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  1. #91

    Join Date
    Sep 2002
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    Willamette Valley, Oregon
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    Quote Originally Posted by Kirk Keyes
    Perhaps the high density of the lith image
    makes the stain not noticable.
    Just what I was thinking possible. Many years ago I did
    process camera work and half tone processing. I was not
    looking for color then but on reflection do not recall any.
    Those little dots are small and/or compressed and all
    very dense.

    The little lith printing I've done shows the dense portions
    to be black, warm at best, while any less dense areas shade
    from light tans to very dark browns; at least with my
    homebrew lith. Dan

  2. #92

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    Sep 2002
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    [QUOTE=sanking]
    "For whatever it is worth."

    I can only wonder what is going on with that hydroquinone.
    That 2 grams/liter is also a Lith developer sulfite maximum.
    Reconcile, if you will, HQ's oxidation products giving lith
    development and at the same time those oxidation
    products being involved in tanning gelatin.


    I've given that above some additional thought. On reflection,
    when working with my lith surprise brew, I saw that the
    image tanned brown as it emerged. After several minutes of
    slow increase in density a rather fast increase took place.

    Hydroquinone initiates the reduction of the silver halides and
    the semiquinone is produced. The semiquinone is consumed
    by the gelatin, that being tanned. Hydroquinone MAY be
    regenerated at that time. Quinone though, necessary
    for infectious development, is NOT produced.

    After most of the tanning has been done the semiquinone is
    free to oxidize to the quinone and infectious development
    takes off. All that with low sulfite levels.

    But what if sulfite levels are high? Nothing happens; perhaps
    a faint image. Interesting. By that I'd conclude that more
    than a very little sulfite will maintain a regenerated
    hydroquinone.

    Likely the level of sulfite mentioned, 2 grams per liter, may
    vary some and one still expect a tanned, lithed print. Dan

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