LARGE SCALE INVESTIGATION OF BRONZE ARCHEOLOGICAL ARTEFACTS FROM MEDITERRANEAN BASIN

In the framework of the EFESTUS project financially supported by the European Commission (INCOMED contract No. ICA3-CT-2002-10030) and aimed to find tailored strategies for the conservation of archaeological value bronze artefacts from Mediterranean Countries, well-defined groups of Cu-based alloys archaeological objects have been selected as a function of the archaeological context, of the degradation state and of the expected chemical composition and structure. The archaeological artefacts have been studied by means of the combined use of different analytical techniques such as SEM-EDS, XRD, OM, GDOES, XPS, ICP-MS, AAS, DTA-TG, XRF and XPS. The results indicate that their chemical composition is very wide and includes all kinds of the ancient Cu-base alloys such as copper, low tin and high tin also leaded materials and that the artefacts have been subjected to different degradation mechanisms. In order to find a relationship between burial condition and degradation mechanisms, also the archaeological soils have been studied and the different corroding agents identified. Furthermore, in order to ensure a long-term and stable life to the archaeological bronze artefacts the storage and exhibition atmosphere of 8 important Mediterranean Museums have been monitored by using a purposely-developed strategy and equipments that have been used for determining the environmental key parameters affecting the long-term stability of artefacts during exhibition or storage in the Museum. Finally, a wide series of reference Cu-base alloys not commercially available and whose chemical composition, micro-chemical structure and metallurgical features are similar to those of ancient alloys has been produced. These reference Cu-base alloys have been used to test the effectiveness of new low toxic materials for the reliable and long-term conservation of archaeological bronze objects.