Glass bubbles were developed in the 1960s as an outgrowth from the manufacture of solid glass beads. They are commercially manufactured by melting a unique glass formula that contains a latent blowing agent causing the molten glass particles to expand into a hollow bubble. The resultant glass bubbles are chemically stable, water resistant and compatible with many materials used for indirect food contact applications. The material technology has evolved in recent years to produce bubbles with a high strength to density ratio which enables their use in demanding polymer processing operations.