One. Scientific Foundations of Hollow Glass Microspheres one.1 Composition and Microstructure one.one.1 Chemical Composition: Borosilicate Dominance Hollow glass microspheres (HGMs) are primarily made up of borosilicate glass, a material renowned for its very low thermal expansion coefficient and chemical inertness. The chemical makeup typically incorporates silica (SiO₂, 50-90%), alu... http://www.mysportsgo.com/profile/okok0972/action_id/1516637/show_comments/1