I have a great casting company for you to look at gsjewelrymfg.com,
they use modern casting machines with oxygen free casting
environment, theycast all types of golds, bronze and de-ox. silver.
they use vacuum investment mixers with de-ionized water, they can
make molds as needed, they have been around for over thirty years.
I have been using them for over ten years, very nice people, ask for
Tom the owner.