These things are making a little comeback. Traditionally they're made by carving porcelain, but I know of at least one company doing something either photomechanically or electromechanically to produce (the molds for) them.

Anyway, to make a long story boring, I was wondering what photomechanical means - such as an etchant - might exist to provide a deep enough relief to produce large format photolithophanes. I'm not thinking so much about etching metal plates as something softer like a plastic or rubber that can be used as a mold.

This seems really far out there to me.

Theres something called a di-litho plate that is used for the older letterpress systems . Its a plastic letterpress plate that is made by photoetching. I've seen and used them but don't know the exact process. The material was maybe 3/16 inch to 1/4 inch thick.

Like the current day photopolymer used for printing? How deeply etched was the relief? Do you recall?

I'd guess about 1/8 inch. It's been a couple of decades since I last laid eyes on the stuff so I can't be exact. Then theres multilevel embossing dies that are done with resists. I know of them but have seen very few of them. They come with a counter die made from plastic that usually is cast from the metal die. At least with this info you might could track down somebody who makes the stuff and find out what it can do.

Cool. 1/8" is probably very close to the deepest lithophanes I've actually held in my hand. There's little chance they were actually hand-carved porcelain; I believe they were machine made. I was inspired when I thought about the possibilities for 11x14 window hangings, 8x10 lampshades or even medium format nightlights. They're cool, but I've yet to see anything written about producing them photographically. Thanks for the lead.

In Alternative Photographic Processes ISBN 1-883403-70-7, Webb and Reed on page 114 mention it may be possible to etch lino with oven cleaner foam, or some other solvent. The resist would be dichromated gum or a carbon print.