Characterization of the alteration processes of historical glasses on the seabed.

Glass objects are common in shipwrecks since they are associated with ordinary glassware or commercial products. The alteration pathologies of historical glasses from two wrecks from the Mediterranean Sea were analyzed to characterize their alteration mechanisms. The results of this research proved that the alteration layers presented a moderate content of Na 2 O, similar to the average salinity of the ocean, and a high content of Al 2 O 3 due to an extremely basic environment during the corrosion process. The biofouling layer protected the glass surfaces. Dark deposits with a high content of MnO were observed in the most instable glass. [ABSTRACT FROM AUTHOR]