>I cannot remember the title of the article or the author, or even the
>date, but I believe it was about 5 or 6 years ago that _Scientific
>American_ published an article on this very topic. There are actually
>artists who are working with this irridescence and also the variety of
>colors that are formed.
Are you talking about the article on "chromoskaedasic (sp?)
pseudosolarisation"? An artist outlined in Scientific American used
stabilization process chemistry (thiocyanates as I recall) to paint on
unexposed photographic papers. Unfortunately, I do not have the reference
handy, but I also recall this technique was adapted by a photographer who
published some articles in one of the popular darkroom magazines around 5
years ago.
The chemistry affects the size of silver grains within the emulsion and adds
various colors. Treatment of an exposed and developed print causes a partial
reversal of the tones and imparts a color shift in portions of the image. The
result is a colored, chemically-derived Sabbatier effect on the print.
I may still have a copy of the article at work and will post the reference if
I can find it.
Joe