Cooking utensil with non-stick cooking surface

Claim 1

A cooking utensil having a non-stick coating on at least the food-contacting surfaces thereof, said cooking utensil comprising; a body sheet formed of a material selected from the group consisting of cold rolled steel and enameling iron, said body sheet having a non-stick coating tenaciously secured to the surfaces thereof that are presented toward foods to be cooked, said non-stick coating being of composite construction including an inner layer intimately bonded to the adjacent surface of said body sheet, an intermediate layer intimately bonded to said inner layer and an outer layer intimately bonded to said intermediate layer, said inner layer consisting essentially of porcelain enamel formed of a ground coat frit fired on the adjacent surface of said body sheet, said outer layer consisting essentially of a non-stick plastic material, said ground coat frit consisting essentially of about 82% by weight of a mixture of feldspar and borax and quartz and of about 16% by weight of a mixture of soda ash and sodium nitrate and fluorspar and of about 2% by weight of a mixture of cobalt oxide and manganese oxide and nickel oxide, said intermediate layer consisting essentially of from about 31% by weight to about 60% by weight of said ground coat frit and from about 21% by weight to about 50% by weight of titanium white cover coat frit and from about 3% up to 7% by weight of clay and from about 0.13% by weight to about 0.19% by weight of bentonite and from about 0.21% by weight to about 0.27% by weight of magnesium carbonate and from about 0.13% by weight to about 0.19% by weight of sodium nitrite and from about 11% by weight to about 13% by weight of matting glaze, the sum of the percent by weight of said ground coat frit and said titanium white cover coat frit being in the range from about 79% by weight to about 83% by weight.