The problem: Air and gas bubbles can become entrapped in waxes during the injection process. These bubbles can break during the vacuum portions of the investing cycle. If this happens, investment will fill the cavity and result in a hole in the casting. The source: There appears to be at least two sources of entrapped bubbles. The first source is air that is mechanically entrapped during the melting process. The second source is from volatile material in the wax itself. Even a trace of such material could be a problem. The solution: If you have a problem the simplest solution is to vacuum de-gas your wax. This can be done either as a separate operation or in the wax pot.

Author: Dave Schneller