The study of pitch via gas chromatography-mass spectrometry and Fourier-transformed infrared spectroscopy: The case of the Roman amphoras from Monte Poro, Calabria (Italy)

The analysis of the composition of organic residues present in ancient pottery are an important source of information for archaeologists. The chemical characterisation of these materials gives information on diets, habits, technologies and original use of the vessels. In this paper the resinous materials from the interior surfaces of Roman amphoras and the contents of two particular vessels (called Kadoi) coming from Monte Poro, in Calabria (Italy) were studied. The organic materials were identified by Fourier-transformed infrared spectroscopy (FT-IR) and gas chromatography coupled with mass spectrometry (GC–MS). The presence of monocarboxylic acids and terpenic species shows that the organic residues were of vegetable origin or mainly consist of vegetable-based resins. Moreover, the presence of characteristic diterpenic biomarkers permits to recognize the use of pine resin and pine pitch, while the presence of methyl dehydro-abietic acid is likely linked to the use of wood tar and not only to the pine pitch. It was not possible to identify with accuracy the species of Pine used to prepare the pitch since the profile of diterpenoid acids of an aged and thermal treated resin is very different from the one of fresh resin. Nevertheless, the hypothesis about the use of Pinus Laricius and Pinus Negrus to prepare the pitch is plausible as these two species were and are both very abundant in Monte Poro's area.