Glass is an inorganic mixture

Glass is the inorganic mixture fused at high temperature which solidifies on cooling but does not crystallize. It’s basic components, network formers and modifiers are present in the form of oxides in ordinary glasses.

Typical glass formers (network formers) are silica (SiO₂), boric acid (B₂O₃), Phospharic acid (P₂O₅) and, under certain circumstances, also aluminum oxide (Al₂O₃). These substances are capable of absorbing (dissolving) certain amount of metal oxide without losing their glassy character.

This means that the incorporated oxides do not particpipate as glass formers but modify certain physical properties of the glass structure as “Network modifiers”.