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  1. #11
    Ian Grant's Avatar
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    Pyrocatechin or Pyrogallol were used in commercial MQ developers by Ilford and also Kodak to extend the life as well in D&P developers.

    Ian

    Adding: In a 1941 BJP article on the modern uses of Pyro developers there's a section on the MQ developers like D75 and D75b which include Pyro. The Pyro acts as an oxygen absorber someting that had been know bu then for some time according to the article.
    Last edited by Ian Grant; 05-24-2012 at 03:27 PM. Click to view previous post history. Reason: adding much later

  2. #12
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    Quote Originally Posted by Nicholas Lindan View Post
    I wonder what a combination of ascorbate and Glycin would do? I feel an experiment coming on...
    Of all the dev ingredients I could imagine for a long shelf life and long tray life developer, ascorbic acid is about the last one I would pick ... even if you pick a suitable sequestering agent (i.e. not Calgon) to capture all the iron, aerial oxidation must still be reckoned with.
    Trying to be the best of whatever I am, even if what I am is no good.

  3. #13

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    Quote Originally Posted by Keith Tapscott. View Post
    Gordon Hutchins chose metaborate for his PMK formula, so I guess he went against that advice.

    The extra ingredients in packaged developers don't worry me, I was just curious to know more about them. Thanks Gerald.
    "... the ability of borate ions to form stable molecular complexes with compounds containing hydroxyl groups on adjacent carbon atoms. Thus catechol and pyrogallol or certain of their derivatives should not be used in developers based on borates." Mason, p 34. The developing capability of catechol is almost completely eliminated and that of pyrogallol seriously reduced. Of course this does not apply to the metol in the PMK fgformula.
    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

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