Chemical and mineralogical characterization of Roman Sigillata moulds from Andújar (Jaén, Spain)

Abstract

Terra sigillata hispanica (TSH) was a Roman Imperial pottery easily recognized by its highly characteristic red surface. It was produced in several workshops in the Iberian Peninsula using moulds for decorated pieces. Seven of them were placed within the Baetica province. After > 40 years of systematic archaeological works, that of Andújar (Jaen) is the best known. Here, a full characterization of a series of 35 mould samples from this site is reported. The main employed techniques were stereomicroscopic examination, elemental analysis by X-ray fluorescence, Rietveld quantitative phase analysis from laboratory X-ray powder diffraction, including amorphous quantification by the innovative G-factor approach and, finally, scanning electron microscopy for microstructure characterization. Chemical data analysis allows the identification of two different clay sources. The mineralogical data show a wide range of variation in amorphous content (9–57 wt%). Firing conditions have been estimated (mostly using temperatures from 800 to 900 °C, clearly below those used for TSH production). The SEM study is in agreement with these estimations. These results will be used in the future for a broader comparison with the remaining, smaller Baetican workshops.