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Laboratoire Valectra d'EDF R&D
Cutting-edge techniques identifying the microstructures in an object help curators, restorers and historians improve their knowledge of works of art and archaeological remains. EDF engineers have recently applied the replicas technique to objects that cannot be tested in the traditional manner, a technique that is usually reserved for inspecting materials in use in nuclear power plants. This technique is used to determine the microstructure of the metal or characterize the surface state of the zone under analysis. It avoids the need to take any samples from valuable "heritage" objects and can be applied to a discrete area less than one centimetre square.The replicas technique has been applied to the four Mingqi funerary statuettes (some of which are 2000 years old) in the Cernuschi Museum.
Thanks to highly focused and high-energy X-rays (a.k.a hard-raytechniques), pieces of steel as thick as 40 cm can be x-rayed with images of exceptional quality. In nuclear power plants, the MINAC accelerator is used to sound cast metal parts like volutes and cool antpump casings or even parts that are difficult to reach. The design ofthe MINAC is another of its assets, enabling it to be transported to sites and implemented in complete safety.
The MINAC has been used to examine the internal structure of the four bronze statues cast by the Keller brothers at the request of Louis XIV for the façade of the château of Versailles. The inspection threw up a number of surprises : thin remains of the metallic framework, traces of former restoration, a large number of defects on the statue of Apollo. Henceforth, the Domaine de Versailles can now draw on valuable research to work out a preventive conservation plan. At the château of Fontainebleau, the Apollo of the Belvédère in bronze in the Galerie des Cerfs, cast for François Ist by Primatice, has also benefited from radiographic analysis with the MINAC.
The inspection revealed a virtually intact internal metallic structure and Roman-style assemblies for the handsand the drapes.
It allows direct exploration of the inside of a structure or a work of art. Widely used by nuclear plant operators, it helps find migrant bodies, for instance, in the condensers of nuclear plants. Endoscopy was used to examine the insides of the legs of the Keller statues at Versailles. Inserted under their base, the endoscope revealed the residual presence of the casting core. To go further, another technique was need, namely radiography.
This combined endoscopy-radiography technique had already been used to examine the engine of a German fighter conserved at the Caen Normandy Landings Memorial. the results revealed the absence of fracture and cracking of the different metals, despite the violence of the accident, and enabled researchers to work out an electrolytic treatment for conserving and restoring the engine without dismantling it.
Taking a closer look