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  1. #21
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    As Patrick says, Sodium Chloride in high enough concentration can reduce swell. In fact, a number of chemicals can do this, but the Sodium Chloride has solvent effects which can overwhelm the swell effect and this is why Sulfates are chosen.

    A mixture of Sulfate and Bisulfate in either an acid or basic solution before development, and which contains formalin or succinaldehyde or glutaraldehyde can be a very effective hardener. The basic solution is much more effective.

    Prehardener

    Water 800 ml
    Formalin 37% 10 ml
    Na2SO4 50 g
    Na2CO3 50 g
    pH to 10.0 with NaOH or H2SO4
    Water to 1 L

    Use for 1 - 3 mins, then wash for 5' before development. This will harden a soft film product for use in solutions up to 100F.

    And Patrick, Merry Christmas. I do wish we could meet in person. There is so much we could teach each other.

    PE

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    not to mention how much you could teach me - last night I got the book "Caveman Chemistry"

    ....I haven't even learned to make by fire by rubbing sticks together yet

  3. #23
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    I make emulsions by rubbing two silver halide molecules together in the presence of gelatin.

    Next time you come to the George Eastman House, give me a call or join one of our GEH lunches. There will be up to 6 or more of us there at one time. We talk about Darkroom Experiments!

    PE

  4. #24
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    Quote Originally Posted by DarkroomExperimente View Post
    not to mention how much you could teach me - last night I got the book "Caveman Chemistry"

    ....I haven't even learned to make by fire by rubbing sticks together yet
    It's not easy. It's somewhat easier if you use the bow method.

    "Caveman Chemistry" is a good book, and fun to read even if you know everything that's in it.
    Gadget Gainer

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