NATURE AND MICROSTRUCTURE OF GALLIC IMITATIONS OF SIGILLATA SLIPS FROM THE LA GRAUFESENQUE WORKSHOP*

The red glaze (slip) that characterizes the Terra Sigillata potteries greatly contributed to their success during the Roman period. The colour of the slip can in fact be partially explained by the microstructure (crystalline phases, grain sizes) and the physico-chemistry (composition) of the ceramics. However, the precise process and the diffusion of this technique are still not fully known. In particular, we do not know yet how the production of sigillata took place in the south of Gaul, and the role that was played by the production under Italian influence (pre-sigillata) preceding the first local sigillata. In this work, a combination of transmission electron microscopy (TEM) and X-ray synchrotron diffraction techniques was used to study the microstructure of pre-sigillata slips from the main southern Gaul workshop (La Graufesenque), in order to compare their characteristics with those of high-quality sigillata. These first results seem to indicate that the antique potters chose clays adapted to their firing conditions and to the type of coating that they wanted to make. These productions cannot be described as an initial phase for the later sigillata production and, rather, seem to correspond to the intention of developing a specific type of pottery only inspired by the famous Italian sigillata forms.