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  1. #1

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    Adding potassium ferracyananide to paper developer

    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. #2
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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

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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. #4

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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. #5

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    I'm cringing

    Quote Originally Posted by Rich Ullsmith View Post
    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!
    As I think of the paper I've thrown away, not knowing this trick!

    Dang!

  6. #6
    Ole
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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?
    -- Ole Tjugen, Luddite Elitist
    Norway

  7. #7
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    Quote Originally Posted by analogfotog View Post
    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?
    Used for contrast control, knocks the shadows down to a grade -2 or so:

    http://unblinkingeye.com/Articles/La...agebleach.html
    DARKROOM AUTOMATION
    f-Stop Timers - Enlarging Meters
    http://www.darkroomautomation.com/da-main.htm

  8. #8

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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. #9

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    Quote Originally Posted by Photo Engineer View Post
    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
    Thanks for the input, PE and everybody who contributed. How much Bromide and/or Benzotriazole should be added, for a start?

  10. #10
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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

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