My best advice is have it done for you! Platina Casting Services
(1-800-401-7257) is my favorite, but many dental laboratories
cast platinum and they are local to you.
Do you have a machine designed for casting platinum? I know of
at least one craftsman that casts platinum on his standard
casting machine. He put a super heavy spring in it to give the
necessary acceleration.
You need to get the platinum HOT!!! I mean VERY HOT! You can’t
oxidize platinum, so try using a oxidizing flame, about 5 lbs of
hydrogen and 40 lbs of oxygen, that will give you the heat
necessary. Other casters tell me they use 60 lbs each of O2 and
H2, now that’s a big flame. My favorite is induction, just wish I
had my own!
You didn’t say what kind of shapes you’re casting, so I’ll give
some general advice. Use multiple sprues. Platinum solidifies
very quickly and you need to get a complete fill while the
platinum is fully fluid.You can get a great looking casting that
breaks into pieces with one hit from a hammer. A good casting
will have a shiny, albeit rough texture, the same sort of look
you get from a freshly melted piece, I guess the word is FUSED.
Platinum is funny stuff, you can get a perfect casting that is
NOT fused. An unfused casting is like compacted sand. It polishes
to a high finish, and sometimes can be worn for years, then fall
into pieces while being sized.
It’s been a number of years since I did my own plat casting, so
I don’t know what investments are recommended now.
Good luck, and wear dark glasses! 
Jeffrey Everett
Hiya,
I have recently been asked to do some platinum casting for a
friend of mine. This will be a first for me, so I was looking
for a few pointers. Best to learn from the experiance of
others!
I would like to know if anyone can tell me of any major
diffrences between casting gold alloys versus platinum. ( appart
from temp of course ). Also I need to know of a good source for
platinum casting grain, findings and wire if possible. I am
already set up for oxy/hydrogen. I would be gratefull for any
advice on this matter.
Jeffrey Everett, jewelry craftsman
Handmade 18K, 22K, and platinum gemstone jewelry.
Diamond setting, rubber/metal molds, casting, lapidary
Die and mold engraving, plastic patterns for casting.
Cad jewelry design, cad/cam milling scroll filigree…
P O Box 2057 Fairfield IA 52556 515-469-6250