The nature of the corrosion products present on the surface of artistic and
archaeological metal artefacts is intrinsically related to the environmental context
(atmospheric or burial). In order to effectively protect and inhibit the corrosion of such
metal objects, the practices adopted should take into account the nature of the patina
and its corrosion behaviour. However, the treatments so far employed are organic
protective coatings, which do not consider the difference in terms of patina composition
and corrosion products stability and simply create a barrier against aggressive
environments in a non-selective way. A multidisciplinary project BAHAMAS is here
proposed for developing an alternative biological treatment as a novel approach for the
conservation-restoration of metal artefacts.
The research activity aims at chemically and specifically modifying existing corrosion
products into more stable and less soluble compounds while maintaining the surface’s
physical appearance. Some species of fungi have been already reported for their ability
to transform metal compounds into metal oxalates, which are known to be insoluble and
high protective compounds towards corrosion. Thus, the participants will exploit this
potential for the transformation of existing corrosion patinas into metal oxalates. Some
promising results have been obtained after a first attempt on bronze standards with
copper hydroxysulphates and copper hydroxychlorides patinas. The research work will
investigate the formation mechanisms and adhesion properties of the newly formed
metal oxalates on different metal substrates (copper, iron and silver), which are
frequently found in cultural heritage artworks. The collaboration between the Swiss
National Museums, the University of Neuchâtel and the researcher will allow the creation
of a unique interdisciplinary team and will represent a key aspect for the accomplishment
of this innovative research issue in the field of conservation science.