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  1. #1

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    Kodak indicator stop bath dilution

    I believe the pH of the standard working solution (fresh) is somewhere between 2 and 3. If one were to mix it at half strength (say 8ml/l instead of 16ml/l), does that increase the pH significantly? I think total acidity would decrease, but not sure how much the pH would increase. Actually, is a half-strength mix of Kodak stop bath even still an effective stop bath? Working on some new experiments with PMK and I can't find all my old notes. Hutchings recommended the "ideal" stop bath pH of 4.5 in his book, but frankly I'm not sure how much of all that is still valid.

    Further, Wimberley always recommended a standard stop bath be used with his various WD2 developers even though they use a carbonate alkali. Which reminds me of another question - is it really necessary to avoid acid stop baths with carbonate-driven developers? Or does it really depend on the pH of the particular developer?

  2. #2
    cliveh's Avatar
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    If you are not a pyro dev user like me, then a standard indicator acidic stop bath is fine. I like to make mine to a dilution that is not harmful to dip your fingers in.

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

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    I can't answer any of those but I haven't used stop bath (just plain water) in 10 years. I use pmk, tmax, sometimes rodinal. Hell, I don't use it when printing either.
    www.vinnywalsh.com

    I know what I want but I just don't know how to go about gettin' it.-Hendrix

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    JPD
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    I use about 10 ml 24% acetic acid for a liter stop bath for film, less than recommended, and never had any problems.

    A plain water stop bath when using a developer with carbonate seems like a good suggestion. I don't remember which developer I used, but it contained Sodium Carbonate, and then an acid stop bath. The millions of small bubbles in the emulsion ruined the negatives...
    J. Patric Dahlén

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    Leigh B's Avatar
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    I use Kodak Indicator SB per the instructions. No problems in over 55 years of doing so, with my bare hands.

    Some folks are more sensitive to chemicals than others.

    Quote Originally Posted by Michael R 1974 View Post
    Hutchings recommended the "ideal" stop bath pH of 4.5 in his book...
    People write books to sell books. Repeating the common wisdom does not sell books.

    Ergo, anything you read must be taken with two or more grains of salt.

    Given the number of different developers available, I don't know how one could even define the 'ideal' stop bath.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

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    Quote Originally Posted by JPD View Post
    I use about 10 ml 24% acetic acid for a liter stop bath for film, less than recommended, and never had any problems.
    The commercial white vinegar is only 5% concentrated acetic acid. Where do you find the 24% solution?

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    Quote Originally Posted by Leigh B View Post
    I use Kodak Indicator SB per the instructions. No problems in over 55 years of doing so, with my bare hands.

    Some folks are more sensitive to chemicals than others.


    People write books to sell books. Repeating the common wisdom does not sell books.

    Ergo, anything you read must be taken with two or more grains of salt.

    Given the number of different developers available, I don't know how one could even define the 'ideal' stop bath.

    - Leigh
    I mostly agree. I have always used Kodak SB per instructions except with developers using a carbonate alkali. With those developers I've followed the conventional wisdom and used a water stop. The exception to that rule has been Pyro, where some people say a stop bath is desirable to halt general dye formation. An exception to this, of course, is PMK which uses a Metaborate alkali, and Hutchings's book has never been entirely clear nor convincing to me. Some people say imagewise stain continues to form post-development. Others say it is just general stain that forms post-development. It could depend on the formula, but really?

    So I set out to test some of these things.

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    JPD
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    Quote Originally Posted by Photo-gear View Post
    The commercial white vinegar is only 5% concentrated acetic acid. Where do you find the 24% solution?
    "Absolut Ren Ättika 24%" and "Ättikssprit 12%" is available in any grocery store here in Sweden. They are the standard white vinegars here. You can probably find something similar in North America, try a pharmacy, hardware store or a paint shop.
    J. Patric Dahlén

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    Leigh B's Avatar
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    Quote Originally Posted by Photo-gear View Post
    The commercial white vinegar is only 5% concentrated acetic acid. Where do you find the 24% solution?
    Food-grade glacial acetic acid is readily available at about $12 for 950ml here in the States.

    Dilute 1+3 with distilled water if you want 25%.

    Of course you can substitute citric acid, but peeling all those lemons and oranges is a royal PITA.

    - Leigh
    Last edited by Leigh B; 08-05-2012 at 07:25 PM. Click to view previous post history.
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

  10. #10
    Leigh B's Avatar
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    Quote Originally Posted by Michael R 1974 View Post
    With those developers I've followed the conventional wisdom and used a water stop.
    Not wanting to start an argument, but water is not stop bath, it's water.

    Any developer in the emulsion continues to do its job until fixation is complete and there's nothing left to develop.

    - Leigh
    “Wise men talk because they have something to say; fools, because they have to say something.” - Plato

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