Exploring the raw materials and technological practice to obtain red and black surfaces of Apulian red figure pottery by Raman and SEM‐EDS investigations

In this paper, 4th century BC Apulian red vases, from sites among the most relevant in Apulia (Italy), are studied by means of Raman spectroscopy. The effectiveness of this technique in the archaeometric research is emphasized, particularly regarding the manufacturing procedures and raw materials of black and red surfaces. Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDS) analyses are carried out jointly with Raman spectroscopy in order to complete the morphological and chemical information. The results show that two different clays have been employed for black gloss and ceramic body. The black gloss proves composed of the finest fraction of terre rosse—very common all over Apulia—with no organic material added to its clayey suspension. Traces of carbon found on the surfaces can be ascribed to fly ash deposited during the firing process. This research highlights that two more methods besides red engobe were used by Apulian potters to color red the surface of whitish/grayish vases realized with local raw materials, namely, the addition of either “miltos” or a clayey layer enriched in Fe oxides. A multistep firing (ox-red-ox), reaching the maximum temperature of about 900C, can be deduced from the different mineralogical phases identified through Raman. The possibility of gaining information on the hematite particles size from the position of its characteristic Raman bands is successfully investigated, allowing to get clues on the presence of a surface layer in a nondestructive manner by comparing the particle size there and in the ceramic body.