The raw material for perlite production is volcanic silicate rock that cooled down rapidly in sea water after the eruption of underwater volcanos. The Greek island of Milos and Hungary have the most important reserves of perlite in Europe.
The material is crushed, sifted to a defined particle size and heated to approximately 1,000 °C. At this temperature, the water trapped in the perlite vaporises, expanding the molten glass to 20 times its original size. This expansion produces a light-weight neutral material with closed nuclear pores, open peripheral pores and very good water holding capacity.