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[How2Make] foil-backed gems

Speaking of foils, Does anyone know the process to make the foils
used in antiquity for backing gems?

Dear Peter and Stephanie, just for fun, take a trip back in time
and read the charming and entertaining translation of “The
Treatises of Benvenuto Cellini on Goldsmithing and Sculpture” by
C.R. Ashbee. Ashbee, C.R. (trans.) published by Dover (1967)
ISBN 0-486-21568-7, or L of C, 66-13829

Benvenuto’s description on page 28, “Chapter VII. How To Make
Foils For All Sorts of Transparent Jewels” (which is far too long
to copy here - don’t worry, I think it’s over 50 years ago!) is
quite delightful for its mixture of practicality and vainglory.
It might even be useful!

Enjoy, learn and chuckle:) Rex from Oz.

Gadzooks! Petrus and Stephania, …it requires all a man’s
energies to make foils, so I thought I, Benvenuto, would give a
few facts about it for the benefit of anyone anxious to learn.
The first foil is called the common foil, it is of a yellow
colour and is used for many jewels and transparent stones. But
first a word as to the weight of a carat, which is a weight of
four grains.

The foils may be stated in weights thus:

Common (Yellow) Foil.      Blue Foil.
9 carats of fine gold           16 carats of fine copper
18  "      "  silver                    4    "      "  gold
72  "      "  copper                 2    "      "  silver

Red Foil.                                Green Foil.
20 carats of fine gold         10 carats, fine copper
16   "       "  silver                   6    "       silver
18   "       "  copper                2     "       gold

I, Benvenuto, explain in splendid detail how to work these
metals in Signor Ashbee’s passingly good translation of my
Treatises, already referred to by that eccentric dabbler who
carries himself about as Rex from Oz.

Hello All: It is interesting to note that before the art of
diamond cutting got very good. Cutters sometimes would foil back
diamonds. So if you come across an old old item with foil backed
stones, don’t always assume them to be fake. The counter person
brought back a ring about 5 months ago with lots of unevenly
faceted near colorless stones and said that the customer just
inherited this and wanted it cleaned. I tested the stones and
they were diamond with some of the original foil still intact. I
explained to the customer what she had and we left the ring just
as it was.

Michael Mathews Victoria,Texas USA