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  1. #1

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    is Potassium Alum same as Potassium Chrome Alum?

    I need to make a hardening fixer for using with liquid light and was thinking of Kodak F6. Formula says to use "potassium alum". I've got an old kodak glass bottle labeled "potassium chrome alum" [purple crystals inside] and was wondering if anyone knew if this was the same as the "potassium alum" in the Kodak F6 formula?

    Alternatively, does anyone know a good non-rapid hardening fixer to use with liquid light? Thanks.

  2. #2
    Ian Grant's Avatar
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    No quite different, both are used as hardeners but Potassium Chrome Alum needs extra care the Chromium can cause issues with broken skin and also breaks down in fixers. It' can be used as a hardening stopbath. Kodak published a formula. Don't add it to a fixer though.

    You can add a fesw drops of Chrome alum solution to the Liquid light prior to coating they used to suggest this anyway.

    Potassium alum is easy to get hold of btry a chemists (dru store).

    Ian

  3. #3

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    No.
    Potassium alum is potassium aluminium sulfate KAl(SO4)2 while potassium chrome alum is chromium potassium sulfate KCr(SO4)2.
    With a non hardened emulsion you need a glutaraldehyde hardener, such as Rollei RBM5.

  4. #4
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    You can use the Potassium Chrome Alum in the following way....

    First, make up your fixer without the hardener. Then, make up a 10% Potassium Chrome Alum.

    Here is the modified process sequence.

    Develop
    Stop or rinse in running water
    If you use a stop, then rinse in running water
    Chrome Alum 10% for 5 minutes at 20C
    rinse 5 min at 20C
    fix in your non-hardening fixer
    wash
    dry

    This will harden most anything.

    An alternate with LL is as follows:

    Harden 10% Chrome Alum 5 mins
    wash 5 mins
    develop
    stop or rinse
    fix in non hardening fixer

    There are several more prehardeners for LL such as:

    Formalin 3&% 10 ml
    Sodium Sulfite 50 - 100 g/l
    Sodium Carbonate 25 - 50 g/l
    pH to 10.0

    Have fun.

    PE



 

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