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Thread: Utocolor

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    Utocolor

    An interesting process from before the 1st World War was UTOCOLOR. Dr. J.H. Smith of Zurich, Switzerland introduced Uto color paper as long ago as 1904. It worked on the principle (which Dr. Smith called) of the Bleach Out law."A coloured body sensitive to light will only be affected by the light it absorbs, but not by the light of it's own colour". This means, as regards to the process: that Red light will destroy a Cyan dye and leave red dye, and so forth with other colours. This was by no means an original theory. Grothus had written about a theory not unlike this as long ago as 1819.
    The paper was used to make prints from the very few colour transparencies of that time, notably Autochrome. There was no dev. or fix, after exposure to the trans. by contact printing, the paper was "stabilised" (!) in a Uto bath. I suppose today's equivelant would be a reversal colour print paper. Although there were improvements, (1906, 1911) I beleive the process died out before the 1st World War. But Utocolor marked the beginning of the "Silver Dye Bleach" process. The principal name associated with the process is Dr. Bela Gasper. "Gaspercolor Opaque" became "Cilchrome" then "Cibachrome" .

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    The problem was that the bleaching process never stopped, and so the prints gradually faded away.

    Besides which, the exposure times to get the original print were so long and at such high intensity the original transparency could fade and it took hours in full sunlight.

    The dye bleach process relies on silver halide to form the oringinal image, but again, the process involves long exposures due to the dye blocking the incoming light and it also involves rather coarse grain so we see no practical in-camera applications of dye bleach.

    PE

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    Seems like an interesting process, though.

    What light-sensitive material was used in the UTOCOLOR paper? Or was it just dyes??

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    Utocolor used dyes bleached by light itself. A cyan dye was bleached by red light as an example. Stopping the process was virtually impossible and therefore it was slow photographically, but then the image just continued to fade when hung out for display.

    Of course, when you get down to it all dyes are bleached by light and that is why all dyes fade. Rate is just very slow in current products. It is slow enough to allow display in open sunlight and still last for nearly 100 years. This, of course, would be a very slow photographic material requiring about a 100 year exposure for starters. Then you could hang the print out for anohter 100 years for display.

    PE

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    I've always been interested in Utocolor. Are there any examples anywhere? Of course, it would be faded. But surely there's been one that was stored well and is in reasonable condition.
    If you are the big tree, we are the small axe

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    Your assignment, should you decide to accept it, is to find one!

    Good luck!

    PE

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    holmburgers's Avatar
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    And so my journey begins...
    If you are the big tree, we are the small axe

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    http://books.google.com/books?id=xBz...ocolor&f=false

    Here's a really good write up of Utocolor, written at the time of its introduction.
    If you are the big tree, we are the small axe

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    There is a complete description in "History of Color Photography" by Friedman.

    PE

  10. #10

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    Quote Originally Posted by holmburgers View Post
    http://books.google.com/books?id=xBz...ocolor&f=false

    Here's a really good write up of Utocolor, written at the time of its introduction.
    As usual, google sees my presence overseas punishiable
    by exposure to their "snippet views".

    Thanks Goo Goo!

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