Glass mold material for precision glass molding

A method for forming molding tools for molding glass optical elements therewith, the glass optical elements having molding temperatures in the range of from about 400° C. to about 825° C., the method comprising the steps of:

• (a) forming a working mold preform from an yttria aluminosilicate glass having a viscosity of less than about 102 poise at a temperature of less than about 1200° C.;
• and
• (b) molding a working mold tool from the working mold preform, the working mold tool including a molded optical element forming surface, the working mold tool having a viscosity of at least about 1015 poise at a molding temperature of the glass optical elements to be molded therewith.

A method for forming molding tools for molding glass optical elements therewith, the glass optical elements having molding temperatures in the range of from about 400° C. to about 825° C., the method comprising the steps of:

• (a) forming a working mold preform from a rare earth aluminosilicate glass having a viscosity of less than about 102 poise at a temperature of less than about 1200° C. and having a Tg that is at least about 50° C. greater than the molding temperature of the glass optical elements, the rare earth aluminosilicate glass having a coefficient of thermal expansion in the range of from about 25×10−7/° C. to about 70×10−7/° C.;
• and
• (b) molding a working mold tool from the working mold preform, the working mold tool including a molded optical element forming surface, the working mold tool having a viscosity of at least about 1015 poise at a molding temperature of the glass optical elements to be molded therewith.