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Well, I'm not sure that the mordant worked imagewise or if the mordant was applied imagewise to an image formed by another method. You can always find something like this, but IMHO the description is not entirely clear. If you look at the classics, the mordant was "everywhere" and an image was applied to the mordant and stuck imagewise to a uniform layer of mordant.
PE
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Thanks everyone for the replies. I suspected it was complicated. I'm obviously in over my head on this one, but thought it was an interesting idea. I think for now though this will have to go on my list of "experiments to try maybe at some point".
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Michael, I've used the dye coupler route a lot in the past mainly for hand colouring images, but I've used it to intensify negatives as well.
With negatoves it's rather like using XP1/XP2 film the only difference is you add the coupler to the colour developer rather than it being in the film and you can chose the colour or mix of colours.
It has an adavantage in that a film can be passed through the cycle a few times, dev in a normal B&W developer & fix washn well then bleach in a rehalogenating bleach wasg dev in C41 ith the coupler(s), wash, then repeat the bleach/dev again. This technique was once very common with astro photography for colour films and called looping.
So back to your initial question yes you can add a dye colour, proprtional to the exposure very easily.
Ian
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Interesting thanks for the input Ian. I think part of my nervousness with stuff like this has to do with the whole bleach-redevelop thing, which I've not explored in any detail, nor ever tried, other than with paper just to play around with some toners. But since I don't tone my prints in anything other than selenium, I never went any further, and on the film side I've never needed that kind of process, so I'd really have to do alot of reading on this subject before trying it.
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Vanadium toning will turn your negs green. Sadly it isn't permanent.
Worship the Mystery Chicken who died on the spit with relish. Ohhhmmmm.
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interesting thread
thanks people
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 Originally Posted by Photo Engineer
Well, I'm not sure that the mordant worked imagewise or if the mordant was applied imagewise to an image formed by another method. You can always find something like this, but IMHO the description is not entirely clear. If you look at the classics, the mordant was "everywhere" and an image was applied to the mordant and stuck imagewise to a uniform layer of mordant.
PE
It's true, I didn't pick the best passage to quote. But, the mordant or toning action definitely worked image-wise; the whole chapter is devoted to this idea. I guess the Brewster Color Process (formerly unbeknownst to me) worked on this/these principle(s).
Here's the opening paragraph from Friedman, which explains it better:
A clear piece of film, when bathed in solutions of basic dyes, can be washed clear of all coloring matter. But if the film be given a previous bath in chrome or potassium alum, it will no longer be possible to wash the dye out. The chromium or aluminum ions unite with the gelatin to form stable salts or complexes. These can unite with the dye to form insoluble or "laked" pigments. Many other substances beside alumed gelatin, have this property of mordanting dyes. Since it is so easy to transform the silver of a photographic image into a variety of other insoluble salts, it is apparent that a further reaction with dye becomes possible, provided a corect choice has been made with regard to the conversion. This is the fundamental principle underlying the dye-toning processes. Slightly more general in scope, since they are not limited by the previous formation of a silver image, are the mordant processes. Here the mordant images are formed either from silver or by exposure of a non-mordanting light-sensitive system, which forms mordants or products that can be converted into mordants, by the action of light
I'm far from an expert on the details, but I do think it's possible to do what Michael wants to do. The formulas in the chapter are not particularly complicated or exotic.
Anyways, a fun thread and an interesting proposition.
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Yes, you are correct. The metal mordant is formed imagewise by light or by reaction by a silver metal image.
Sorry, but I was not thinking clearly enough on this subject. Thanks for the catch Chris.
PE
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Thanks Ron,
You've probably forgotten more than most of us have ever learned! And I mean that in a good way. 
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I've forgotten more than I ever knew.
PE
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