Britannica Sources used in this answer

How does adding alkali ions affect the viscosity of molten silicate glass?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Observe how a superhydrophobic multifunctional glass surface resists fogging, glare, and self cleans — industrial glass Examining a superhydrophobic glass surface that resists fog and glare and is self-cleaning.

In molten silicate glass, the addition of alkali ions—which act as network-modifying (NWM) ions—leads to a decrease in viscosity.1

This occurs because the silicate structure is composed of a three-dimensional network of SiO₄ tetrahedra connected at their corners by bridging oxygen atoms. When alkali ions are introduced, they break these connections by creating nonbridging oxygen atoms, where the oxygen is joined to only one silicon atom. This process reduces the overall connectivity of the glass network. Because the viscosity of silicate glass is fundamentally tied to the strength and connectivity of this tetrahedral network, the structural breakdown caused by the alkali ions results in a lower viscosity. Additionally, increasing the concentration of these alkali additions lowers the glass transition temperature (T_g).213