The first unusual spots have appeared on the faces, legs and abdomen of the Riace Bronzes and experts say that more frequent check-ups are needed to ward off "cancer".
The two Greek bronzes of naked, bearded warriors from around 460-450 BC were found in the sea near Riace in 1972. They are currently held at the Museo Nazionale della Magna Graecia in the southern Italian city of Reggio Calabria, Italy.
Experts from the University of Salento and the Istituto Superiore per la Conservazione e il Restauro (ISCR) in Rome made the announcement at the National Archaeological Museum of Reggio Calabria as part of the initiative 'Arte E' Scienza', held over the weekend in several Italian cities by the Associazione Italiana di Archeometria (AIAr) to illustrate the most advanced techniques of scientific investigations applied to culture.
One example is fluorescent X-rays, a non-invasive diagnostic technique used by the "doctors" in charge of the bronzes to examine them "lying down" in a sort of "field hospital" set up in Palazzo della Regione Calabria. Researchers were able to analyze the chemical composition of the patina left on the lower part of the two statues and create a sort of map of the spots which will serve to draw up future "cancer prevention" strategies.
"On both of the bronzes," said Giovanni Buccolieri, applied physics researcher at the University of Salento, "we found several places that were covered in a blue patina created by chloride residue left by the long period in the sea. Under certain temperatures and humidity, these spots could spread with the risk of forming a sort of 'bronze cancer', a corrosive phenomenon that would damage the conservation of the statues."
To prevent this, the patina should be removed - similar to what is done to birthmarks on patients at risk of melanoma. Any intervention, however, would be somewhat invasive and "thus for the moment", the researcher said, "we can just monitor the evolution of the situation with more frequent check-ups."
The analyses brought to light two other surface patinas: a reddish one created by the natural oxidation of copper contained in the alloy, and a black multi-layered one that is compact and smooth, made of copper sulfate.
"The latter was probably protective wrapping for the statues," Buccolieri said. "The patina is still clearly visible on Bronze A ('The Young Man'), while it has been partially removed from Bronze B ('The Old Man') due to restoration done in Florence in the 1970s."
The invasiveness of the intervention is also shown by the zinc residue on the "skin" of the warrior, which "was probably left by brass brushes used during the cleaning of the statue", he added.
Source: ANSA [December 08, 2016]