Characterization of gold leaves on Greek terracotta figurines: A PIXE-RBS study

New insights are presented on the composition, thickness, and application of the decorating gold leaves remaining on Greek terracotta figurines, kept in the Louvre Museum. Excavated from various sites around the Mediterranean basin, the objects are dated to the Hellenistic and Roman period (4th c. BC-1st c. AD). The thickness of the gold leaves was determined using 3 MeV H+ Rutherford backscattering spectroscopy, while the gold concentration was calculated using H+-particle induced X-ray emission. On artifacts exhibiting large gilded areas, mapping permitted to define zones of interest in both well-conserved and weathered areas of the leaves for the thickness calculation. The obtained thicknesses in the different zones are in agreement within the standard deviations, thus validating the use of point measurements performed for the other objects. For the whole studied corpus, the thicknesses ranged between 160 and 710 nm for a gold concentration mostly superior to 95%, strongly suggesting an ancient purification process as well as a developed goldbeating technique during these periods in the ancient Greek world. Tin leaves were also evidenced on several figurines, but their thicknesses were not estimated due to a strong oxidation.