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  1. #1
    David Lyga's Avatar
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    restraining and reducing: the role of bromide

    Two seemingly simple questions I have:

    First: What is the precise role of bromide in Farmer's Reducer?

    Second: With regard to restrainers: Is there ever a circumstance whereby potassium bromide is preferable to benzatriozole?

    - David Lyga

  2. #2
    Ian Grant's Avatar
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    First bromide isn't used in Farmers reducer, although it won't hurt if it's there/

    Second Benzoriazole produces cold tones with prints and so shouldn't be added to warm tone developers.

    Ian

  3. #3
    David Lyga's Avatar
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    Ian, the formula for Farmer's reducer contains bromide. I do not use it but it is there. Am I incorrect? (Thank you for the warm tone exception.) - David Lyga

  4. #4

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    Quote Originally Posted by David Lyga View Post
    First: What is the precise role of bromide in Farmer's Reducer?
    I think you mean re-halogenating bleaches. Potassium bromide is used so that when the silver is oxidized it is converted to silver halide again. Such a bleach may be used in connection with an intensifier.

    Ag0 - electron --> Ag+ + Br- --> AgBr
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  5. #5
    Ian Grant's Avatar
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    No true, Farmers reducer is a two part reducer mixed just before use.

    Rarmers Reducer

    Part A
    Sodium Thiosulphate 40g
    water to 1 litre

    Part B
    Potassium Ferricyanide 19g
    Water to 250ml

    To use 1 part B + 4 parts A

    Make up to 32 parts with water

    ie 10ml B + 40ml A + 270ml Water = 320ml working solution.
    It has a very short life


    A very lazy way is to use a rehalogenating bleach used for toning with some fixer, however this is faster working and not as controllable and you shouldn't use a Rapid fixer.

    Ian

  6. #6
    Rudeofus's Avatar
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    Quote Originally Posted by David Lyga View Post
    Second: With regard to restrainers: Is there ever a circumstance whereby potassium bromide is preferable to benzatriozole?
    Yes, if cost and trivial availability mean anything to you
    Trying to be the best of whatever I am, even if what I am is no good.

  7. #7
    David Lyga's Avatar
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    Not true, Ian, for print reducer. This 'unblinking eye' site (upper right of page) shows the reducer for prints: http://unblinkingeye.com/Articles/De.../formulas.html

    But, Ian, the negative reducer is as you state: no bromide. I wonder why the difference? - David Lyga

    And Rudeofus: 'trivial availability' has to be conquered but once in one's lifetime: a bit of benzotriazole goes far and can be kept permanently in powder form if airtight. - David Lyga

  8. #8
    Ian Grant's Avatar
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    Quote Originally Posted by David Lyga View Post
    Not true, Ian, for print reducer. This 'unblinking eye' site (upper right of page) shows the reducer for prints: http://unblinkingeye.com/Articles/De.../formulas.html

    But, Ian, the negative reducer is as you state: no bromide. I wonder why the difference? - David Lyga

    And Rudeofus: 'trivial availability' has to be conquered but once in one's lifetime: a bit of benzotriazole goes far and can be kept permanently in powder form if airtight. - David Lyga
    Farmer's Reducer has never had Bromide in the official formula, and it's been sold by many companies. Agfa Ansco (GAF) 310 (which I listed above), Kodak R-4a and R-4b, and Ilford IR-1 are all named as Farmer's Reducer and essentially just slight variations in terms of concentration but only use Ferricyanide and Sodium Thiosulphate.

    So there's a mistake on that website.

    Ian

  9. #9
    Jim Noel's Avatar
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    I agree with Ian. I have been at this business of analog photography fro more than 70 years, and I have never seen the formula shown in "Unblinking Eye". Farmer's Reducer is a simple two solution formula mixed just prior to use.

    Jim
    [FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]

  10. #10
    cliveh's Avatar
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    David, are you confusing Farmer's reducer with sepia tone bleach?

    “The contemplation of things as they are, without error or confusion, without substitution or imposture, is in itself a nobler thing than a whole harvest of invention”

    Francis Bacon

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