Environmental degradation of Modern non-balanced glasses

Abstract

Crizzling is an alteration pathology related to non-balanced glasses (high content of flux oxides and low content of stabilizer ones), which can produce an intense damage such as transparency losses, appearance of drops on the surface or cracking. In this study two case studies (outdoor and indoor environment) were presented. The main alteration agent for these glasses was the water (rain, condensation and environmental humidity). In the outdoor environment, the rain washed away the [OH−] ions formed during the alteration; however, the exposure to cyclic conditions accelerated its alteration rate. In the indoor environment, early stages revealed to consist of an alkali leaching that concentrates on the surface, on specific areas, that were related to water adsorption and consistent with the weeping phenomenon. Cracking and flaking of the surface represents a later stage, occurring specifically in unbalanced compositions.