Efficacy of zinc salts to protect glass against atmospheric alteration. Part I: Effects of a spraying treatment

Following an industrial process to protect manufactured glass windows against atmospheric corrosion during their storage and transport, this research is focused on the possibility that a surface deposit of a small amount of zinc salts may efficiently reduce the atmospheric alteration kinetics of ancient glasses (soda, potash, and mixed alkali silicates). To this end, the chemical action of zinc salts was investigated by means of aging experiments (with temperature and relative humidity (RH) control) on three glass models, of which compositions are representative of the cultural heritage. When the treatment was performed on pristine glass (about 1 mu g/cm(2) of deposited Zn2+ ions), treated glass plates developed a significantly thinner hydrated layer than the untreated ones at 80 degrees C or at 40 degrees C (85 RH%). The formation of alkali and Ca-carbonates salts on the surface was also considerably reduced. The state of the glass surface undergoing the Zn treatment and the temperature of the treatment seem critical regarding the efficacy of the protection.