There is a gray chemical painted on the back of glass gems,
crystals, etc., etc. What is this chemical and where can I purchase
it.
To create the sparkle, the back of the gem is /silvered. /The process
is the same as that used for making a mirror out of a sheet of glass.
Years ago a very thin film of pure silver was applied via a chemical
process, but now days a thin coat of aluminium is usually used.
Since the film is very thin and delicate, it needs protecting; and
that is done by a coat of paint - usually grey. Its not the grey
chemical that you see that causes the sparkle, its the thin metal
film that’s underneath the grey.
Its possible to silver the back of a gem yourself, but its not
particularly easy. I suspect that a coat of /proper /silver paint
would work reasonable well, though not quite as good as real
silvering.