Hybrid sol-gel based protective coatings for historical window glasses.

Medieval glass is generally attacked by atmospheric pollutants conveyed by water in liquid or vapor form, which activates the corrosion process. Since the conservation strategies are currently addressed to maintain the windows in their original contexts, it is necessary to protect them from further degradation phenomena. We report here on the results of water-repellent hybrid sol-gel coatings obtained by using tetraethyl orthosilicate (TEOS) mixed with different amounts of Si-alkoxides functionalized with alkyl groups. Static contact angle measurements were performed to check the water-repellency of the surfaces. On the basis of the transparency, the contact angle values and the lowest amount of the organic component, three compositions were selected and applied on medieval-like glass samples that were colorimetrically characterized. The silica-based protective materials don’t lead to reaction by-products, are water-repellent, compatible with the glassy substrate, colorless and transparent, hence satisfy the main requirements of the conservation of Cultural Heritage.