Glass
From Roofing, Solar Power, and Spray Foam Insulation Wiki
Glass
A hard, brittle substance, usually transparent, made by fusing silicates under high temperatures with soda, lime, etc.
See also: Glass Felt, Glass Mat, Chopped Glass and Emulsion (CG&E), Glass Eyes Or Glass Windows, Glass Fiber Felt , Glass Fiber Mat, Bent Glass, Flat Glass, Float Glass, Fully Tempered Glass