Development of non-invasive and multi-technique analytical protocols applied to degraded metal artefacts

The proper characterisation of degraded metals is essential to determine their current condition and develop effective conservation and restoration interventions. The ability to obtain information about the original alloy of an artefact can be a breakthrough in identifying its period or place of production, providing valuable references. A groundbreaking doctoral study aims to establish diagnostic protocols utilising non-invasive, portable, cost-effective techniques that provide fast analysis and comprehensible data for copper-based artefacts. This study employs colorimetry, reflectance spectroscopy, and elemental analysis techniques to identify active corrosion, which is highly detrimental to artefacts. Moreover, it experiments with multivariate analysis methods and machine learning clustering and classification to make the most out of the vast number of analyses collected from real case studies from different collections. The results include the creation of datasets that hold hundreds of observations utilizing non-invasive techniques, which are partially examined by micro-invasive techniques that can identify the mineral phases present in the measurement areas. The study identifies the colorimetric space regions that are most affected by certain types of corrosion and defines the spectral reflectance characteristics of various mineral phases engaged 4 in corrosion products. It also demonstrates how the different techniques can provide valuable information and how adopting a multi-analytical approach can be useful in matching results. Lastly, the study develops a classification model to distinguish degraded Ptolemaic-era bronze coins, which can accurately predict the minting period of coins that are no longer legible and cannot be studied numismatically. This research provides a significant contribution to the field, paving the way for improved conservation and restoration interventions planning for copper-based artefacts.