Non-destructive determination of the structure and composition of glazes by Raman spectroscopy

The utility of Raman spectroscopy as a non-destructive technique for the characterization of glassy (alumino)si licates (modern or ancient glazes and glasses) is demonstrated. The addition of fluxing ions breaks the Si-O linkages and the degree of (de)polymerization determines the relative intensity of the Si-O bending and stretching modes and hence the degree of polymerization could be classified. The analysis can be used to predict the processing temperature of glasses. Bending (Q '(n)) and stretching (Q(n)) spectral components assigned to isolated (Q(0) or SiO4), and more or less connected SiO4 vibrational units with one, two three/four bridging oxygen allow more precise analysis. The method is applied to reference modern porcelain glazes and selected ancient ceramic glazes and glasses, representative of the different production technologies used in the Asian, Islamic, and European worlds from Roman Empire to 19th century.