Characterization of archaeological glasses by micro-Raman spectroscopy

The method based on the deconvolution of the Raman spectra of glasses, proposed for the investigation of glazed ceramics by Colomban, is applied to archeological samples of glass of two different origins in an attempt to characterize the glass composition and the fictive temperature using a contactless, nondestructive spectroscopic technique. The samples investigated are glassy mosaic tesserae of Roman times from Massa Lubrense, Napoli, Italy, and medieval rosary grains found during the excavations in the church of San Martino di Rivosecco, Parma, Italy. The polymerization index, obtained as the ratio of the bending and stretching band amplitudes, suggests firing temperatures not less than 1000–1100 ◦C for both Roman and medieval glasses. From the wavenumber shift of some stretching bands at about 1050–1100 cm−1, the content of lead was estimated. The medieval samples show a lower Pb content, a result confirmed by elementary energy dispersive X-ray spectral data.