Heat Treated (Caramelized) Fiberglass Cloth is a kind of cloth, specially heat-treated to suitable for a specific application.

The normal fiberglass cloth is put into a high temperature stove to burn off the sizing and other organic elements within the cloth. After the treatment, the cloth color becomes brown.

The most important feature is Smoke free.  
 
Application: 
There is No difference from normal fiberglass fabrics, but especially for the applications where smoke is not allowed.