Terahertz Spectroscopy Applied to Estimation of Firing Temperatures of Ancient Ceramics

We previously reported that the terahertz (THz) wave transmission of ceramics varies strongly with firing temperature. In this study, we propose a new method to accurately estimate the firing temperatures of ancient ceramic shards excavated from archaeological sites based on this dependency. THz time-domain spectroscopy (THz-TDS) was used to measure the THz wave transmission properties of ancient Arita porcelain and Banko pottery shards. Standard specimens were prepared from the raw materials used at the time of manufacture or currently available raw materials, and calibration curves of their THz wave transmission properties as a function of firing temperature were measured. The firing temperatures of the ancient Arita and Banko shards estimated from their calibration curves were 1241 ± 3 °C and 1141 ± 1 °C, respectively. These temperatures were within the firing temperature range estimated from X-ray diffraction analysis. Because the estimation method that we propose is based on a calibration curve, a narrower firing temperature estimation range is obtained. We consider our new approach to THz wave analysis to be a more accurate method for estimating the firing temperatures of ancient ceramics.