Glasses on the seabed: surface study of chemical corrosion in sunken Roman glasses

The current work aims to describe surface weathering of ancient glasses in marine environment. All data are collected using dif- 11 ferent techniques: optical microscopy, RGA, surface techniques (XPS, SEM and SIMS). Three types of glass weathering have been 12 observed: white glass, glossy glass and glass showing growth rings. A compact structure characterizes white glasses, while a porous 13 structure with flaked layers is typical of glossy glasses. White glasses show different abundance of characteristic elements or mole- 14 cules (Mg(II), Sb(V), Ti(IV) and micro-crystalline silica). Glossy glasses, instead, are characterized by peeling layers of nearly pure 15 silica glass, with small differences in composition owing to ionic mobility phenomena. Data suggest a time relation between white 16 and glossy glasses. Visible growth rings characterize the third class of glass. They are made of titanium and antimony compounds 17 centers surrounded by many rings with the same composition. Their temporal evolution has been explained according to the theory 18 of Liesegang rings. Hypotheses on antimony and titanium origins are reported.