Is there a substitute

Discussion in 'Color: Film, Paper, and Chemistry' started by mrred, May 29, 2014.

  1. mrred

    mrred Subscriber

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    I have been using this bleach for a while, and ditching the blix from the c-41 powder kits.

    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).


    I just ran out of the sodium bromide an am wondering if there is a substitute for it?
     
  2. Rudeofus

    Rudeofus Subscriber

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    I have no idea why they use Sodium Bromide in that bleach if Potassium Bromide is so much more easy to get. To get the same amount of mols you'd have to use 15% more KBr, but honestly: it won't make much difference.

    PS: You do know that Ferricyanide bleach is not recommended for C41 or E6, yes?
     
  3. mrred

    mrred Subscriber

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    Yes, but I have it and it works well. This is more than I can say for the BLIX.

    I'm not sure why they don't recommended it, but after a year or so, I don't see anything wrong.

    I actually use Potassium Bromide. Jacks pages suggest a 1.16 factor.
     
  4. Gerald C Koch

    Gerald C Koch Member

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    Kodak typically used sodium salts in their formulas. The sodium salts may have been cheaper.
     
  5. mrred

    mrred Subscriber

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    Gerry, what does the bromide do in this function? It has never been explained to me.

    I ran out because I had only stocked this chem based on making developers. 100 grams goes fast when making bleach..... :smile:
     
  6. Rudeofus

    Rudeofus Subscriber

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    If you oxidize the Silver with the Ferricyanide, you need to give it some anion to be happy, and the Bromide serves that purpose. Together with oxidized Silver it will form Silver Bromide, an insoluble salt that will be removed by the fixer.
     
  7. mrred

    mrred Subscriber

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    Thanks