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I had an opportunity to talk to an expert in Autochromes today. He said that they had restored the original machine that made Autochromes. It was found in France at a location near the Lumiere home and was painstakingly restored.
As of now, several years later, they have been unable to get it to make one single piece of the color mask from starch grains. In fact, in all of the tries around the world in the last half century, he knows of no one who has been able to accomplish this critical and difficult step.
PE
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Hmm, sounds as if there was a secret pretreatment done to the starch grains that was missed. Perhaps hydrolysing the starch just before or after application to the glass? Interesting info PE.
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Hm ... I'm having exacty the same problem. I've dyes corn starch (easy to work with for now), and suspended them in various substances (so far honey works well, but it never dries, so off to another substance), though it sort of works. However, it is incredibly difficult to get even distribution of a monolayer.
I'm going ot try gelatine again, though I have not been able to find a dye that doesn't come off slightly in water (the grains remain colored, but diffuse some dye into the aqueous environment). I'll try washing them a few times before suspension in gelatine.
In some research, I did discover that the grains were separated by size by a process that involved floating them in water - this may be something...
Someone at <http://www.bway.net/~jscruggs/specific.html> seems to ahve figured it out, and has produced a filter plate...
Also, PE, do you ahve any contact info. for said Autochrome expert??
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Yes, please contact me for name and e-mail.
PE
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I've been making some progress here, so here's a status update. I have dyed starch grains red, green, blue, violet and orange. I have all of these colors should I need them.
I'm currently experimenting with ways to coat these onto the plate. I've come up with a few different ideas, with varying degrees of success:
1.) Mix with adhesive, then coat: This sort of works, but results is a coating that is far from a monolayer; on hold for now.
2.) Sprinkle [great technical term] the starch onto an adhesive: Difficult to prevent tiny grains from clumping, hard to coat an even monolayer.
3.) Brush coating: The plate is coated with an adhesive, and then the starch is lightly brushed on. This works well, though care must be exercised not to put brush marks in the adhesive base. It is definetely doable, especially if pressure is applied to the plate after the coating is done.
4.) Coat plate wiht adhesive, submerge in liquid with suspension of starch: Basically, I mix the starch with water, place the plate in a container and pour the water / starch into it. The plate is then lifted, creating a coating of starch. This works ok, but has the issue of water remaining on the plate and disturbing hte adhesive / speading the starch around. Perhaps it would work with water containing a surfactant or some other liquid (acetone or ethanol, perhaps?)
For adhesive, i've experimented with everything from honey to epoxy. Epoxy seems to work well, though it hardens a little more quickly than I'd like.
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An idea just occured to me. Ever seen those faux stained glass kits where you put the plastic stuff in the wire frame and heated it in the oven? If this kind of stuff could be gotten in the right size granules, mixed, and spread on glass in an even layer perhaps with some vibration to make it settle, then heated to make it bond to the glass. Result would be pretty much what you need wouldn't it?
Another thing may be to mix your starch with a dry powder that will fuse when heated to a temp low enough to not damage the starch. What that powder would be I'm not too sure of. Some kind of high temp wax maybe.
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I like that Idea. The main problem is that when melted, the stuff tends to bleed together, forming gooey gradients in plastic. However, I could simply grind the particles to a small size, and place them ina monolayer, with some moderate heating, or just spread some epoxy over them. That's an EXCELLENT idea.
I'll see if I can find one of those, though not sure where.
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