Technological and provenance study of renaissance earthenware fron Aosta (Italy)

Some archaeological investigations, promoted by Regione Autonoma Valle d’Aosta, Assesorato alla Cultura and Servizio Beni Archeologici, have been carried out in 2005, just in front of the Aosta Cathedral. The excavation revealed the workshop and the kiln where architectural earthenware, used for the Cathedral façade decoration, were produced and fired. The construction of the new Cathedral façade was started in the second half of XV century and finished in 1526. The polychrome earthenware Renaissance Apostle statues are located in the arch entrance which is decorated with flowers tiles. Flower tile sherds, clay mixtures, raw clay bricks and firing scraps have been found in the excavation. These findings suggest that only the tiles for the Cathedral decoration were fired in the kiln, as scraps from the sculptures weren’t excavated and the small size of the kiln suggests that the statues were made in another workshop. Evidences from the clay materials suggest two possible provenances: a local deposit, probably known by Romans, and/or a deposit in the Eporediese (Ivrea region). In this work the manufacture process and the firing conditions are reconstructed through the petrological and mineralogical study of the archaeological findings. Thin sections of tile sherds have been studied to determine their textures and components. Moreover firing tests have been run on mixtures obtained using the original clay materials from the excavation in order to locate the clay provenance area and to compare them with the actual tiles and to reconstruct the technological features of the craftmen. The observation under polarizing light optical microscope allow to correlate the clay mixtures with the scraps. The yellowish clay found in the excavation has been fired at 850°C and compared with three tiles fragments found in the same spot. The fired yellow clay mixture is texturally characterised by alternating bands consisting of layers with a high temper percentage content and layers with high percentage of matrix. The same texture is observed in the tile sherds from the excavation, supporting that tiles were produced using these raw materials. Future development of this work is the examination of the clays, tiles, scarps and mixture firing tests by Scanning Electron Microscopy (SEM) and X-Ray Fluorescence.