Adding potassium ferracyananide to paper developer

Discussion in 'B&W: Film, Paper, Chemistry' started by analogfotog, Apr 4, 2008.

  1. analogfotog

    analogfotog Member

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    No, this isn't a joke, and it's too late for April Fool's Day (I did love the post about Kodak making Panatomic-X available in ULF, though).

    A friend of mine has a bunch of AGFA Portriga paper which was quite old, and apparently heat damaged. He asked me what he could do, and I suggested adding some sodium- or potassium bromide to the paper developer (Dektol, diluted 1:3). He had neither of those chemicals, but he did have some potassium ferracyananide, of which he added a pinch, to 2 litres of developer.

    The results aren't perfect, but they're not bad; the blacks are a bit weak, and the contrast low, even on grade 3 Portriga, but the whites are clean. I suggested that he try diluting the developer 1:1 or 1:2 to restore the blacks, and try a half-pinch (only in a pinch, of course!), instead of a full pinch, of the potassium ferracyananide.

    I have never heard of adding potassium ferracyananide to developer; has anybody ever done this, or have any knowledge of it? Could somebody explain why this seems to work?
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    Potassium Ferricyanide reacts instantly with Metol, HQ and Sulfite thereby destroying a portion of the developer. Fog appears to go down, but contrst also goes down and blacks will be weak. Wait..... Thats what he saw. Ok, so that is what you expect to see.

    And, you may never be able to reformulate to get back where you want to. Low fog and good dmax. OTOH, Bromide and Benzotriazole work by not harming the developer, just by reducing speed and fog, which is the right way of doing things.

    PE
     
  3. Rich Ullsmith

    Rich Ullsmith Subscriber

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    If he has a bunch of this paper, then it's time to pick up some lith developer! This paper responds very well to a dilute lith developer, and the fog isn't an issue. With old papers, even if they appear hopelessly fogged (so long as it's due to age and storage conditions and not light exposure) you can still get the whites of the paper base with lith process. Whatever your friend decides to do with it, tell him not to chuck it in the garbage!
     
  4. PVia

    PVia Member

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    With old paper like this and using normal silver gelatin process (not lith), would a short ferri bath restore whites suppressed from age fog?
     
  5. Paul Verizzo

    Paul Verizzo Member

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    I'm cringing

    As I think of the paper I've thrown away, not knowing this trick!

    Dang!
     
  6. Ole

    Ole Moderator Staff Member Moderator

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    If potassium bromide works by shifting the solubility equation, wouldn't a lot of sodium chloride do the same thing? It could be worth trying about 20 g of table salt instead of 1 g potassium bromide?
     
  7. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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  8. Jordan

    Jordan Member

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    I'm with Photo Engineer. You're adding an oxidizing agent (ferricyanide) to reducing agents (metol, sulfite, hydroquinone, etc.) and they'll destroy each other until one of them is used up. All you're doing is reducing the strength of your developer.
     
  9. analogfotog

    analogfotog Member

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    Thanks for the input, PE and everybody who contributed. How much Bromide and/or Benzotriazole should be added, for a start?
     
  10. Photo Engineer

    Photo Engineer Subscriber

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    The amount of bromide or benzotriazole (BTAZ) varies with the level of fog and the type of paper.

    I woud start at 1 - 2 g/l of bromide or 10 - 20 mg/l of BTAZ in methyl alcohol.

    The idea of using the paper for lith printing is a good one. Adding sodium chloride can have a bad effect. It is not a good antifoggant.

    PE
     
  11. dancqu

    dancqu Member

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    Bleach Before Developing

    A post exposure pre-development rinse of the paper
    in an extremely dilute K. Ferricyanide solution is a
    method of contrast control. Dan