Patent ID: 8911824

Claim:
A method of sealing an inner surface of a refractory crucible with a ceramic, comprising the steps of: (a) heating a refractory crucible to a temperature between about 100° C. and about 150° C., said crucible having an inner surface defining a material-containing cavity and an outer surface; (b) applying a wetting agent to said inner surface of said crucible; (c) applying a ceramic slip having a viscosity of about 100 to 3,500 centipoise along the surface of said crucible, said ceramic slip comprised of water, a wetting agent/dispersant and about 20% to 80% by weight of ceramic powder, at least 90% of said ceramic powder having a particle size of less than 1 micron said ceramic slip is applied to the inner surface of said crucible by filling said crucible with said ceramic slip; (d) applying a vacuum to said crucible to draw said ceramic slip into the inner surface of said crucible; (e) removing excess slip from the inner surface of said crucible; (f) heating said crucible to remove moisture therefrom; and (g) firing the crucible at a temperature between 1,300° C. and about 1,700° C. for about 2 to about 6 hours.