Castor Oil at Classe (Ravenna – Italy): Residue Analysis of some Late Roman Amphorae coming from the Port

During a fire at the end of the 5th century (about 490-500), among other buildings, a warehouse of the port of Classe was completely burnt. Inside there were different ceramic materials, such as lamps, amphorae, bowls and dishes, all coming from Africa, that remained in situ, thanks to the sudden event that destroyed the warehouse (building 17). The excavations were carried out during the years 2002 - 2005 by the University of Bologna and the Soprintendenza Archeologica of Emilia-Romagna. Among the amphorae recovered there were 200 Spatheia type 1 (Bonifay 2004, type 31) and about 180 wide cylindrical amphorae dated between the end of the 5th and the first quarter of the 6th century. In order to understand what these amphorae contained, chemical analysis of residues were carried out. Ten amphorae were selected to be analyzed (five spatheia and five cylindrical amphorae). All were sampled with a small drill and analyzed in collaboration between the Archaeometric Laboratory and the Centro di Analisi e Determinazioni Strutturali of the University of Siena with spot tests and gas chromatography - mass spectrometry. The results of the analyses were surprising: regardless the form of the amphorae, some of the spatheia and of the cylindrical amphorae contained castor oil, and only two amphorae showed the markers of a possible different vegetable oil. No fish traces were present in either type of amphorae, suggesting that these spatheia were not used to transport it. Furthermore, all the amphorae showed resin or pitch traces, although almost all of them contained oil. These data point out several problems on the attribution of a specific content to amphorae types, and on the presence of an organic coating in oil containers. Furthermore, the presence of castor oil is quite interesting, as it is one of the first times that it was identified in ancient materials.