Degradation of Traditional Silicate Glass and Protective Coatings Under Simulated Unsheltered Conditions

Outdoor glass is subject to degradation due to environmental factors, which alter its physical and chemical properties depending on the exposure conditions. Studying glass weathering and the effectiveness and durability of conservation treatments is necessary for developing optimal conservation strategies for glass heritage objects. Here, an accelerated aging protocol based on actual environmental data is successfully employed to replicate weathering caused by rain runoff, temperature, humidity and UVA radiation in unsheltered conditions. Two types of silicate glass with traditional compositions were artificially aged to investigate the corrosion processes and produce representative weathered substrates for applying and aging protective treatments. The performance of two recently marketed Siox-5 sol–gel systems was compared with that of Paraloid B72. Glass specimens, as well as leaching rain solutions, were analyzed with different techniques, including SEM/EDS, FTIR-ATR, color measurements and MP-AES. The composition of the glass influences weathering patterns, which in turn affect coating adhesion and overall performance. Sol–gel coatings demonstrate good chemical stability and tend to adhere more effectively to degraded surfaces than to well-preserved ones. The coatings exhibit varying degrees of sensitivity to environmental factors, with one of the sol–gel systems generally performing better than the others under the considered exposure conditions.