1. Scientific Foundations Of Hollow Glass Microspheres one.1 Composition and Microstructure 1.one.one Chemical Composition: Borosilicate Dominance Hollow glass microspheres (HGMs) are mainly made up of borosilicate glass, a material renowned for its very low thermal expansion coefficient and chemical inertness. The chemical makeup usually features silica (SiO₂, 50-90%), alumina (Al₂O₃, https://demo.jcow.net/images/viewstory/88300