Composite glass articles spontaneous opal glass and enamel of Li. sub.2 -O- B.sub.2 -O.sub.3 -TiO.sub.2 -ZrO.sub.2 -PbO-SiO.sub.2

摘要

This invention relates to the production of a composite article consisting of an opal glass body exhibiting a dense, milky-white appearance coated with an adherent enamel demonstrating high gloss and exceptional chemical durability. More specifically, the opal glasses of the present invention have compositions within the Na.sub.2 O-Al.sub.2 O. sub.3 -SiO.sub.2 -F system and demonstrate a softening point in excess of 760° C., a strain point in excess of 490° C., and a coefficient of thermal expansion (0°-300° C.) of about 66- 75 × 10.sup.. sup.-7 /° C. The enamels of the instant invention have flux compositions within the Li.sub.2 O-B.sub.2 O.sub.3 - TiO.sub.2 -ZrO.sub.2 -PbO-SiO.sub.2 system, will fire to a high gloss in less than about 10 minutes at temperatures below about 720° C., will exhibit coefficients of thermal expansion (25°-300° C.) about 3-10 points lower than the opal glass substrate, will demonstrate lead release after chemical attack of less than about 2 &mgr;g/cm.sup.2, and will manifest excellent resistance to dishwasher detergents.