The present study focused on the effects of argon pressure, mold venting, and investment permeability on the mold filling of titanium and the soundness of titanium castings. Casting soundness was determined by density measurement and x-ray radiography. To achieve complete filling of molds made from a relatively impermeable investment, the molds were vented. Regardless of the presence or absence of vents, all of the molds made from a highly permeable refractory material filled completely. The soundness of castings made under an argon pressure of 50 torr was significantly greater than that of castings made under a pressure of 400 torr. The non-vented molds of the highly permeable refractory material yielded the soundest castings (mean density = 4.45 g/cm3).

Mold filling and porosity in castings of Ti.
Herø H, Syverud M, Waarli M
Dental Materials 1993 Jan ; 9(1): 15-18