Casting diamonds in place

Hi all, I am looking to cast one of my bracelets in glass, and since
my bracelet has a series of flush mount set black diamonds, i figure
the only way to set these in glass would be to use cast in place
diamonds. I remember once though that when you cast diamonds in place
you have to add a certain amount of acid to the investment, by weight
to prevent the investment from eating the diamonds during the
burnout. what i don’t remember is, what kind of acid to use, and how
much of it to use. the process of casting glass is similar enough to
casting metal that i feel fairly confident that the process should
work the same, so whatever anyone knows about casting diamonds in
place in metal should be useful to me for this glass project.

thank you all for any answers you can give me


As I recall it was boric acid, which maybe would also accelerate the
investment hardening. Consider the “Extreme” investments made for
white gold. Kerr has one as do others. I would love to see a picture
of your final result posted. What a look!!! Diamonds in glass.

Daniel Ballard


Start with this article:

I think it will answer all/most of your questions. It’s a
well-written and researched article on stone-in-place casting.

The other consideration (and I’ve had less trouble with black
diamonds than white in this area) is that the stone not get “frosted”
or burned. That means modifying burnout a bit and being careful with
casting temperatures.

Hope this helps!

Karen Goeller
No Limitations Designs
Hand-made, one-of-a-kind jewelry

You might find that the diamonds will burn out during the
casting/annealing process. The time frame is just so much longer than
for investment casting metals, yes the initial burnout is about the
same length of time, but the casting (when the glass will flow) is at
a much higher temp than for metal casting (most glass will flow at
between 1200’F [real slow flow rate] to 2200’F [glass blowing temp])
and then you have to anneal the piece this can take a few hours to
days depending on cross section and mold thickness.

Good luck.
Cheers, Thomas.
Janstrom Designs.

PS. We also do glass art; cast, fused and slumped. But no flame work!