Yes, that is the question--but let's look a bit further. Glue on the
back of a faceted stone is another issue, it eliminates internal
reflection, it lets the light out, it's a no-no!
But a bezel is fit to hold a cab in horizontal position and formed
over to hold it down. If a "glue" is added it's real purpose is to
ensure total contact of the bottom of the cab with the back of the
mounting, no rocking, wiggling or rattling. Our colleagues in the
world of gunsmithing have a perfect word for this--BEDDING. In their
work it is usually epoxy used to BED a metal part against properly
fit wood, with the epoxy adhering only to the wood.
So let's introduce the concept of BEDDING to bezel setting, as
"these gorgeous stones are elastomer bedded in their hand crafted
Argentium sterling bezels".