re: #457 ThomasLite

Ouch. Out of curiosity though, why is that routine? just to lower the melting point? (can’t imagine that’s going to make much of a difference with most metals and it’d seem easier to just fill the chamber with something inert if oxidation is the issue)

Since brass and most precious metal alloys contain copper, we try to get rid of all the air to avoid oxides and o2 absorption. Sometimes with fire or carbon crucibles, sometimes by vacuum, sometimes via displacement of air with argon or nitrogen. When we made purple gold we emptied the chamber 5 times and refilled with expensive argon. Then turned on the heat.

Oh and pressure changes boil temp, but not melt. :-)