Abstract A system of thermally opalizable glass compositions, suitable for use in making opal glass containers and low-expansion, heatresistant ovenware consisting essentially of SiO2, Al2O3, B2O3, CaO, MgO and Na2O in specified critical amounts. The thermally opalizable glass compositions that can be used to form glass containers at low cost by conventional high-speed glass-forming techniques have the following ingredients in approximate percentages by weight: Ingredients Percent Si02 66-69A12O3 6 B2O3 4-8 CaO+MgO 1318Na2O 5 in which the weight percent ratio of CaO:MgO is about 1.4. Preferably, an article is formed of the above glass composition, and heat-treated to provide an in situ glass-in-glass phase separation by maintaining the article at a temperature in the neighborhood of 1,050* to 1,500* F. for about 1/4 to 8 hours.
A thermally opalizable alkaline earth aluminosilicate glass composition of claim 1 having the composition: SiO2 67-69% Al2O3 6 B2O3 4 CaO+MgO 16-18 Na2O 5
Claim 2
Dependent Claim
21 words
A thermally opalizable glass composition of claim 1 having the composition: SiO2 66.5-68.5% Al2O3 6 B2O3 6 CaO+MgO 14.5-16.5 Na2O 5
Claim 3
Dependent Claim
21 words
A thermally opalizable glass composition of claim 2 having the composition: SiO2 66-68% Al2O3 6 B2O3 8 CaO+MgO 13-15 Na2O 5
Claim 4
Dependent Claim
77 words
A thermally opalizable alkaline earth aluminosilicate glass composition consisting essentially of silica, alumina, B2O3, CaO, MgO and Na2O in which the weight percent of CaO:MgO is about 1.4, the amount of Al2O3 being 6 percent by weight, the amount of Na2O being 5 percent by weight, and the relative proportions by weight of SiO2, B2O3 and CaO+MgO being defined by the area bounded within the heavy lines of the ternary diagram of FIG. 1 of the drawings.