Terahertz Characterization of Roman Amphora Sherds

Abstract

Amphorae frequently have a whitish skin that has been mistaken for a slip or painted layer over the otherwise pinkish ceramic. This skin is due to the simultaneous presence of calcite and NaCl in the clay, leading to depletion of red iron oxides near the surface. We demonstrate that terahertz time-of-flight tomography can provide a nondestructive, contactless means to measure the skin thickness on amphora sherds, finding a thickness of ~50 μm.