Patent ID: 7037868

Claim:
A method of forming a protective glaze surface on an architectural tile comprising: providing a ceramic body; applying a glaze composition to the ceramic body, the glaze composition comprising a zinc-free glass frit consisting essentially of, by weight, from about 50% to about 70% SiO 2 , from about 5% to about 20% CaO, from about 3% to about 15% Al 2 O 3 , BaO, provided that the content of BaO does not exceed about 20%, up to about 15% B 2 O 3 , up to about 10% K 2 O, up to about 6% Na 2 O, up to about 10% ZrO 2 , up to about 5% MgO and up to about 5% PbO; and firing the ceramic body to fuse the glaze composition to a surface thereof.