Citric and acetic acid as stop (bath)

[Alan9940]

Note: Some people use a water bath in place of an acid stop bath. There is still a "stop-bath" step in the workflow; the negative does not go directly from the developer to the fix.

The above advice on dilutions are right on. Keep in mind, that if you mix a 28% acetic acid stock solution, as Alan suggests, you'll need to further dilute it to make your working solution.

Thanks, Doremus, I forgot to mention that the 28% stock requires further dilution. FWIW, my use of acid stop or plain water generally is tied to what film developer I'm using on what film. For example, if I'm using a fast acting developer like HC-110(B) I'll tend to use an acid stop because the overall development time is short and that's a vigorous formula. When developing any film in any pyro formula, I always use plain water. For paper, it's citric acid and I mix fresh after about 10 8x10 sheets or equivalent.

[Fred L]

I use a water stop for all films. Agitation is important and will usually do two changes. For fiber prints, I use citric acid, one tablespoon per litre. The citric acid I use is food grade, and one I use at a community darkroom for outreach programs as well, since it's virtually odour free. Also gets dumped after every print session.

[pkr1979]

Thanks for all this feedbcak guys. Its very helpfull and I apreciate this a lot :-)

[Drew Wiley]

I use glacial acetic acid at around 1/2 %, mixing just enough per daily session. I never re-use anything. It's nasty and appropriate precautions should be followed, including a fume hood. With safer 28% Indicator Stop Bath, I just dilute it to a light pee color, which amounts to about the same concentration.

[adelorenzo]

Kodak's SB-8 formula for citric acid stop bath is 15g/L. I keep a scoop in my big tub of citric acid powder that gives me approximately that much and just mix one-shot as needed. Throw a scoop in and add water. Takes about 10 seconds.

[Joe O'Hara]

Agree with Doremus, citric acid should be discarded at the end of the session (but it is good for quite a few sheets of film or paper).

Aside from being odorless, it is very cheap if you buy it in big bags from canning or craft suppliers on the internet. There's no sense in
buying it from photo chemical suppliers as though it were a specialty item. If "food grade" citric acid is good enough to put in your canned
veggies it's plenty good enough for stop bath!

[koraks]

I generally keep my citric acid stop bath around for maximum ca 10 days. It's easy to tell when it goes bad as it will have strands of slime floating around in it. Discarding after one session is of course perfectly fine an prevents any problems.