Patent ID: 8636946

Claim:
A bell annealing furnace, comprising: an outer furnace cover encompassing at least one inner cover, each inner cover having inner and outer surfaces forming a space within the inner cover; a heating means disposed within the outer furnace cover to heat the outer surface of the inner cover; at least one high emissivity thermal protective layer at least partially disposed on a substrate surface comprising the inner surface of the inner cover; and means for sealing the inner cover and the outer furnace cover; wherein each substrate surface is metallic, ceramic, or combinations thereof; wherein the high emissivity thermal protective layer comprises, a. from about 5% to about 30% of an inorganic adhesive, from about 45% to about 92% of a filler, and from about 1% to about 20% of one or more emissivity agents; or b. from about 5% to about 35% of colloidal silica, colloidal alumina, or combinations thereof, from about 23% to about 79% of a filler, and from about 1% to about 20% of one or more emissivity agents.