The researchers used a battery of techniques to investigate the remains, including mass, infrared and atomic-emission spectrometry, electron microscopy, pollen analysis and, unusually, the help of the leading 'noses' of the perfume industry: Sylvaine Delacourte from Guerlain, and Jean-Michel Duriez from Jean Patou.
Odour analysis is a new technique for palaeopathology, but Charlier says that he hit on the idea after being struck by the variety of odours of other historical corpses. Delacourte and Duriez sniffed the relics and nine other samples of bone and hair from Charlier's lab without being told what the samples were. They were also not allowed to confer. Both smelled hints of 'burnt plaster' and 'vanilla' in the samples from the relics.
The plaster smell was consistent with the fact that Joan of Arc was burnt on a plaster stake, not a wooden one, to make the whole macabre spectacle last longer. But vanilla is inconsistent with cremation. "Vanillin is produced during decomposition of a body," says Charlier. "You would find it in a mummy, but not in someone who was burnt."