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  1. #31
    gainer's Avatar
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    Pyro is one of the oldest developing agents. There should be some negatives remaining from those days. My grandfather's glass plate negatives made before 1905 could have been done in pyro or MQ, I don't know which. A few show signs of incomplete washing. A problem is that the pyro stain was not wanted by most, and enough sulfite was used to prevent most of the staining. The standard developer at the time of Hardy & Perrin's Principles of Optics, 1932, contained 70 grams sodium sulfite, 17 grams sodium bisulfite, 20 grams pyrogallic acid, to make a liter of solution A and 75 grams sodium carbonate, 1 gram potassium bromide to make 1 liter of solution B. Equal parts of A and B were used for the working solution. I doubt there is much stain when one develops in that solution. Hardy & Perrin state that the color coefficient of a pyro developer depends on the amount of restrainer and do not mention sulfite. The color coefficient is the ratio of gamma measured photographically to that measured visually, and ranges from about 1.3 with the usual amount of restrainer to as much as 3 with no restrainer. We might get some idea of stain fading from any negative known to have been developed in pyro simply by printing it on graded paper and VC paper, but it would be a very rough idea.

    It's interesting that pyro was the sole developing agent.
    Gadget Gainer

  2. #32
    Ole
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    Gainer, one of my old books states that "an acid stop bath should be used to remove the unsightly stain from the pyrogallol".

    Another popular developer around the (previous) turn of the century was the iron sulfate developer, which gave bluish-black tones to the negative.
    -- Ole Tjugen, Luddite Elitist
    Norway

  3. #33
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    The worst that could happen is uneven fading. If the dye faded evenly , it could be restored by bleaching and redeveloping in a staining developer.
    Gadget Gainer

  4. #34

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    [QUOTES=BobNewYork;568267]
    "The Darkroom Cookbook and/or The Film Developing
    Cookbook indicate that sodium thio. may not adequately
    fix modern emulsions so ammonium thio is the way to go."

    Sodium thiosulfate is the fixer. The ammonium is the
    speed; Rapid. Given some more time over the rapid
    the slower sodium form will thoroughly fix.

    "Also, over-fixing in sodium thio will start to bleach
    the image - ammonium doesn't have these problems."

    Just the opposite of at least the conventional wisdom.
    I wonder though which has the most potential to bleach,
    an acid or alkaline fixer?

    "The value of short wash times without the additional HCA
    bath cannot be over-estimated either!"

    Little time spent washing is in my mind to be preferred
    to short wash times. Dan

  5. #35
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    Quote Originally Posted by dancqu View Post
    [QUOTES=BobNewYork;568267]
    "The Darkroom Cookbook and/or The Film Developing
    Cookbook indicate that sodium thio. may not adequately
    fix modern emulsions so ammonium thio is the way to go."

    Sodium thiosulfate is the fixer. The ammonium is the
    speed; Rapid. Given some more time over the rapid
    the slower sodium form will thoroughly fix.

    "Also, over-fixing in sodium thio will start to bleach
    the image - ammonium doesn't have these problems."

    Just the opposite of at least the conventional wisdom.
    I wonder though which has the most potential to bleach,
    an acid or alkaline fixer?

    "The value of short wash times without the additional HCA
    bath cannot be over-estimated either!"

    Little time spent washing is in my mind to be preferred
    to short wash times. Dan

    I'm confusing about Sodium Thio and Ammonium Thio also the Alkaline and Acid Fixer. I can't find the Ammonium Thio in Thailand so I use the TF2 (alkaline fixer) which is based on Sodium Thio. Is it ok to wash the Pyrocat?

  6. #36
    Ole
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    There is some doubt whether modern film emulsions (meaning T-grain and Delta) will be fully fixed with a sodium thiosulfate fixer since these emulsions contain more silver iodide than most "older" emulsions. silver iodide is a lot more difficult to dissolve than either silver bromide or silver chloride, the two other components in the silver halide crystals in the emulsion.

    The ammonium in ammonium thiosulfate has an accelerating effect on the dissolution of silver halides, as the ammonium ions also form soluble silver complexes.

    So it doesn't matter which developer you use, only which film you use.

    If you want / feel you need the extra "zap" of ammonium thiosulfate, you can add ammonium chloride to the fixer. Or for that matter - look up "OF-1" in the recipe section here. That's an alkaline rapid fix based on sodium thiosulfate and ammonium chloride.
    -- Ole Tjugen, Luddite Elitist
    Norway

  7. #37
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    Thanks Ole, I'll try the OF-1. Can it fix the FB paper?

  8. #38
    Ole
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    Quote Originally Posted by TN98 View Post
    Thanks Ole, I'll try the OF-1. Can it fix the FB paper?
    So far, it has fixed everything i've tried. There's nothing "magic" about it, just a little applied chemistry.

    It works. It fixes film and paper, even T-max and Bergger Art Contact (both contain silver iodide, AFAIK).

    It can be used full strength or diluted 1+1, although I prefer full strength and would only recommend full strength for film.
    -- Ole Tjugen, Luddite Elitist
    Norway

  9. #39

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    Quote Originally Posted by Ole View Post
    There is some doubt whether modern film emulsions
    (meaning T-grain and Delta) will be fully fixed with a
    sodium thiosulfate fixer since these emulsions contain
    more silver iodide than most "older" emulsions. silver
    iodide is a lot more difficult to dissolve than either
    silver bromide or silver chloride, the two other
    components in the silver halide crystals
    in the emulsion.

    The ammonium in ammonium thiosulfate has an
    accelerating effect on the dissolution of silver halides,
    as the ammonium ions also form soluble silver complexes.
    The thiosulfate ion is one of only two ions which will dissolve
    ANY salt of silver. The ammonium ion will complex with silver
    where many of the not so very insoluble salts are involved.
    The ammonium ions affinity for silver in the presence of
    iodide is near nill.

    Verification of the above are the much longer fix times
    and much reduced capacities of Rapid fixer when iodide
    is present. Thiosulfate carries the load due to it's much
    greater affinity for silver. Where iodide is not involved
    an ammonium fixer can be RAPID. Dan

  10. #40
    Cor
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    PE,

    I quote Richard Knoppow on this (perhaps you know him, he seems quite knowledgeable, but I do not know his source, I could ask.):

    "The stain however, is not a dye, but rather, a pigment
    related to Humic Acid, the substance which colors wood
    brown. Unlike dye it is very permanent, more so than the
    silver."


    Best,

    Cor

    Quote Originally Posted by Photo Engineer View Post
    But, an interesting observation has grabbed my attention. All of the 'staining' processes are doing is creat a pseudo dye in the coating around the silver grain. This dye blurs the grain, but can also detract from sharpness. But, my point is this, or rather my question is this. What is the stability of this pseudo dye? What will happen to 'stained' negatives over time. Does the pyro induced coloration fade? It certainly fades or is bleached in acid sulfite fixes. Is it not fair to assume that the stain/tint/dye is less stable than the silver and will change over time?

    I just wonder if anyone has run that type of test. Because, if the dye is not stable, then all of this discussion about staining developers is moot.

    PE

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