PRIMARY STABILIZATION FACTOR OF THE CORROSION OF HISTORICAL GLASSES -THE GEL LAYER

Leached gel layers of variable thickness and composition, mostly criss crossed by cracks and fissures, are built during long-term exposure of historical glasses. Depending on the glass composition as well as on the environmental conditions the gel layers show various shapes. They can be characterized by microprobe investigations, through photographs of the cross-sections in vertical plane to the corroded surface as we ll as determination of the chemical composition. Any cleaning measures in the course of restoration have to obey carefully their preservatio n, for it seems quite reasonable to assume that the progress of corros ion of the poorly resistant glasses is remarkably retarded by silica g el barriers.