Aplite is added to container glass and insulation fiber glass batches for alumina.  Alumina (Al2O3) is a minor but important oxide ingredient in glass compositions. Alumina inhibits devitrification and affects the viscosity during glass forming and improves the chemical durability and thermal shock resistance of the finished glass.

Aplite's lower melting point enables the material to disperse easier at the furnace temperatures used in glass making.  In addition, aplite has less tendency to form defects in the glass.

Source:  Montpelier, VA