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Opal Sealant


#1

The problem with the stone I got is that it isn’t polished or shiny
like the ‘broken glass’ sheen that was mentioned as a possibility.
It’s more like a satin finish, and mostly flat but very slightly
uneven. It does have nice color while dry, but it really sparkles
when it’s wet, which is why I was thinking some kind of clear coating
would do the same. If it helps to ID it any further, it’s from
Australia and I think it’s some kind of leftovers from cutting black
opals (which is why the layer is thin?).

    the spray on acrylic plastic coatings, such as Krylon.  It's
colorless, pretty durable, and has a high enough refractive index
to look reasonably bright for a coating. 

That sounds pretty good. Is that something one can buy at the
average hardware store?

–Marcy


#2
It's more like a satin finish, and mostly flat but very slightly
uneven. It does have nice color while dry, but it really sparkles
when it's wet

Marcy, this sounds like an opal “rub.” These are opals the
Queensland cutters reject for one reason or another after grinding
and sanding on them. Some are obviously “sand-shot,” others have bad
shape or the color may have opaque areas, etc. Rather than lose
everything, they sell them at low prices to others willing to gamble
they can turn them into decent stones. Some are real challenges but
I’ve managed to cut some very valuable opals from “rubs.”

It sounds as if yours can probably be polished by normal means if
you can find someone to do the work. If you can’t I’d recommend
mixing a small amount of Epoxy 330 or the slow-drying (overnight -
not 5-minute) hardware store equivalent. Just make sure it dries
crystal-clear. Mix a small amount per the instructions then heat it
gently under a light bulb briefly to let the bubbles rise to the
surface and, hopefully, pop. This also makes it more liquid. Lay
the stone on a piece of aluminum foil and gently paint the epoxy on
with a small artist’s brush, taking pains to avoid drips. Plan on
disposing of the brush unless you want to clean it in acetone. When
you’re done heat the stone again for a minute or so under the light
to eliminate bubbles. Sometimes you can brush them to the edge. Let
the stone dry overnight.

It’ll probably be stuck to the foil after drying - try to avoid
drips. If they happen you can peel the foil off and gently remove
unwanted epoxy with an X-acto knife or scalpel. This should give you
a “polish” that’s permanent, durable and that looks almost natural.

Rick Martin
MARTIN DESIGNS