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  1. #1

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    Alkaline Bleach-Fix with Ferric Ammonium EDTA?

    Hi,

    I'm curious if anyone happens to know whether it's possible to formulate an alkaline bleach-fix using Ferric Ammonium EDTA as the primary bleaching agent.

    Cheers...

  2. #2
    Rudeofus's Avatar
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    What's the pH you are aiming for?
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #3

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    Originally, I was aiming for 7.5-8.5; but now I'm just curious if it's possible at any alkalinity.

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    Sorry, I guess 'alkalinity' isn't the best word to use there. Let's just say any pH above 7, but ideally something that isn't caustic.

    I've done a few test before doing simple substitutions from a formula that originally specified acetic acid, but obviously there wasn't any activity to the solution.

    I would also be interested if it is possible to formulate a rehalogenating bleach using any EDTA salt in an alkaline environment.

  5. #5
    Rudeofus's Avatar
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    Watch out for nasty Ammonia smell at pH 8 ...

    Since you started this thread in the b&w forum: what are you trying to bleach?
    Trying to be the best of whatever I am, even if what I am is no good.

  6. #6

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    Why do you feel that the blix should be alkaline? Cemically there would be no advantage in doing this. There is the possibility of the iron III hyydrolysing and coming out of solution when the pH goes above 7.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  7. #7

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    The film I'm bleaching in KODAK 7366 Tri-X Reversal (i.e. Black and White 16mm motion picture film) processed as reversal. The film has not, however been processed in the conventional manner. Instead of...

    First Developer
    Bleach (Dichromate/Sulfuric)
    Clear
    Second Developer
    Fix

    I decided to process the footage as such:

    Developer
    In-direct Toner
    Bleach (rehalogenating)
    Fix

    ...a reversal by toner sort-of-speak.

    The process worked fine with a conventional ferricyanide bleach, but care had to be exercised so as to avoid having the bleach destroy the positive image. This is because ferricyanide does a poor job differentiating between the toned image and the untoned image (and for similar reasons, ferricyanide isn't used in color chemistry, which eventually led to the use of ferric ammonium EDTA...and so forth)

    Therefore, I began using a ferric ammonium EDTA based Bleach-Fix's and ended up with this process:

    First Dev
    Indirect Toner
    Blix

    For the most part, I'm satisfied with the process, but for "less-than-scientific reasons," I was interested in keeping the entire process alkaline; specifically, the alkalinity of sea-water...

  8. #8

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    Right, that's what I was thinking... Is that the case with all EDTA salts? Do they only remain stable in acids?

  9. #9

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    The hydrolysis has nothing to do with the EDTA it is a problem with iron salts. Metal bleachs, iron, manganese, chromium, and copper will not work in alkaline solution. The correcponding metal hydrated oxides will precipitate out of solution.
    Last edited by Gerald C Koch; 03-25-2013 at 06:36 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  10. #10

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    Is there a particular reason to use an indirect toner?
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

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