Innovative techniques for the assessment of the degradation state of metallic artefact

Abstract

Summary: The degradation of archaeological metals is largely dependent on factors such as alloy composition, microstructure, and environmental conditions Commonly, these issues are targeted within specific disciplines such as materials science, archaeometry, conservation science, archaeometallurgy, and geoarchaeology. The topic could benefit from an integrated transdisciplinary approach, combining different techniques and methods. It is of importance to consider that artefact degradation not only relates to the general soil environment of the region, but can also depend on local variations in soil conditions within an archaeological site, and it is possible to have significant variations within the same artefact. Additionally, the conditions in an archaeological site are not a fixed stable situation; rather, environmental change can have a significant impact on the future preservation of artefacts in situ. This thesis applies several methodologies on a range of scales. First of all, a Roman site in Israel is considered, where anthropogenic factors are influencing the local soil conditions. Next, we assess intra-site sample variability through the use of non-invasive techniques to identify artefact groups within an Islamic site in Spain. In the following chapter, another Roman site, in Portugal, is studied through intra site-investigations into local soil conditions and corrosion products, by analysing a large number of soil and corrosion samples in combination with digital and statistical methods. Then, 3D recording and data visualisation techniques are applied to a Chalcolithic site in Israel. On a smaller scale of analysis, fragments from a single archaeological context from a Latin site in Italy are studied, to interpret the variation of different corrosion products in the same location. The next level is the investigation of artefact-scale variety in corrosion products and elemental composition of the surface, within a 3D framework. This is done on a Chalcolithic halberd from Portugal. A more detailed technique follows; micro-CT is used to assess microstructures and corrosion morphology of a variety of samples from different sites. Finally, future considerations into the changing environments are studied, by applying environmental models involving sea level change at a Phoenician site on Sardinia. Throughout the thesis, different scales are used to combine a selection of analytical techniques and approaches, such as SEM, XRD, XRF, photogrammetry, measurements of pH and conductivity, 2D and 3D GIS, and micro-CT. This work comprises of several transdisciplinary workflows, and might serve to improve and inspire future studies related to archaeological materials.