Polymerization degree and Raman identification of ancient glasses used for jewelry, ceramic enamels and mosaics

We demonstrate the utility of Raman spectroscopy as a technique for the identification of ancient glasses and enamel coatings of ceramics. As for any silicate glasses, the addition of network modifiers breaks the Si–O linkages and modifies the degree of polymerization and hence the relative intensity of the Si–O bending and stretching modes. We demonstrate empirically that the ratio of these envelopes is well correlated to the glass structure and to the firing technology used. Spectral Qn components assigned to isolated and connected SiO4 vibrational units allow more precise analysis. Selected porcelains, faiences, potteries and glasses representative of the different Asian, Islamic and European production technologies were studied. Modern porcelain enamels are used as compositional references.