Dear ReaDwoW, Your question about “foiling” gems is answered
entertainingly by that great renaissance self-promoter, Benvenuto
Cellini.
Dover Publications regularly reprint his famous Treatises in the
original form of the 1888 translation by C.R. Ashbee. The reprint I
have in front of me is 1967, but I’ve seen it fairly regularly in book
shops since. If you can get a copy, you’ll find all you need to know -
and more - in his Chapter 7, “How to Make Foils for All Sorts of
Transparent Jewels” on page 28, and again in Chapter 10, “How to Give
a Diamond its Reflector”, page 40.
Kind regards,
Rex from Oz.