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  1. #1

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    Yet another C41 Ferricyanide bleach question ...

    I've had a go at C41 development this weekend using the recipe in this thread http://www.apug.org/forums/forum40/5...developer.html

    The results were quite good enough for the odd roll of colour I do shoot (I doubt I'll be dunking anything other than "Poundland" AgfaVista200 or ColorPlus in it). I got a bit of a magenta cast, but frankly I've had worse back from the minilab, and as it'll only ever be scanned it's of no great concern.

    I used a simple ferricyanide/bromide bleach step (I followed PE's recommendations about using an acid stop, sulfite clearing bath and wash before bleaching in this), as I had both components to hand anyway.

    Despite searching, I can't find answers to the following questions:

    1, What is the most appropriate formula for a ferricyanide bleach for this purpose ? (I used what I had already made up for 2-pass lith experiments , at 10g+10g/litre; and it worked, so empirically that's fine, but it would be nice to have a more definitive answer)

    2, can the bleach be reused a few times ? (for this first go, I dumped it after use)

    thanks in advance.

  2. #2
    Rudeofus's Avatar
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    There is no such thing as a correct formula for a C41 Ferricyanide bleach since C41 film is not rated for this bleaching agent. Based on that you should rephrase your question as "is there a Ferricyanide bleach recipe that has been successfully used with color processes?", and this question I would answer by pointing to the Watkins Factor page. Note that this page does not provide a correct formula for E6, but some people were reportedly happy with the results and the bleach at least didn't eat their film.
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  3. #3

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    Thank you Rudeofus.

    Having done some research before asking the question, I did phrase the question carefully, which is why I asked for an appropriate formula for this purpose rather than a correct formula.

  4. #4
    Mike Wilde's Avatar
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    I use 80g ferri and 20g bromide per litre. Mix up 2 l at a time. Use one l for working, one l for the replenisher. I replenish 45mL per film (80 sq in).

    Bleach for 2:30 at 38C. Intermittent agitation about every 30 seconds with this mix.

    Might work fine at a lower replenisher rate at the beginning or may work woth a lower rate overall. I have not tested lower rates.
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  5. #5

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    thank you, Mike

  6. #6

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    The closest thing to a recommended bleach you can probably find is Kodak SR29, used as an alternative bleach in the ECN-2 motion picture process. Motion picture films and still films are not the same, but they are probably sufficiently similar for this to work properly.

    Kodak Bleach SR-29
    Alternative bleach for color negative motion picture process ECN-2.

    Water (32C) 900 ml
    Potassium ferricyanide (anh) 40 g
    Sodium bromide (anh) 25 g
    Water to make 1 l

    pH@25C=6.5

    Bleach time is 3 minutes at 38C.

    Replenisher (SR-29R)

    Water (32C) 900 ml
    Potassium ferricyanide (anh) 55 g
    Sodium bromide (anh) 35 g
    Water to make 1 l

    pH@25C=8.0
    Replenishment rate is 200 ml per 100 feet of film (or about 10 ml per roll).


    30 g of potassium bromide is roughly equivalent to 25 g of sodium bromide (1.21 g of KBr equivalent to 1.05 g NaBr).

  7. #7

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    thank you too, nworth.



 

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