Sol–Gel Thin Films for the Protection of Ancient Glass Artifacts: A Performance Comparison Between Inorganic and Hybrid Silica Compositions

The preservation of archaeological and historical glass requires advanced conservation strategies. While some existing methods are effective in some instances, they often have limitations, such as the need for high-temperature densification treatments or undesirable interactions with the glass substrate. This study investigates the development of sol–gel-based protective coatings for glass, focusing on both inorganic and hybrid formulations. The main aim is to formulate silica sol–gel solutions catalyzed with low acid concentrations and applied at room temperature, reducing the risks associated with conventional methods while enhancing the long-term preservation of ancient artifacts. Silica-based coatings are synthesized using three silica precursors–one fully inorganic and two containing organic alkyl groups of different lengths–along with variations in the molar ratio of precursors, water and ethanol. These formulations are applied to soda-lime glass substrates via dip coating, forming thin films between 100 and 150 nm. The coated samples undergo multiscale analysis, including accelerated ageing tests to simulate environmental degradation. Results demonstrate that hybrid coatings functionalized with methyl and octyl groups provide superior barriers against the diffusion of alkaline and alkaline-earth elements, outperforming purely inorganic coatings. This research highlights the potential of hybrid sol–gel coatings as effective and durable protective solutions for glass conservation.