Characterization of bronze casting in Insula 56, in Roman Aventicum

Abstract

This study characterizes metallurgical wastes (slag) recovered from a bronze workshop during excavations in 1997-1998 at the Roman provincial city of Aventicum, located in western Switzerland, then Germania Superior. Previous research has identified the workshop as one devoted to the production of large leaded bronze statuary. The slag assemblage analyzed in this study is unusual due to the absence of ceramic crucible fragments normally associated with the production of copper alloys. Instead, this workshop is hypothesized to have used iron crucibles. Electron Microprobe Analysis (EMPA) and X-Ray Diffraction (XRD) were used to analyze the chemical composition of the slags in contrast to previous bulk analysis studies. Modern metal casting methods were observed for analogues. The data show that the slag reached temperatures between 1350°-1400° C and chemical components indicated the use of sand and lime fluxes. Evidence of high temperatures is proposed as one chemical fingerprint that can be used to re-assess slag for the presence of iron crucibles in other Roman bronze workshops.