A multi-analytical investigation on medieval pottery from Caltagirone (Sicily-Italy)

A multi-analytical approach was used to investigate Medieval and post-medieval (thirteenth-seventeenth century) ceramic artefacts from archaeological excavations at Caltagirone (Sicily, Italy). The chemical, structural and micro-morphological characterizations were carried out by the combined use of surfacesensitive techniques, such as X-ray photoelectron spectroscopy (XPS), and bulk analytical techniques, such as scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD). Fragments of basins, bowls, vases of great historical and archaeological interest as the first Sicilian evidences of such polychromatic decorations were sampled in different conservation conditions. In order to characterize the conservation state and determine the possible causes of alteration and/or degradation phenomena, for each sample both the ceramic body and the polychromatic glaze of the artefacts were studied. The presence on some artefacts of a lead glaze, which is typical of Islamic ceramics, suggested the use of manufacturing techniques directly derived from the Islamic domination in Sicily, even beyond the ninth century. Degradation phenomena such as the partial devitrification of the glaze, i.e. the slow structural reorganization towards stable crystalline phases, and the leaching by mineral dissolution in the soil, were determined by surface and bulk analysis results.