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A slurry composition for a mold and method of use thereof. The slurry composition includes about 45-80% by weight alumina, about 10-30% by weight silicon carbide, and about 10-50% by weight colloidal silica. In one aspect, the alumina component comprises a material selected from the group consistin

A slurry composition for a mold and method of use thereof. The slurry composition includes about 45-80% by weight alumina, about 10-30% by weight silicon carbide, and about 10-50% by weight colloidal silica. In one aspect, the alumina component comprises a material selected from the group consisting of brown fused alumina, white fused alumina, tabular alumina, calcined alumina, and mixtures thereof. In another aspect, the composition includes fumed silica at 2-5% by weight. The composition may also include a setting agent at 0.05-2% by weight.

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What is claimed is: 1. A slurry composition for a mold comprising about 45% to about 80% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to abo

What is claimed is: 1. A slurry composition for a mold comprising about 45% to about 80% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica binder; about 0.01% to about 1% by weight welan gum; and a setting agent. 2. The composition of claim 1, wherein the silicon carbide has an average particle diameter of about 30 micrometers to about 3.5 millimeters. 3. The composition of claim 1, wherein the silicon carbide is present at about 12% to about 25% by weight. 4. The composition of claim 1, wherein the alumina component is present at about 50% to about 65% by weight. 5. The composition of claim 1, wherein the alumina component comprises a material selected from the group consisting of brown fused alumina, white fused alumina, tabular alumina, calcined alumina, and mixtures thereof. 6. The composition of claim 1, further comprising about 2% to about 6% by weight free carbon. 7. The composition of claim 6, wherein the free carbon is present in the form of pitch. 8. The composition of claim 1, further comprising 2% to about 5% by weight fumed silica. 9. The composition of claim 1, wherein the setting agent is present at about 0.05% to about 2% by weight. 10. The composition of claim 9, wherein the setting agent is magnesia. 11. The composition of claim 1, further comprising 0.05% to about 0.5% by weight polypropylene fiber. 12. A casting method, the method comprising: providing a meltable patterned substrate; coating the substrate with a slurry composition; allowing the slurry composition to set and form a mold; and removing the substrate from the mold; wherein the slurry composition comprises about 45% to about 80% by weight alumina; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica; about 0.01% to about 1% by weight welan gum; and a setting agent. 13. The method of claim 12, wherein the substrate is coated with the slurry composition by dipping the substrate into the slurry composition. 14. The method of claim 12, wherein the substrate is coated with the slurry composition by spraying the slurry composition onto the substrate. 15. The method of claim 12, wherein the substrate is coated with the slurry composition by brushing the slurry composition onto the substrate. 16. The method of claim 12, wherein the silicon carbide is present at about 15% to about 25% by weight of the slurry composition. 17. The method of claim 12, wherein the alumina component is present at about 50% to about 65% by weight of the slurry composition. 18. The method of claim 12, wherein the slurry composition further comprises about 2% to about 6% by weight free carbon. 19. The method of claim 12, wherein the slurry composition further comprises fumed silica at about 1% to about 5% by weight of the slurry composition. 20. The method of claim 12, wherein the slurry composition further comprises about 0.05% to about 2% by weight setting agent. 21. The method of claim 12, wherein the slurry composition further comprises 0.05% to about 0.5% by weight polypropylene fiber. 22. The method of claim 12, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition. 23. A casting method, the method comprising: providing a meltable patterned substrate; coating the substrate with a slurry composition; allowing the slurry composition to form a mold; and removing the substrate from the mold; wherein the slurry composition comprises about 45% to about 65% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica; about 0.01% to about 1% by weight welan gum; and a setting agent. 24. A casting method, the method comprising: providing a meltable patterned substrate; coating the substrate with a slurry composition; allowing the slurry composition to form a mold; and removing the substrate from the mold; wherein the slurry composition comprises about 45% to about 65% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica; about 0.01% to about 1% by weight welan gum; and providing a setting agent in the slurry composition, such that a set time can be controlled by varying the amount of setting agent. 25. The method of claim 24, wherein the set time is between 15 minutes and 10 hours. 26. The method of claim 24, wherein the setting agent is magnesia. 27. The method of claim 24, wherein the substrate is coated with no more than three coats of the slurry composition. 28. The method of claim 24, wherein the substrate is coated with no more than two coats of the slurry composition. 29. The method of claim 24, wherein the substrate is coated with a single coat of the slurry composition. 30. A slurry composition for a mold comprising about 45% to about 80% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica binder; about 0.01% to about 1% by weight polysaccharide gum; and a setting agent. 31. The composition of claim 30, wherein the silicon carbide is present at about 12% to about 25% by weight. 32. The composition of claim 30, wherein the alumina component is present at about 50% to about 65% by weight. 33. The composition of claim 30, further comprising 0.05% to about 0.5% by weight polypropylene fiber. 34. A casting method, the method comprising: providing a meltable patterned substrate; coating the substrate with a slurry composition; allowing the slurry composition to form a mold; and removing the substrate from the mold; wherein the slurry composition comprises about 45% to about 65% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica; and about 0.01% to about 1% by weight polysaccharide gum; and a setting agent. 35. A casting method, the method comprising: providing a meltable patterned substrate; coating the substrate with a slurry composition; allowing the slurry composition to form a mold; and removing the substrate from the mold; wherein the slurry composition comprises about 45% to about 65% by weight alumina, wherein the alumina component comprises particles of between about 1.1 to about 3.0 mm in diameter at about 0% to about 10% by weight of the composition, particles of between about 0.2 to about 1.1 mm in diameter at about 40% to about 60% by weight of the composition, and particles of about 0.150 mm in diameter at about 2% to about 10% by weight of the composition; about 10% to about 30% by weight silicon carbide; about 10% to about 50% by weight colloidal silica; about 0.01% to about 1% by weight polysaccharide gum; and a setting agent in the slurry composition, such that a set time can be controlled by varying the amount of setting agent. 36. The method of claim 35, wherein the substrate is coated with a single coat of the slurry composition. 37. The method of claim 35, wherein the slurry composition further comprises 0.05% to about 0.5% by weight polypropylene fiber.