From memory (of a happy couple of hours spent with a glass blower on the Isle of Wight) the temperature in his furnace was about 2000degrees C. Also visited the glass works at Nazeing (
http://www.nazeing-glass.com/) on a number of occasions and they also spoke of temperatures in excess of 2000 degs C
As I understand it glass doesn't so much melt as soften because it is not really a "solid" but what is known as an amorphous solid. This means it doesn't crystallise in the "hardening " process. Obviously there will come a temperature at which it will soften to a point where it will become liquid (melt) but I cannot imagine that any domestic application could achieve that temperature. My late FiL was the expert but unfortunately is no longer able to help. He did have a hand in developing the "tiles" that shield the shuttle as well as the insulation materials used in Nuclear and conventional power stations. He spent years studying the properties and "meltability" of glass and glass fibre. His estate still enjoys a small income from his patents on cavity wall insulation materials and the Shuttle insulation.
