Patent ID: 7648930

Claim:
A method of making a glass for a fluorescent lamp with a high hydrolytic resistance, said method comprising melting a raw material to form a glass melt, said glass melt having a composition, in percent by weight on the basis of oxide content of: SiO 2 63-75 B 2 O 3 15-18 Al 2 O 3 3.2-4.5 Na 2 O 1-2 K 2 O 2-6 MgO 0-8 CaO 0-10 SrO 0-10 BaO 0-10 ZnO 0-5 ZrO 2 0-3 CeO 2 0-10 Fe 2 O 3 0-1 WO 3 0-3 Bi 2 O 3 0-5 MoO 3 0-3 TiO 2 0-10, at least one refining agent in a sufficient amount for refining the glass melt; and wherein a sum total amount of Na 2 O+K 2 O is 3 to 8% by weight; a sum total amount of MgO+CaO+SrO+BaO+ZnO is 0 to 10% by weight; a sum total amount of Hf+Ta+W+Re+Os+Ir+Pt+La+Pr+Nd+Sm+Eu+Gd+Tb+Dy+Ho+Er+Tm+Yb+Lu in oxidic form is 0 to 5% by weight; and a weight ratio of Na 2 O to K 2 O is 0.2 to 0.5; and containing no lithium except for an amount of said lithium up to 100 ppm due to the presence of impurities; and wherein said glass has a hydrolytic resistance class of 1 or 2.