the compact photo lab index says the same thing (its literally the same thing):

is this an issue for people that don't use an acid stop bath with d-23?

I use D-23 with running water for 30 seconds as a stop bath when I open tank process. When I use daylight tanks, my stop regiment is four fill-empty cycles before going to fix.

I suspect any issues I might have seen get handled by the constant water exchange, but I've never really looked into it deeply.

By the way, this includes using D-23 at higher-than-usual dilutions which are lower-than-usual alkalinity..

koraks · Apr 5, 2024

chuckroast said:
I suspect any issues I might have seen get handled by the constant water exchange

I'd expect so, yes.

Do use some kind of rinse, at least, though. The other day I was feeling adventurous and skipped a stop altogether, going from developer (not D23 but Pyrocat) to C41 fix. I was treated to the most massive case of dichroic fog I've ever seen.

chuckroast · Apr 5, 2024

koraks said:
I'd expect so, yes.

Do use some kind of rinse, at least, though. The other day I was feeling adventurous and skipped a stop altogether, going from developer (not D23 but Pyrocat) to C41 fix. I was treated to the most massive case of dichroic fog I've ever seen.

Yes, the "stop" step is intended to literally "stop" the development, thereby providing consistency of process, and reducing developer carryover into the fix.

I'm curious, why C-41 fix rather than one of the more conventional monochrome fixers?

koraks · Apr 5, 2024

chuckroast said:
I'm curious, why C-41 fix rather than one of the more conventional monochrome fixers?

C41 fix works for everything (unless you're being stupid, as I was) and I don't see the point in stocking several types of fixer.

chuckroast · Apr 5, 2024

koraks said:
C41 fix works for everything (unless you're being stupid, as I was) and I don't see the point in stocking several types of fixer.

Do you use it for monochrome silver paper as well?

koraks · Apr 5, 2024

chuckroast said:
Do you use it for monochrome silver paper as well?

Sure. Everything. Salt prints, Van Dykes etc., too.

Saganich · Apr 5, 2024

PicklesFrog said:
The only thing I am worried about is that the Darkroom Cookbook and the compact photo lab index says the same thing (its literally the same thing):

is this an issue for people that don't use an acid stop bath with d-23?

Never has an issue with white scum on film using stock D23...can't make any claims for dilutions...which would cause less alkalinity anyway. Stock D23 isn't high alk imho. My fresh stock with distilled water measures pH 7.8 and increases slightly with replenishment to just over pH 8.

koraks · Apr 5, 2024

Saganich said:
which would cause less alkalinity anyway. Stock D23 isn't high alk imho.

Yeah, but I think that's the point. Take this quote from the Cookbook:

A white scum of calcium sulfite may occur on films processed in high-sulfite, low-alkalinity developers.

There was a recent incident with someone reporting problems under such conditions. A couple of weeks ago IIRC; the details elude me at the moment. It might have been D23 in fact. I could imagine something similar happening with XTOL, which works at a similar pH and is also (very) high in sulfite.

chuckroast · Apr 5, 2024

koraks said:
Yeah, but I think that's the point. Take this quote from the Cookbook:

There was a recent incident with someone reporting problems under such conditions. A couple of weeks ago IIRC; the details elude me at the moment. It might have been D23 in fact. I could imagine something similar happening with XTOL, which works at a similar pH and is also (very) high in sulfite.

I've used D-23 at 1+3 and at 1+9 with lye added, with water stop in every case. I've had no issues.

Milpool · Apr 5, 2024

Generally calcium precipitation will not be an issue with commercially prepared developers which contain chelating compounds to deal with water quality. Of course using distilled water when scratch-mixing photographic processing solutions (not just developers) is advisable, but an acid stop is never a bad idea.

chuckroast · Apr 5, 2024

Milpool said:
Generally calcium precipitation will not be an issue with commercially prepared developers which contain chelating compounds to deal with water quality. Of course using distilled water when scratch-mixing photographic processing solutions (not just developers) is advisable, but an acid stop is never a bad idea.

That might be why I've never had an issue with a water stop. I mix all chems with distilled water.

pentaxuser · Apr 5, 2024

chuckroast said:
That might be why I've never had an issue with a water stop. I mix all chems with distilled water.

I use tap water for all my rinses including the final wetting agent stage and also never have had an issue My water is so hard that I have to treat the kettle to a limescale remover every few weeks

pentaxuser

Pioneer · Apr 5, 2024

chuckroast said:
+100 on using water as a stop bath for film. I've not use acid stop for film in 20+ years. There is no reason to. A good wash in running water, or 4-5 water exchanges after development is sufficient.

To each his own I guess. I do occasionally use a fresh water stop when it is called for but 4 or 5 exchanges of water when you are working with a septic system is a bit excessive and also unnecessarily time consuming. Especially when 30 seconds in a dilute vinegar stop addresses the issue nicely and stops development quickly.

