Hey Bill,
Glad to have you join the discussion, and indeed, knowing your love for glass I figured it was just a matter of time!
So over the weekend I've had a new idea for this one. My friend is a jewelry maker, and I asked her about casting glass and she started telling me about
enamel.
Basically it's powdered glass with pigment that you fire and it will fuse to various metals. There is even a technique called
plique-à-jour, which means 'letting in daylight' and is like stained glass in that it's designed to be viewed with transmitted light.
She also has a small kiln which excites me...
So anyways, I was thinking back to the original idea; using a plaster mold from a swelled carbon matrix (there are many, many precedents for this kinda thing, a lot of photoengraving techniques use it...). In the mold you could pour the very fine enamel powder into it, probably with a fairly high degree of resolution, use a very flat blade of sorts to scrape the top off, leaving enamel only in the valleys and in proportion to the image density, and finally fire it and allow the enamel to flow & fuse, hopefully not to the plaster, but just to itself.
This would leave you with a very fragile image in enamel, and you'd have to "lift" it out of the mold and ultimately combine it with the 2 other layers if you're doing full color. I wonder if this would work...
Bill, maybe after we have the 3 layers, they could be put onto a sheet of glass and fired one last time to fuse them all together into a true stained glass photograph?
Let me know if you come across some suitable CMY colors in enamel. I've done a little looking and it seems like a good magenta might be the hardest, but I'm sure it's really hard to tell from online color swatches. Also, how did your experiments in Pt/Pd/Au end up?