Artefacts from Ban Chiang, Thailand: pottery with hematite-red geometric patterns

Abstract

Abstract Ban Chiang () is an extensively studied archeological site in Northeast Thailand, Udon Thani Province, which became a UNESCO world heritage in 1992. Depending on their production period ceramic artefacts show characteristic patterns at the surface which may be interpreted as iconographic motifs for the site. Two ceramic samples, excavated in 2003, from different periods were re-investigated, previously studied by Tanthanuch W., Pattanasiriwisawa W., Somphon W., Srilomsak S. Synchrotron studies of Ban Chiang ancient pottery. Suranaree J. Sci Technol. 2011, 18, 15–28 who focussed on thermal firing and redox-conditions. Shards selected for this study were sample 5412-S6E15 dated from Bronze Age (ca. 1000–300 BC) with yellow-brown, paint-free surface and a younger sample 8027 from Iron Age (ca. 300 BC–200 AD) with red painted design carrying pictorial patterns typical for the Ban Chiang ceramics. The surface material and colour of both shards was studied in detail using optical reflectance, FTIR spectroscopy and X-ray powder diffraction. Thin sections were used to determine the thickness of the red paint and the elemental composition of the surface using an electron microprobe. Chemical composition of sample 5412-S6E15 consists as oxides of elements mainly of SiO2 and Al2O3 (representing ca. 59 and 20 wt. %) and that of the red colour of the youngest sample 8027 consists mainly of SiO2, Al2O3 and Fe2O3 (representing ca. 52, 13 and 13 wt. %), the average composition adjacent to the red painted area has ca. 72 wt. % SiO2, ca. 10 wt. % Al2O3 and only 2 wt. % Fe2O3. X-ray powder diffraction, FTIR spectroscopy and optical reflectance measurements confirm hematite in the mineralogical composition of the red pigment of shard 8027.