Alteration of potash-lime silicate glass in atmospheric medium: study of mechanisms and kinetics using 18O and D isotopes

Abstract Only a few studies deals with the alteration of glass by water vapor. This study aims to investigate the mechanisms and to determine the kinetics of alteration of potash-lime silicate glass typical of the Middle Ages. For that, model glass samples were exposed to different conditions (relative humidity -RH-, temperatures) for several durations. The water vapor used in experiments was enriched in deuterium (D) and oxygen-18 (18O). Results show that mechanisms are highly temperature-dependent. At 50 °C, the alteration is driven by interdiffusion, whereas at 20 °C, the alteration is mainly governed by hydration without significant ion exchange. Then, the isotopic profiles of H, D, 18O and 16O show that after sorption of water molecules at the glass surface, the diffusing species in the glass matrix are mainly H+ or D+. Concerning the hydration kinetics, they evolve exponentially with time in the first stages of the alteration. Moreover, at 50 °C, the hydration follows a linear trend below 83% RH and strongly increases for higher RH values.