Ceramic experimental firing on clays for ceramic production in Umbria (Italy). Characterization of mineralogical transformations with temperature

• Experimental firing of clays collected in a Roman workshop with several kilns producing amphorae. • Compositional characterization of clays and amphorae mineral transformations with temperature. • Study of phyrotechnology and technological variations of raw material for amphorae production. Compositional characterization of ancient ceramics provides useful insights in the understanding of the technology of ceramic production as well as providing information on the temperature of kiln firing. This paper aims to identify the mineral behaviour of clays thermal transformations during firing in a kiln. Experimental firing, under controlled conditions, was performed to study the mineral behaviour of the same clays used for ancient ceramics to correlate heating rate and changes in mineral assemblages, according to the composition of the raw material. The study of phyrotechnology plays an important rule when the structures of ancient kiln, as well as raw material employed, are well known. Therefore, this contribution is based on the important key-study of six roman updraft kilns, discovered at Montelabate (Perugia. Italy), where clay pits were discovered. The results allowed a better understanding of the thermal transformations occurring during ceramic firing, taking into account the ancient potters’ technical choices of raw material, the potential errors incurred in kilns, estimating a temperature at around 900 °C, above when misfired, taking into consideration also post burial modifications.