BIOLOGICALLY INDUCED PATINA FOR METAL BUILT HERITAGE

Edith Joseph1,2, Pilar Junier1, Monica Albini1, Paola Letardi3, Emmanuelle Domon Beuret4, Laura Brambilla2, Lidia Mathys1, Christian Cevey4, Régis Bertholon2

1 Laboratory of microbiology, Rue Emile-Argand 11, 2000 Neuchatel, Switzerland, edith.joseph@unine.ch

2 Haute Ecole Arc Conservation-restauration, Espace de l’Europe 11, 2000 Neuchatel, Switzerland,

3 CNR Institute of Marine Sciences, Via de Marini 6, 16149 Genova, Italy

4 Archaeological park and museum Latenium, Espace Paul Vouga, 2068 Hauterive, Switzerland

ABSTRACT

The objective of this research is to propose an alternative biological treatment “Biopatina” for copper alloys’ surfaces. Based on the use of a specific fungal strain, soluble and/or active corrosion products are converted into more stable copper oxalates. Hence, thanks to copper oxalates’ insolubility and stability under acidic conditions, biopatina can stabilize the corrosion at long-term with low aesthetical effects on the treated surfaces. The performance of the newly developed treatment was evaluated in terms of compatibility, durability and impact on color.

The biopatina is currently proof-tested as artificial and aesthetical for contemporary art, architecture and built heritage. To this purpose artificially aged coupons were prepared and exposed in an urban environment. A similar set of coupons was treated with Cosmolloid H80 wax for comparison. The behaviors of biopatina and reference treatment are monitored since February 2014 and the total ageing procedure is foreseen over a 24-months period. In parallel, a dedicated delivery system was also developed and validated on outdoor sculptures and archaeological objects. The outdoor case studies will be presented here.

Parole chiave/Key-words: copper alloys, corrosion, fungi, biotechnology