The MEMCO CASTING Advantage
MEMCO casting systems offer several types of noncontaminating, long life ceramic crucibles. On average they last 5 times as long as common graphite crucibles. Graphite crucibles are noted for hardening several metals such as iron, nickel and palladium. As graphite deteriorates, it flakes off and falls into the melt causing inclusions in the cast pieces. Gold has a unique ability to carry carbon into the flask where it reacts with the investment causing microporosity in the casting.
All MEMCO casting systems use hydrogen cover gas to completely eliminate oxygen. Gases such as nitrogen or argon replace some of the air in the crucible but do nothing to remove oxides already present in the metal. Since hydrogen gas is far more reactive than carbon for oxygen removal, it is used by all refiners and knowledgeable casters. Hydrogen cannot be used in closed system casting machines for safety reasons.
The pressure over vacuum concept is not new, in fact, Inresa used this over 30 years ago. Several manufacturers make pressure over vacuum machines and they claim that there is less porosity in the casting. The microporosity caused by the graphite crucible or other sources of carbon supposedly is reduced by the over pressure. An easier way to do the same thing is follow proper burnout procedures and cast with a ceramic crucible!
When you buy MEMCO you get years ahead design with a solid reputation for excellent engineering.