SILICATE GLASS ALUMINO-ALCALINOTERREOS WITH HIGH THERMAL CAPACITY DESTINED TO BLISTERS OF ILLUMINATI

The invention relates to alumino earth-alkali silicate glasses for molybdenum glass fusions in the form of light bulbs, as the outer shell for lamps, in particular for lamps with regenerative halogen cycles at bulb temperatures of from over 550° C. up to 700° C. Surprisingly and contrary to the current expectation it was found that alumino earth-alkali silicate glasses with a water content of 0.025 to 0.042 wt. % meet the requirements for halogen lamp glass and do not display any disadvantages due to the presence of the above impurity for the halogen cycle process at bulb temperatures of between 550 and 700° C. In glasses with a water content of from 0.025 to 0.042 wt. % the water present does not act as an impurity in the sense that it does not disturb the equilibrium between formation and decomposition of tungsten halides. A blackening of the inner surface of the bulb does not occur, or not a greater degree when compared with bulb glasses with a considerably lower water content.