Casting-on: Technical study of a unique hollow-cast copper vessel dated to the sixth dynasty using X-ray computerized tomography

Abstract

The article studied casting-on technique that was used to manufacture a hollow-cast vessel with a narrow neck. Casting-on technique, lost-wax addition, is casting a new part to attach with a pre-existing object whether cast or hammered. The case study is a small hollow-cast vessel dated back to the Sixth Dynasty [2465–2323 BCE]. It was excavated in Pepe-nefer mastaba at the Southern Upper Egypt, Edfu region. Non-invasive multi-detector computerized tomography (MDCT) and micro-analytical techniques (SEM-EDS, PXRD) were used to investigate the studied vessel. The metallographic microscope was used to examine the microstructure of both the pre-cast body and the casting-on part. SEM-EDS analysis was used to identify their elemental compositions. PXRD was used to analyze the brownish-red patina on the entire vessel’s outer surface. Also, PXRD was used to identify the chemical composition of the core material that inside the vessel. Axial, sagittal 2D CT slices and 3D CT reconstruction images revealed both the pre-cast body and the casting-on part were made by direct lost-wax casting technique. SEM-EDS analyses identified the chemical compositions of the pre-cast body and the casting-on part as copper-lead and copper-arsenic alloys respectively with a trace of iron in both. PXRD identified the cuprite with trace of copper as the chemical composition of the brownish-red patina that cover the entire vessel’s outer surface. The study proved that the casting-on technique was already practiced during the Sixth Dynasty as a metallurgical repair method for an imperfect pre-cast vessel. CT results helped to draw an ideational schematic representation for the casting process of both the two vessel’s parts. The study concluded that the studied vessel may be one of the early trails to manufacture the hollow-cast copper vessels during the Old kingdom.