Application of computed tomography in the analysis of glass beads unearthed in Shanpula cemetery (Khotan), Xinjiang Uyghur Autonomous Region

The glass beads unearthed in sites along the Silk Road usually indicate the communications of arts, business, and cultures between different areas. The production process of glass beads also implies an associated local culture, as well as its provenance. Computed tomography (CT) is a non-destructive three-dimensional method and it has been widely used in the research of various relics. It contributes to discovering and documenting the manufacturing processes for artifacts. Based on the CT images of two glass beads which were unearthed in Khotan, Xinjiang, China, the inner structure and air bubble shapes were investigated. This paper demonstrates how the CT technology contributes to studying the manufacture of archaeological glass beads. Two polychrome beads were analyzed by CT scanning techniques. Bead S-2 is a typical natron glass and bead SC-8 is a soda-lime-silica glass, based on the chemical components analyzed by laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES). According to computed tomographic analysis, a porous core was covered with a thick layer of glaze. The eye parts from S-2 eye bead were probably made by an embedding technique, which was proved by the 3D shapes of bubbles and the “eyes.” The SC-8 bead was manufactured by a stretching technique which was evidenced by the elliptical bubbles. The yellow stripes wrapped around the glass base present sharp edges in cross section, which seem to reflect grooves carved before the filling process.