One of the major reasons for shell cracking in the investment casting process is the thermal expansion of pattern wax during autoclaving. Parameters of the wax pattern-making process were considered including: injection flow orientation, reclamation procedure, and injection pressure. The effect of glassy and crystalline components of wax structure was examined. Thermal expansion was measured by a non-contact method to ensure true free expansion measurements. Filled and unfilled waxes from production foundries were measured. To provide basis of comparison, two vendor-recommended waxes were studied as well as the Cerita 29-51 wax that has been extensively studied by other investigators (Sabau, 2000).