Ferri and dilution to use for bleach back and lith redevlopment.

Discussion in 'B&W: Film, Paper, Chemistry' started by Andrew Moxom, Jan 7, 2008.

  1. Andrew Moxom

    Andrew Moxom Member

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    I am going to attempt to use ferri bleach on some of my images to bleach back the image and then continue development in lith developer. I will be using PF ferri powder and wanted to know how much to use to make a solution. How much powder per litre of water to mix? Also, how long does it last? Is it something that can be reused, or is it really just a one shot deal? I have an accurate scale I can use to weigh the powder.
     
  2. blaze-on

    blaze-on Member

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    You'll have to add Potassium Bromide too. In Anchell's cookbook there's a simple solution, but I haven't got it with me.
    Probbly a site search here will yield results.
     
  3. ann

    ann Subscriber

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    you can also use the bleach from a sepia toning kit. just weaken it greatly.

    a standard bleach formula is:
    • Potassium ferricyanide 10 grams
    • Potassium bromide 5 grams
    • Water to make 1000 ml


    you can also use a variety of other bleach types, each will give a different color shift to the specific paper type your using


    The bleach can be re used many times, of course the times get slower, but that isn't always a bad thing.

    we do this type of psduo liths in my classes all the time, people love it
     
  4. Andrew Moxom

    Andrew Moxom Member

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    But for print redevelopment I would not need to add the halide (Bromide) correct? I want to be able to strip away the super coating, and then redevelop a print in room/day light and then refix after infectinous devleopement is complete. Adding bromide I thought would make the bleach permanent??

    Workflow would be over expose print, dev in regular developer, stop, and fix. Wash, hypo clear, wash again. Then Ferri bleach back, wash, and redevelop in lith developer. At snatch point, Stop, fix and wash, hypoclear, selenium tone, hypoclear, wash, dry.
     
  5. Ole

    Ole Moderator Staff Member Moderator

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    NO, add the bromide.

    Or chloride, if you like, or a mixture. That makes a "rehalogenising bleach" - so you're just changing the silver back to undeveloped halides. Without bromide you get potassium silver ferri-cyanate, which is not quite the same as silver halide.

    BTW - why the hypoclear between fix and toning? selenium toner contains thiosulfate, so the hypoclear is redundant.
     
  6. Rich Ullsmith

    Rich Ullsmith Subscriber

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    Andrew, I am not familiar with the PF stuff you have, but yes it must have a halide in order to redevelop. I usually use equal amounts KBr and K ferricyanide in the concentrations Ann said, basically ten grams each per liter for starters. You don't necessarily need to over-expose your print to bleach and develop. And not all papers will give a lith effect on redeveloping, so don't be discouraged. Warm tone RC papers are fun to play with, and the processing/times are much shorter.
     
  7. Andrew Moxom

    Andrew Moxom Member

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    Thanks Blaze on, Ann, Ole, and Rich.. I will look into the Bromide as well. Thanks again for the assistance.