Citric and acetic acid as stop (bath)

[pkr1979]

Hi all,

Im curious to know about experiences and how one can use both citric acid and acetic acid as a stop bath when developing black and white negative film

My acetic acid is 100 %, how should I dilute this?

And my citric acid is powder - how should I mix this?

Cheers
Peter

[Alan9940]

To make a 28% stock solution of Acetic Acid, mix 3 parts glacial acetic acid to 8 parts distilled water. I mix up ~16 ozs at a time: 4.5 oz acid to 12 oz distilled water. Probably doesn't need to be said, but make sure to add the acid to the water. I use a citric acid stop for paper development because I don't like the smell of acetic acid in the darkroom. The old Kodak SB-8 formula calls for 15g citric acid per liter of water, but I go more dilute by mixing a heaping teaspoon per liter.

[Two23]

I was using vinegar in my stop bath for film but didn't see any difference from just using water. My developer is HC110.


Kent in SD

[Pere Casals]

For film, I'd recommend to you use just plain water, you dump water each time (two times if you want) so stop bath does not accumulate chem and also no chem is transported to the fixer. Long ago fixers were usually acidic, but today fixers are usually alkaline or neutral, so it may make no sense transporting acid to the fixer.

________

"The fumes which emanate from acetic acid stop baths are perhaps the single greatest health hazard in the darkroom"

Be careful, mix glacial acetic bath outdoors if possible: 1% to 2% working solution.

________


Citric Stop bath: 15gr of acid for 1L


________

Get The Darkroom Cookbook, you'll find it useful, cheap if used


________

For paper I use acid stop bath, for film plain water, YMMV

[koraks]

My acetic acid is 100 %, how should I dilute this?

With great care!! That stuff is nasty. Seriously, I use unparfumated cleaning vinegar because I wouldn't want to have glacial acetic acid around the house, and I'm pretty used to having nasty stuff in my darkroom. Cleaning vinegar is generally something like 7-8%; typical dilution for a stop bath would be 1.5-2%, but if used one stop (which I'd recommend) for film, much less is already quite effective. Try something like 0.5%; it won't have much buffering capacity, but with one shot use, this isn't a problem.

Citric acid I generally use for paper and I just wing it in terms of concentration. Something like a tablespoon to one or two liters of water gets things going. You notice easily enough when the stop bath has worn out because the paper's emulsion doesn't get that rubbery/resisting feel anymore within a few seconds which it typically does with a fresh stop bath. Add some more citric acid or discard and mix fresh. The one-table spoon/1-liter stop bath generally lasts me easily through a printing session.

[Jeroen]

...typical dilution for a stop bath would be 1.5-2%,
That's the right dilution. But I prefer indicator stop bath, it's cheap and last a looooooong time. I discard it when it turns purple.

[pkr1979]

Thanks for getting back to me good folks.

The developing Ive been doing at home is E6 and black and white reversal... I tought black and white regular negative film developing consisted of the steps: developing - stop - fix. But as I understand some of you guys, to develop black and white negative film you only need to develop and then fix?

Is this developer dependant? I use PQ Universal with Ilford Ortho Plus (I might use either Ilfotec dd-x or id-11 with HP5+ and Pan F+).

[jim_jm]

You want to have a "stop" bath step between the developer and fixer, whether it's a acid stop or plain water is up to you. The goal is to remove the developer from the surface of the film/paper as quickly as possible to halt the developer action. This will also eliminate any residual developer from being transferred to your fixer, which will definitely shorten it's capacity. Many say that acid stop is more effective at neutralizing the developer and it's impact on your fixer, others see no difference in using just plain water.
A bottle of Kodak Indicator Stop or Ilfostop lasts a very long time, and I also depend on the color change to know when to dump and mix a new batch.

[koraks]

I've never experienced any difference between a plain water stop and an acetic stop in b&w. With color negative I'd suggest always using an acetic acid stop bath. With b&w, some form of stop or rinse before fixing ensures that no additional development or fogging occurs during fixing.

[Doremus Scudder]

... I thought black and white regular negative film developing consisted of the steps: developing - stop - fix. But as I understand some of you guys, to develop black and white negative film you only need to develop and then fix?

Is this developer dependent? I use PQ Universal with Ilford Ortho Plus (I might use either Ilfotec dd-x or id-11 with HP5+ and Pan F+).

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. The usual dilutions range from 40-48ml of 28% acetic acid stock to one liter of water. Kodak recommends one part Indicator Stop (28% acetic acid with an indicator dye added) to 63 parts water. This makes 2 oz. per gallon, or one oz per half gallon or one-half oz per quart.

One note about citric acid-stop baths: working solutions don't keep well, since they easily support the growth of bacterial slime. I use my citric-acid stops one-session only.

Best,

Doremus

[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.