The production and technology of glazed ceramics from the Middle Ages, found in the Saepinum territory (Italy):: A multimethodic approach

A collection of ceramics from the Middle Ages found in Altilia and Terravecchia (the Saepinum area. Campobasso, Italy) were characterized by using different mineralogical analyses to investigate their provenance and production techniques. The body ceramic was investigated using Rietveld phase analysis of X-ray powder diffraction patterns, X-ray fluorescence spectrometry and scanning electron microscopy. The chemical compositions of the coatings were measured by scanning electron microscopy and their mineralogical compositions were determined using a particular technique of X-ray small-angle scattering (SAS) optimized for studies of thin films. Moreover, the material used for decoration was studied using micro-Raman spectroscopy. The archaeometric results confirmed the distinction into two different ceramic classes, already individuated front archaeological analysis: the Altilia objects belong to the protomajolica class, whereas the objects from Terravecchia are RMR (ramina-manganese-red) ceramics. A comparison between the chemical and mineralogical compositions of good-quality ceramic objects and those of waste products indicated local production of the ceramics. A sharp distinction was found in the chemical composition of the coatings: the Altilia products have tin-opacified lead glazes, while the Terravecchia ones have transparent high-lead glazes. Among the Altilia products, the unsuccessful process that produced a large quantity of discarded materials was attributed to the high lead content of the glazes. In fact. the principal advantage of the high lead content was to make the preparation and application of the glaze suspension easier, but the risk of reduction of lead oxide to metallic lead was greatly increased. Using micro-Raman spectroscopy, the following minerals were identified as pigments: pyrolusite for the dark colour, malachite for green, lepidocrocite for yellow and hematite for red.