Strength properties of some gypsum-bonded casting investments.

The present investigations show that there is no correlation between on the one hand the wet and the dry compressive strength of the three gypsum-bonded investments studied and on the other the compressive strength of the investments at burn-out temperature. The study also demonstrated that there is no correlation between the compressive strength and the fracture resistance of sharp edges of the investment mold when exposed to the impact of the casting alloy entering the mold. The inconveniences caused by the fracture of such edges are prevented by a moderate rounding of the corresponding parts in the preparation.