XRD characterization of cobalt-based historical pigments and glazes

This article covers the results of application of X-ray powder diffraction (XRD) in assessing the chemical and phase composition of historical pigments and their glazes. In order to demonstrate the reliability of the above technique, XRD analyses were performed on representative samples of the cobalt-based pigments and glazes. Ten individual pigments (Kremer Pigmente) were used for X-ray diffraction characterization: cobalt yellow, cobalt violet brilliant light, cobalt violet dark, cobalt cerulean blue, cobalt blue dark, cobalt blue light, cobalt blue greenish, cobalt green bluish, and two specimens of smalt with different grind. The same pigments, along with lead oxide (Pb3O4) and silica (SiO2), were used for the preparation of cobalt-based glazes. XRD analysis has proven to be a useful tool for the qualitative determination of the composition of glazes. However, in some cases many problems concerning the identification of separate phases are still to be solved using other analytical techniques.