Patent ID: 7128129

Claim:
A mold-forming composition for use in producing an investment casting shell, the mold-forming composition comprising: a colloidal silica providing 20.3% to 37.5% of the mold-forming composition's weight; a zircon flour providing 15.2% to 35.6% of the mold-forming composition's weight, wherein most of the zircon flour has a zircon particle size of 200 mesh to 350 mesh; a fused silica providing 12.9% to 21.3% of the mold-forming composition's weight, wherein most of the fused silica has a silica particle size of 90 mesh to 150 mesh; an alumina providing 6.4% to 27.8% of the mold-forming composition's weight, wherein most of the alumina has an alumina particle size of 50 mesh to 325 mesh; and a thickness-promoting material providing 0.7% to 2% of the mold-forming composition's weight, wherein the following is true: a) the fused silica plus the alumina combined provide 21.2% to 40.7% of the mold-forming composition's weight, b) the fused silica plus the zircon flour combined provide 28.1% to 56.8% of the mold-forming composition's weight, and c) the zircon flour plus the alumina combined provide 35.6% to 47.2% of the mold-forming composition's weight.