Will glass in a near vacuum melt at a lower temperature? or Does air pressure affect meling point of glass?

Answer 1

I work with furnace glass for glass blowing and I seriously doubt that it would while also being very hard to test. Obviously the glass would have to be heated from an electrical source which would have to be inside the vacuum chamber since heating the chamber and its fittings doesn't bode well at glass melting temps. Glass does not conduct electricity when cold so there would have to be heating coils with a ceramic surface. Glass softens and melts over a range of temperatures so the test would have to based on reaching a specific viscosity. Glass contains a lot of chemicals as oxides and carbonates and one problem is that heat makes these breakdown further and form small bubbles in the glass. A vacuum would aggravate this effect. I have never heard of air pressure significantly affecting melting point (unlike boiling point, where it affects the vapor pressure a lot). Solids do form differently under high pressure, but this is in the thousands of pounds range, not the 15 psi difference of a vacuum.