Study of historical lead silicate glasses and their preservation by silica coating

In the last years the interest for protection of the historical objects has increased. Among them a high number of ancient and middle age objects were made from lead silicate glasses. Such historical objects from glass contain small quantities (below 5 wt%) of transitional elements as Cu, Ag, Fe, which decrease their resistance at weathering. Previous investigations show that protective sol-gel silica coating does not change the appearance of artistic alkali silicate glasses when it is deposited on their surface. In the present paper model lead silicate glasses with compositions similar to ancient objects were studied. Their chemical resistance in water, morphology and structure was investigated, being established that the iron added into glass changed the corrosion mechanism. In order to prevent the weathering of the synthesized glasses, a protective thin film was applied on surface. All glasses show a better resistance at water attack after coating with a film of silica gel.