Della Robbia blue glaze: micro-Raman temperature study and X-ray fluorescence spectroscopy characterization

Micro-Raman temperature study and X-ray fluorescence (XRF) spectroscopy were used for characterization of the blue glaze on Saint John the Baptist - majolica terracotta relief attributed to Andrea Della Robbia and Saint John the Baptist with Cross - majolica terracotta statue attributed to Giovanni Della Robbia. Both objects are on permanent exhibition in the John and Mable Ringling Museum of Art in Sarasota, FL. This study proves that the detection of the 548 cm(-1) Raman band alone cannot serve as evidence for presence of lazurite crystallites in the pigment in the glaze. It was established that the famous Della Robbia blue is due to the combined effect of Co-Ni-Cu-Zn atoms and S(3)(-) ions embedded in a lead silicate matrix. It is proposed that the Della Robbia family used Co-containing sulfide ores as a source for manufacturing their blue pigments. Copyright (C) 2009 John Wiley & Sons, Ltd.