Perlite is a generic term for naturally occurring siliceous rock. It is a form of natural volcanic glass with 70-76% amorphous silica). It expands 4-20 times its original volume, when rapidly heated to its softening temperature range (above 850^oC), due to the presence of “combined water” (2-6%). Perlite expansion is taking place as the H₂O molecules vaporize and create numerous tiny bubbles, which account for its exceptional physical properties and mainly its’ cellular structure, light weight (30-150 kg/m3) and low thermal conductivity.

AP Expanded Perlite Grades