Good day to all in Orchid land Can any of you rock
hounds, GG's or a more knowledgeable person than myself explain why
an amethyst (at least that's what I thought it was), that has been
coated with heat shield, lots of it, would turn clear for a repair?
I have used heat shield before on amethyst's with out a problem .
Since the color was not real dark to begin with but I thought heat
would make it darker not clear. Is it safe to say that it was never
an amethyst? Thanks in advance for your responses.
Amethyst, when heat treated, first turns clear, and in some cases,
pale green. With further heating, it turns to citrine.
Heat shield is an aid to heat protection, but not fool proof. It
acts as a heat sink, but only if you’ve got enough of it that it
doesn’t dry out, in which case the water content of the stuff is
what’s keeping your stones cool. It’s other function is to
physically block contact with your stone from the direct flame. But
if the compound dries out too much from perhaps prolonged heating,
then while it may prevent direct flame contact, it will still allow
the stone to warm up. It’s more likely to survive without cracking,
since the shielding will help prevent sudden heat shock, but it still
can get plenty hot. And that can easily alter the color.
In general, use heat sheild only as a last resort. It’s such a
thick paste that any heating of the metal under it quickly dries it
enough that it can shrink away from the contact with the hot surface,
at which point it’s cooling effect stops, allowing heat to travel
further into the area contacting the stone. It’s sometimes the only
way to work on a piece without removing a stone, but it can be tricky
stuff. When you use it, the more you use, the safer it will be thin
films don’t do much but protect the surface from direct contact with
the flame. Better, if you can do the work with the stone in this
position, is simply to set a small cup of water on your soldering
station, and immerse the half of the ring(etc) with the stone under
water, leaving the portion to be soldered above water. Because it’s
liquid, any water evaporated by contact with hot metal is instantly
replaced, so the stone is still cooled by the water, never getting
significantly above the boiling point of water, which is still a
safe temp for amethyst. Variations are using a container filled with
sand, which is then saturated with water, or a wad of cotton or
tissue paper soaked with water, wrapped around the area to be
protected. In both cases, the water can still flow back around an
area, even if the sand or tissue isn’t in direct contact.
Hope that helps.