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  1. #41
    wildbill's Avatar
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    Quote Originally Posted by wildbill View Post
    Here's an informative essay from Joseph Holmes' site I read recently:
    http://www.josephholmes.com/processes.html
    scroll down to permanence.
    I'm curious, anyone have a response to this?

  2. #42

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    Quote Originally Posted by railwayman3 View Post
    Just looking at a list of the relative permanence of artists watercolors, the most permanent seem to be those using simple mineral- and metal-compound-based pigments, while the least permanent are those with natural or sythetic organic pigments, particular the more delicate colors.

    All modern photo processes use complex organic dyes, and the choice of dyes to use is particularly restricted to those which are of the exact colors needed, which can be formed during processing and the components of which are sufficiently stable, economical, not-too-poisonous, etc, etc., to be incorporated into emulsions and processing chemicals.
    This pretty much says it all, especially that the dyes used in film must be formed during processing. This is probably the most important factor here, as it pretty much rules out the use of highly stable, metal-based dyes (like, say, iron oxide for reds). This is also a BIG reason why inkjet prints have the potential to be MUCH more long-lasting than traditional prints: dyes are simply sprayed on, and are therefore NOT restricted to colorless compounds that take on color after processing.

    Speaking of dyes, does anyone know the exact nature of the dyes that are used when processing Kodachrome?

  3. #43
    Photo Engineer's Avatar
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    Matt;

    Please read my previous post on this. To summarize, Lead and Cadmium were used and preferred for pigment dyes, and things can be done to stabilze organics.

    As for the Kodachrome dyes, yes, I know what they are and you can see them as well. They are in a patent by R. Bent and R. Mowrey.

    PE

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