OPTIMUM COMPOSITION OF CERAMIC MASS WITH FUSED CORUNDUM.

A Box-Wilson procedure was adopted to determine the optimum composition of the ceramic mass made from fused corundum, for the facing layer in two-layer investment molds. The solids should consist of 66 parts by weight quartz fines and 34 parts fused corundum, or 3 parts to 1 by volume. The solids contents of the suspension should be 3. 4 kg per litre of hydrolysate, or 54 parts to 46 by volume. The catalyst should be a 32 percent aqueous triethanolamine solution, in the proportion of 1 litre to 18. 5 litre of hydrolysate. The resulting specimens gave a shrinkage of 1 percent and a bending strength of 8 kgf/cm**2. Fine hairline cracks developed on their surfaces after firing. The gelling period was 4 min. The ceramic mass had good flowability and good filling capacity in pockets between a pattern and a false mold.