Stop Bath.. How important?

[nworth]

Out of habit, I use two water rinses after the developer for film and a two percent acetic acid stop bath for paper. This has worked fine for more years than I can remember. Logically, it may be backward. After all, film development is what needs to be really stopped at a definite point - paper essentially gets developed to completion. An acid stop bath may give a little insurance against stain on the paper, and it may protect the (very slightly) acid fixer, but not much. In any case, it seems to work. This is not an area of great criticality unless something doesn't work. If that happens, you need to start again with the conventional methods.

[Michel Hardy-Vallée]

But not as many use no stop what so ever.
I don't bother with it at all. Develop then fix,
film and paper. I use all chemistry one-shot so
am not concerned with a build up of developer
in the fixer. Also ph shift is no issue. An acid
stop is for the purpose of maintaining the
acidity of an acid fix.

The short rinse in an acid stop does not wash out
the developer any quicker than plain water but the
acidity of the fixer keeps the accumulated developer
in the fix from being active.

The accumulation of developer is an issue with those
who use an alkaline fixer where-in the accumulated
developer is always active. Dan

Yep, that's another scenario that make sense.

I think with the acidic/alkaline stop/wash questions, what matters is not whether a stop bath is inherently good or bad, but whether one's workflow makes sense or not.

[fschifano]

Well, I'll tell you. I have used an acid stop bath, mixed at the recommended strength, on films for many years. A while back, I experimented with using a water wash as a stop bath just to see if there was any appreciable difference in the negatives. The comparison films were shot under similar, but not identical, conditions, leaving some wiggle room there to argue my results.

Bottom line is that I really couldn't see a whole lot of difference in the negatives, and even less when it came to the resulting prints. The differences could easily be chalked up to the fact that my exposures were not made under identical conditions, small development time deviations, and maybe even the phase of the moon. What I did find though is that my fixing bath (acid fixer) did not last nearly as long without having used the acid stop.

The only complaint I have with indicating stop baths is the yellow dye that gets carried over to the fixer. I eliminate the problem by washing the film with a couple of changes of water between the stop and fixer. Everything works out fine.

And what's the story about the smell? I hear a lot of complaints about that, but I've got to wonder what else is going on. Stop bath, if used at the recommended strength, really doesn't smell all that much. True, there is that vinegar odor, but it should not be so strong as to be irritating to most people. If the smell is really bothersome, then perhaps something else is wrong and needs to be corrected. Maybe the stop bath is mixed up too strongly, or more ventilation in the work area is needed. For those who are extraordinarily sensitive to acetic acid, a good substitute is citric acid with no odor.

[Ole]

There is yet another way, which I've used with good results a few times:

No stop, and no fix!

Instead of pouring the developer out and the fixer in, I dump about a tablespoon of ammonium thiosulfate dissolved in a little water straight into the spent developer.

I figured that with a very dilute developer (like Rodinal at 1:100) the developer would be almost completely dead at the end of the developing, and what was left would be mostly some sodium sulfite and a little alkali. Since that's what an alkaline fixer contains in addition to thiosulfate, I decided it was worth a try.

Well - it works. In fact it works just great - with some developers, and not so great with some others. Rodinal is fine, Ilfotec HC not so fine.

[Alan9940]

PE,

You are probably right about the pinholes and the cause-n-effect as it relates to using an acid stop bath. To be honest, I never bothered tracking down why I was getting the pinholes because I stopped using that particular film. Overall, I would say that I started using a water stop mostly due to my use of PMK for many years followed, more recently, by Pyrocat HD; and the fact that the dilution I was using was so weak it seemed pointless to continue using the acid.

As with most things photographic I guess it comes down to: whatever works for you.

Thanks, though, for the clarification that the pinholes were probably not caused by the acid stop bath. Should I ever experience this issue, again, I'll look elsewhere.

[Vaughn]

I have read arguments for using stop bath, such as:

"I am strongly opposed to the use of a water rinse as a "short stop" bath. There are some problems related to colloidal sulfur, and staining etc. I know some of you will decry my position saying that it never happened to me, however, it may be happening as we speak and you won't know about it for months or years to come."

"To begin with, acetic acid conditions and toughens gelatin without hardening it."

These statements were made by H. Lynn Jones in another forum. I quote them not in their support, but to get some sort of feedback as to their accuracy. Mr. Jones is a long time instructor and has worked in the manufacture of lenses, etc. He is knowledgable and worth listening to.

One last quote from the same discussion...

"I agree with Lynn, water may not show the signs colloidal sulfur, and staining on prints straight away however in time and especially on large prints problems can arise. Just ask any photo librarian or gallery curator and they will let you know exactly how much more longevity prints get when stop bath or acetic acid have been used."

I have never heard such opinions mentioned here in APUG, so I am wondering what PE and others think about the the effect on longivity that using water instead of stop bath might have on film and paper.

Vaughn

[Roger Hicks]

I am told by someone whose experience and knowledge I trust (though I have never tried to verify it experimentally) that if you photograph an even grey tone, and process without a stop bath, it is far more difficult to maintain evenness. He knew this because it was a 'party trick' at his college -- it may have been the London College of Printing, but I have forgotten -- that was used to persuade people that stop baths are not necessarily irrelevant.

I have never bothered to try to verify it because it is never visible in 'real world' negatives. For films, both he and I will either go straight from dev to fix, or use VERY weakly acidulated water -- a dash of glacial acetic acid in water, used one-shot -- between the two. I've not used 'full strength' stop bath in decades, not from fear of pinholes, but because I find my ways easier.

Paper is another matter. There, I use standard-strength stop bath, made up from glacial acetic (or currently, Tetenal 60% acetic, because it's easier to get) because the chemicals sit in the Nova tank and are re-used to within distant sight of exhaustion, unlike film processing. Strong acetic is so cheap that I just don't worry about the tiny added cost, or about chucking it out before it's exhausted.

[Roger Hicks]

"To begin with, acetic acid conditions and toughens gelatin without hardening it."

Dear Vaughn,

I'm not sure what 'conditions' might mean, nor, in the context of gelatine, can I see how you can 'toughen' without 'hardening': both, surely, can be achieved only by water reduction or breaking cross-linkages. My knowledge of the chemistry of gelatine is however lamentably poor: I have only the weakest understanding of the nature of isoelectric points, for example, and that, only when I am reading about the subject in a well-written text. Like you, I'd be interested to hear PE's comments on this.

Cheers,

Roger

[Vaughn]

Thanks for your replies, Roger.

The only thing I understand about the chemistry of gelatin is that it is very difficult to understand, LOL! An interesting substance!

Vaughn

[Photo Engineer]

Gelatin swell is minimized at a pH of about 4.5, which is where the acid stop bath (acetic acid) would be. Therefore, the tendancy for gelatin to scratch or abrade is minimized.

The tendancy to form stains and to form a dichroic image are minimized by a stop bath. In fact, a stop is beneficial in removing any amine containing developing agent from film or paper. In particular, metol is of note. Metol is slow to remove in water.

Papers develop much more rapidly than films. Therefore a stop is much more effective in getting a uniform image in paper than film in some cases. This is to be noted in the posts above. It takes 10 minutes or so to develop films, and some take longer depending on developer. Paper is moving at 10X that rate and must be stopped in a shorter and more effective fashion for just that reason.

PE