May 16, 2021 · Composition of glass. Glass is principally made up of silica (59-80%) with varying degree of calcium oxide (5-12 %) sodium oxide (12-17 %) aluminium oxide (0.5-3.0 %), barium oxide, boric oxide, potassium oxide, and magnesium oxide. The high melting point of glass is due to the presence of silica. The melting point and melt viscosity of the