Method uncovers color hidden in ancient Greek marble

One of the archaeological delights found in the ancient Greek city of Delphi is a frieze that depicts scenes from the Trojan War, including a sculpture of the hero Achilles wielding a shield decorated with the head of the monster Medusa. Nowadays, the monster’s hair—like the rest of the frieze—is the mottled brown color of ancient marble, but it wasn’t always so. Medusa’s tresses were once painted green, according to a team of researchers led by Matthias Alfeld and Philippe Walter of the University of Pierre & Marie Curie, in Paris (Anal. Chem. 2016, DOI: 10.1021/acs.analchem.6b03179). To detect the long-lost pigments in Medusa’s hair, the team developed a new X-ray fluorescence (XRF) technique that can map the surface of 3-D objects. The method combines 2-D XRF with data from a photograph-based technique called photogrammetry and computer modeling. By using the new technique, the team found traces of copper all over Medusa’s hair, suggesting her tresses could have been painted with a green or blue copper pigment. The researchers also detected tiny green crystals in the hollows between Medusa’s tresses using a microscope, leading them to conclude that the monster’s hair was once green.