We are very pleased with our new closed-system, oxygen-free casting machine! When we cast, there is no oxygen anywhere in the system, and that's important - our gold is oxygen free. (Casters who don't use a system similar to ours often have "cheesy gold", that is, they produce gold that is internally pitted with tiny bubbles originating from oxygen present during the cast. Cheesy gold is often the cause of broken prongs and broken or cracked ring shanks.)
When we cast, we flood the melting chamber with nitrogen, forcing out all oxygen. The melting crucible, where the gold is actually melted, is made of graphite, which also removes any trace amounts of oxygen that might be present.
Before we squeeze the lever that drops the molten gold, we pull a strong vacuum in the flask that ensures that the molten gold is pulled into every tiny nook and cranny — all of the filigree, all of the prongs, everything has molten gold pulled into it before it hardens.
