1. Scientific Foundations Of Hollow Glass Microspheres 1.1 Composition and Microstructure one.1.1 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 typically incorporates silica (SiO₂, 50-90%), alumina (Al₂O₃, https://www.pearltrees.com/okok5/item753855454