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  1. #1

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    Alum Hardener formulas for use BEFORE developing on soft emulsions?

    Hi,
    Are there any film hardener formulas based on non volatile not very toxic reagents (alums, aluminium chloride etc) that can be used BEFORE the developing step to harden films with softer emulsions (Efke etc).

    The film developing cookbook gives a glutaraldehyde formula but I would like to avoid aldehydes in a home darkroom if possible.

    I would like to put the hardening step at the very beginning, if possible, but I can't find any potassium or chrome alum based formulas for the purpose.

    Thanks,
    Santanu
    Last edited by chakra; 10-19-2011 at 11:37 PM. Click to view previous post history.

  2. #2
    Ian Grant's Avatar
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    You could convert your developewr to a tropical developer by adding Sodium Sulphate, alternately use a hardening stop bath which is Chrome alum solution.

    I use EFKE films with no hardener and no issues, using a Pyro heveloper helps as it tans and hardens the film during development. Before EFKE imroved their emulsion hardening I used to add a few drops of Formaldehyde to the developer to aid hardening & reduce swelling (that was back in the 1970's).

    Ian

  3. #3
    Rick A's Avatar
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    My choice as well, Pyrocat-HD tans the emulsion and makes it even more resistant to damage than it already is.
    Rick A
    Argentum aevum

  4. #4

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    With a reel development even Efke films are not a real problem. Formalin 37% works OK in an Alkaline environment. So adding a very small volume to the developer works very well. Often Rodinal is used for Efke films and this contains Sodium Hydroxide in a high level.

    Greetz,

    Роберт
    My favorite store: http://www.fotohuisrovo.nl

  5. #5
    Vaughn's Avatar
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    I believe the alum hardeners are fairly slow acting, thus may not be what you are looking for.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  6. #6
    Ian Grant's Avatar
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    Quote Originally Posted by Vaughn View Post
    I believe the alum hardeners are fairly slow acting, thus may not be what you are looking for.
    They also need acidic conditions to work and that's not a great idea before a developer.

    Ian

  7. #7

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    @Ian - Thanks for the detailed response describing your experience with the film. Did you see any evidence of fog with the formaldehyde you added. I may give this a shot with glutaraldehyde. The cookbook mentions that you can add glutaraldehyde to the developer itself but I was worried it might fog the film.

    @ Rick and Ian - Yeah ... I've been wondering about Pyro developers for this purpose but I've never used them. I like rodinal with Efke films a lot ... but I should try pyro without stressing about toxicity.

    @Vaughn - How many minutes do you think alum hardeners would need if used as a presoak? I don't know the chemistry but since most fixers are done in less than 10 minutes I imagine a 10 minute presoak would give decent hardening. What I am worried about is the prehardener interfering with the developer.

    Thanks for your responses.

  8. #8

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    I was worried about the acidic conditions. What if I give a good rinse in water? But the presoak times would be getting up there.

  9. #9
    Vaughn's Avatar
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    For Alums, I believe it would be in hours, not minutes, thus not practical for film as a pre-hardener. My experience with potassium alum has been with hardening the gelatin of carbon prints.
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  10. #10

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    For making a 0,1% Formaline solution you need 2,7ml 37% Formaldehyde in 1 ltr. water/developer. So for a 500ml roll film tank add 1,35ml.

    Роберт
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