Best rubber mold for casting white metal

I’ve taken on a job to reproduce a lost costume jewelry earring from
the remaining earring. I took it on as a challenge and a learning
experience rather than as a money-maker.

The earring I need to copy is sort of a Southwest style made of
white metal with a plastic “turquoise” cab (no veining). I can
duplicate the cabochon with polymer clay and glaze, no problem.

I’m going to make a new pair of earrings so the weights match, and
turn the original remaining earring into a pendant. I bought some
lead-free white metal and a melting ladle. But I can’t seem to find
out exactly which mold rubbers can handle having approx. 600F molten
white metal poured into them. I found lots of references online where
people were “going to try” casting white metal in one kind of rubber
or another, but nobody has ever gone back and posted results
anywhere!

I have here:

Castaldo gold vulcanizing rubber (I’d prefer not to use this one due
to the larger shrinkage factor)

Castaldo Gelato silicone vulcanizing rubber

Dow Silastic E liquid RTV silicone rubber

A sample size of Castaldo Liquicast RTV

Which, if any of these materials would be able to handle two pours
of molten white metal directly into the mold?

I don’t have spin casting capability and I don’t want to acquire it
just for two earrings. [smile]

Kathy Johnson
Feathered Gems Jewelry
http://www.featheredgems.com
http://www.fgemz.com