Fiberglass fabric Used as welding blanket and insulation lining to protect sensitive machineries, HT800 is effective! Fiberglass fabric Glass Fiber Fabric light and heat treated satin weave pattern results in thicker, heavier and stronger Fabric far more resistance to heat impact from welding sparks. We have our fiberglass cloth pass through a oven with high temperature in order to burn off the sizing and other organic elements in the cloth.After this heat treatment,fiberglass cloth will change to brown color and it will be smoke-free during the application.