Abstract: The present invention relates to a process for the production of a glass from silica as a raw material by a vacuum melting method, in which a high quality glass is produced efficiently by compounding a silica powder containing an excess amount of the accelerator for phase conversion and silica powders containing substantially no such accelerator or by introducing silica powders in a solution containing an accelerator for phase conversion, adding an acid or basic component to the mixture to adjust the pH thereof, stirring the mixture for mixing, and subjecting the mixture to dehydration and drying to obtain silica powders containing the accelerator for phase conversion in proper quantities, filling the resultant silica powders in a vessel and heating the powder to form a sintered molded body having cristobalite phase having a self-supporting property and also having a proper matrix strength and a high porosity, and then heating the sintered body under vacuum.

Abstract: A process for production of a glass by a vacuum melting method using silica as raw materials comprising heating silica powders in the presence of an accelerator for phase conversion to convert them into a sintered body having cristobalite phase; molding or repowdering the sintered body; containing or filling the resulted sintered body in a container having a desired shape; and then heating and melting it in vacuo for glass formation, or accumulating a plurality of the sintered bodies into a desired shape; and then heating and melting it for glass formation, whereby a high-quality glass ingot having a desired shape or a larger glass ingot can be readily obtained without reduction in productivity.

Abstract: The present invention relates to a process for production of a glass by the vacuum melting method using silica as raw material and comprises uniformly preheating a silica powder containing an accelerator for phase conversion to about 800.degree. C.; filling the preheated silica powder in a container while substantially maintaining the temperature; further heating the silica powder to convert it into a sintered body having a cristobalite phase; and then heating and melting the sintered body in vacuum for glass formation, whereby not only are improvments in raw material efficiency and productivity by shortening of the heating time achieved, but also the formation of cracks on the surface of the resulted sintered body which has been one of the important reasons for resulting in products of sub-standard can be substantially completely avoided.