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Thread: Citric and acetic acid as stop (bath)

  1. #1

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    Citric and acetic acid as stop (bath)

    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

  2. #2

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    Re: Citric and acetic acid as stop (bath)

    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.

  3. #3
    Foamer
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    Re: Citric and acetic acid as stop (bath)

    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
    Qui sedes ad dexteram Patris,
    miserere nobis.

  4. #4

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    Re: Citric and acetic acid as stop (bath)

    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

  5. #5

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    Re: Citric and acetic acid as stop (bath)

    Quote Originally Posted by pkr1979 View Post
    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.

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    Re: Citric and acetic acid as stop (bath)

    Quote Originally Posted by koraks View Post
    ...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.

  7. #7

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    Re: Citric and acetic acid as stop (bath)

    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+).

  8. #8
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    Re: Citric and acetic acid as stop (bath)

    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.

  9. #9

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    Re: Citric and acetic acid as stop (bath)

    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.

  10. #10

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    Re: Citric and acetic acid as stop (bath)

    Quote Originally Posted by pkr1979 View Post
    ... 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

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