A surface reaction in which ions in glass are replaced by different ions from a contacting liquid, commonly involving alkali ions in the glass and hydrogen-containing species from water.
GlassRenu · Educational illustration
Meaning and boundaries
Ion exchange is a chemical mechanism, not a visible defect category. It may occur before obvious haze, roughness, or mass loss appears.
Why it matters in glass restoration
The mechanism explains how water exposure can create an altered, silica-rich surface layer rather than merely leaving material on top of the glass.