Patent ID: 8115044

Claim:
A silicate-based glass comprising: rock-forming components selected from the group consisting of SiO 2 , Al 2 O 3 , ZrO 2 , alkaline earth oxides, alkaline oxides and mixtures thereof; and glass-forming components selected from the group consisting of SiO 2 , Al 2 O 3 , ZrO 2 , B 2 O 3 , P 2 O 5 , TiO 2 , Li 2 O, F, alkaline earth oxides, alkaline oxides and mixtures thereof; said silicate-based glass consisting essentially of: about 1.6 to about 2.2 parts in weight percent of a combination of monovalent cation oxides (R 2 O) and divalent cation oxides (RO); about 1 part in weight percent of trivalent cation oxides (R 2 O 3 ); about 1 to about 3 parts in weight percent of a combination of tetravalent cation oxides (RO 2 ) and pentavalent cation oxides (R 2 O 5 ); and wherein Na 2 O is present in an amount greater than 23 weight percent, Al 2 O 3 is present in an amount greater than about 13 weight percent and less than about 20 weight percent, SiO 2 is present in an amount greater than about 30 weight percent and less than about 48 weight percent, and B 2 O 3 and other flux components are present in a total amount greater than about 9 weight percent and less than about 15 weight percent.