Surface Modification Processes on European Union Bronze Reference Materials for Analytical Studies of Cultural Artefacts

Abstract

This paper presents research results obtained in the 4th Framework Programme (1994–1998) of the Standards, Measurements, and Testing Programme of the European Union, DG XII: ‘Improvement of means of measurements on archaeological copper alloys for characterisation and conservation’ (IMMACO) project. One of the aims of this project was to study copper alloy compositions of European objects dating from the Bronze Age to Roman times. This work has revealed that five types of alloy seem to be particularly representative of what was produced in Europe during this period. These alloy compositions will be certified as reference materials by the European Union. In the second part, artificial patinas have been made on the different bronze alloys using electrochemical polarisation as the surface modification technique. The characterisation of the corrosion surfaces and interfaces formed during the treatment with light microscopy and scanning electron microscopy (SEM-EDX, X-ray mapping) have shown that the artificial patinas seem to be very close to those from excavations. As a consequence the patinated specimens can be used as a substitute for genuine artefacts in the future to improve conservation techniques.