Electron backscatter diffraction (EBSD): a new technique for the identification of raw materials and pigments in ancient glasses and ceramics

Coloured samples of glass and ceramic were selected for EBSD investigation to verify the potential (advantages and limitations) of this technique in the characterization of the raw materials used and the neoformation phases originating from the manufacturing processes. In the case of copper-bearing red glasses, it was verified that micrometric droplets, residuals of the original copper source, can be ascribed to metallic copper or to a low-Sn bronze, due to strongly similar lattice parameters. From the same samples, micrometric flakes were identified by EBSD as magnetite and interpreted as residues of the reducing agent used in the production of such red glasses. Further, the technique allowed the pigment responsible for the yellow colouring of some incised slipware to be recognized as bindheimite. In a third case, the black pigment, contained in some Nestorian decorated pottery, was identified as an amorphous phase of Mn oxide. The accurate identification of the colouring particles and other products or materials offered a more precise comprehension of the production technique, period and site of the examined artefacts, together with scientific parameters for the identification of the raw materials, their transformation during the production cycle and an evaluation of the most reliable recipes used for their preparation.