I am not trying to pick on anyone and it does work, though not very quickly. So everyone should make their own decisions on whether the process fits their needs. Since you do a lot of stand development I would guess that one, your developer is pretty well exhausted at the end of your process so stopping development quickly is not an issue, and second, the additional time required for four or five water exchanges is not really important. Finally running additional fresh water down the drain doesn't cause additional problems when you are working on a sewer system, as most folks do nowdays.

It is nice to have options.

snusmumriken · Apr 5, 2024

koraks said:
Yeah, but I think that's the point. Take this quote from the Cookbook:

There was a recent incident with someone reporting problems under such conditions. A couple of weeks ago IIRC; the details elude me at the moment. It might have been D23 in fact. I could imagine something similar happening with XTOL, which works at a similar pH and is also (very) high in sulfite.

So wouldn't that be a problem with D-76 too?

pentaxuser · Apr 5, 2024

Pioneer said:
I am not trying to pick on anyone and it does work, though not very quickly. Finally running additional fresh water down the drain doesn't cause additional problems when you are working on a sewer system, as most folks do nowdays.

It is nice to have options.

Initially when I started to process film I used an acid stop bath as that was the convention and in the beginning convention was best. I am unsure when I switched to several fills and dumps of water but it has to be at least 2-3 years later

I certainly cannot recall suddenly or even slowly noticing that my negatives were in any way different nor did that seem to translate into differences in my prints. There may well have been differences which are/were measurable by a densitometer but none I could see that were enough to cause me to change back to an acid stop bath

I can imagine that with very short development times such as those getting close to times that none of the film and developer makes recommend it might just be that the immediate action of an acid stop bath does make a difference but given that the dumping of developer and immediate flush with water must dilute the developer's action overwhelmingly and less than 10 secs later the second fill and dump dilutes what remains of the highly diluted developer from the action of the first flush and dump then I have difficulty understanding of how the very slightly slower water stop bath really make a difference to the negative

Now I think about what might have caused me to re-think the need for an acid bath I have a vague feeling that I read an article that actually tested what the dilution rate was the remnants of the developer after the fill water fill and flush If I recall correctly it reduced the action of the developer to an almost infinitesimally low level

On a practical level, if the development time is say 8-10 or 12 mins then how much time does the water bath take to stop the developer's action in comparison with acid stop?Unless we know that this is, say, more than 15 secs so at least half way or all the way through the second fill and dump of water then unless there is strong evidence to the effect that changing development time by 15 secs in say 10 mins development time makes a real difference then it really shouldn't have a deleterious effect, should it?

I am unclear as to what problems say 3 fills and dumps of a water stop bath can make to a sewer system? Yes it might increase you water bill but by a very small level even if you develop an awful lot of films so other than that what are these problems?

Of course it's each person to his or her own method and that's fine but on a strictly practical level I do have difficulty seeing the real benefits of an acid bath for film

Thanks

pentaxuser

What About Bob · Apr 5, 2024

I use Sprint block stop bath. It has a pleasant vanilla scent that may make it tolerable for some people. It has indicator in it too.

I have noticed a white streaky scum that forms when a tiny bit of D23 leaks from the tank while inverting or when some of the liquid gets outside of the container. When I see any streaking I just dab the area with a slightly damp paper towel. My negatives haven't been affected by any of this. I am not sure what causes this since I am using distilled water when mixing all of my chemistry.

Milpool · Apr 5, 2024

The Sprint product is actually an ideal stop bath (ie buffered acetic acid-sodium acetate). Not that we should make too much of stop baths but worth noting all the same.

What About Bob said:
I use Sprint block stop bath. It has a pleasant vanilla scent that may make it tolerable for some people.

chuckroast · Apr 5, 2024

Pioneer said:
To each his own I guess. I do occasionally use a fresh water stop when it is called for but 4 or 5 exchanges of water when you are working with a septic system is a bit excessive and also unnecessarily time consuming. Especially when 30 seconds in a dilute vinegar stop addresses the issue nicely and stops development quickly.

I am not trying to pick on anyone and it does work, though not very quickly. So everyone should make their own decisions on whether the process fits their needs. Since you do a lot of stand development I would guess that one, your developer is pretty well exhausted at the end of your process so stopping development quickly is not an issue, and second, the additional time required for four or five water exchanges is not really important. Finally running additional fresh water down the drain doesn't cause additional problems when you are working on a sewer system, as most folks do nowdays.

It is nice to have options.

I do some semistand/EMA development, but I also develop with conventional agitation.

The most important thing about process is consistency. So, if there continues to be some slight development during the water exchange process, I want that to be done every single time. That's why I either use continuous running water for sheet films and 4 water exchanges for daylight tanks - to get the same results every time (for a given format).

My general paranoia about pinholing (however unlikely) caused me to make this switch many decades ago, and I've observed no issues with any developer, using any agitation discipline.

As you say, there are many ways to work and I think the consistency rather than a single rigid process is considerably more important.

(Also, it's one less chemical I have to mix

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