During the 18-19th century the colour palette of the Portuguese ceramics was characterized by the use of yellow, orange, green and blue colours. In tin opacified lead-alkali glazes, such as the glazes used in the majolica technique, the yellow colour can be obtained by Sb-Pb or Sb-Sn-Pb pigments. This is the case of antimony-containing pyrochlore-type double oxides such as bindheimite, a yellow pigment with approximate formulae Pb2Sb2O7. Other colours such as orange, grey and green are a mixture of the yellow pigment with iron or cobalt.

To ascertain antimony speciation and to better understand pigment incorporation in ancient glazes it is necessary to study both antimony and lead speciation in the glaze. Accordingly, the XAFS characterization of both Sb K-edge and Pb L-edge is the optimal methodology. Samples analysed are unique majolica-type polychrome from 18-19th century Portuguese manufacture and Portuguese tiles and faience objects from Portuguese Factories (Bandeira, Estremoz and Fervença). Here reported are the first results on XANES analysis for the clarification of the structural role of Sb and Pb in the glazes for comparison with results from 17th century tile glazes. The detailed structure of an absorption edge (XANES) is the answer on information on the bonding state and speciation of an element responding also to the geometry of the atomic environment. XANES has been successfully applied to this type of studies for other type of tile glazes and glasses being the answer to questions of this specific majolica-type glazes [1-6].

References

M.L. Coutinho, J.P. Veiga, L.C. Alves, J. Mirão, L. Dias, A.M. Lima, V. S. Muralha, M. F. Macedo (2016) Characterization of the glaze and in-glaze pigments of the 19th century relief tiles from the Pena National Palace, Sintra, Portugal. In Press Applied Physics A.

M.L. Coutinho, V.S.F. Muralha, J. Mirão, J.P. Veiga (2014) Non-destructive characterization of oriental porcelain glazes and blue underglaze pigments using µ-EDXRF, µ-Raman and VP-SEM. Applied Physics A, 114, 695-703.

M.O. Figueiredo, J.P. Veiga, T.P. Silva, J.P. Mirão, S. Pascarelli (2005) Chemistry versus phase constitution of yellow ancient tile glazes: A non-destructive insight through XAS, Nuclear Instruments and Methods in Physics Research B, 238 (1–4), 134-137.

M.O. Figueiredo, T.P. Silva, J.P. Veiga (2006) A XANES study of the structural role of lead in glazes from decorated tiles, XVI to XVIII century manufacture. Appl. Phys. A 83, 209–211..