How hot does glass have to melt into a liquid?

Question

our 100 year old barn just burned to the ground and i found a glass icicle hanging from a tractor headlight and we wanted to know how hot the fire was. thanks

Answer 1

Glass will fuse flat at about 1550F and flow around objects at up to 100F below that.  If the bulb had an icicle, it was exposed to temps in that area at least for a while.   It can sag and droop in the 1250-1300F range.   Since it was a tractor, perhaps there was extra local heating from the fuel in the tractor.

  Glass is an amorphous solid, meaning it is not crystalline, but is hard as rock.  Liquids are amorphous but that does not mean amorphous solids are liquid - just a bit like one.

A supercooled liquid is a liquid - like water cooled to 30F that instantly forms ice when a crystal is added.

Answer 2

If the "icicle" was glass, the fire reached approximately 2000 degrees F. That sounds kind of high for a barn fire - it might have been a plexiglass or similar material.

FYI: Glass is  an amorphous solid - kind of like a material between a solid and a liquid.

Answer 3

Depending on it's composition, glass has a melting point of 1400-1600 °C.

http://hypertextbook.com/facts/2002/SaiL...

Pure silica (SiO2) has a "glass melting point"— at a viscosity of 10 Pa·s (100 P)— of over 2300 °C (4200 °F).

http://en.wikipedia.org/wiki/Glass

Answer 4

glass is already a liquid or more pacifically a "supercooled liquid"