Microchemical characterisation of Hispano-Moresque and Umbrian lustre-painted pottery

Hispano-Moresque and Umbrian lustre-painted pottery, manufactured from thirteen to fifteenth centuries, has been found during archaeological excavations at Siracusa (southern Italy) and at Formello (central Italy). By means of scanning electro (SEM+EDS), optical microscopy (OM) and X-ray diffraction (XRD), the ceramic body and the surface decoration layer of these materials has been studied. The first microchemical results indicate on the outermost layer of the gold-like lustre-painted surfaces, the presence of a complex microchemical structure constituted by small rounded particles of silver metal mixed with silver oxide, whose size ranges from 0.1 micron to 1 micron. These particles are responsible from the specular and diffuse reflection of the light even thought they are not uniformly distributed on the surface of the lead silicate coating where cassiterite (SnO2) and quartz crystals are also present. Furthermore, the results obtained from the reddish copper lustre, show the occurrence of the above described structure whit the presence also of copper and Cu (I) oxide particles.