Perlite Ore Sand — Frequently Asked Questions

Because expansion multiplies volume by seven to twenty times, so freighting expanded perlite is largely freighting air. The economics strongly favour shipping the dense ore and expanding it close to the point of use, which is why perlite is traded internationally as ore sand and expanded regionally.

It contains two to five percent chemically bound water. Heated rapidly to between 850 and 1,100 degrees Celsius, the volcanic glass softens at the same moment that water vaporises, and the trapped steam blows the softened particle into a froth of tiny sealed cells. Bulk density can fall to as little as 30 kilograms per cubic metre.

By particle size distribution, since the size of the unexpanded ore determines the size and density of the expanded product. Fine ore gives fine expanded perlite suited to filter aids and horticultural media; coarser ore gives larger, lighter particles suited to insulation and lightweight construction. Expansion ratio and moisture are also specified.

Because it is inert, sterile, non-combustible and provides a highly porous cake with a large surface area and a complex tortuous path. That combination traps fine particles efficiently while allowing good flow rate, and because it is chemically inert it does not contaminate the filtrate, which matters in food, beverage and pharmaceutical filtration.