A multitechnique study of archaeological bronzes: Part II

This study is a sequel to an earlier paper (shown as Ref. 6) recently offered by us, and is concerned with two tin bronzes (denoted as samples A and B) dating from the 9th century BC. We used XPS, synchrotron radiation-induced total electron yield X-ray absorption spectroscopy (XAS), synchrotron radiation-induced photoelectron microscopy (PEM), electron-probe microanalysis (EPMA), and optical microscopy metallographic techniques to explore the elemental and microchemical properties of the two bronzes. The combination of these analytical methods allows us to explore the surface layers and the bulk regions of the two samples, and major interest is to study their chemistry and microstructural properties. We find that the surface is the region in which the most noteworthy differences between the two bronzes occur. The oxidation extent of the copper is distinctly higher for sample B than for sample A, and XAS highlights such difference with a detail which is higher than that provided by XPS. EPMA reveals the enrichment of cobalt species and lead species in the bulk of sample B and sample A, respectively, as well as that the enrichment of the lead species is locally inhomogeneous. PEM analysis highlights the lateral inhomogeneity of lead species at the surface of sample A with a spatial resolution of <0.5 µm. We discuss the results emerged from our study in the light of the diagnostic potential of each technique in terms of elemental sensitivity, chemical-state mapping, surface sensitivity and spatial resolution, and conclude that they can be useful to appreciate the archaeological importance of the two bronzes.