Discovering manganese-based blacks in the grave goods of Kha and Merit (Egypt, 1450-1400 BCE): Multidisciplinary investigation on use and nature

As part of the “TT8 Project”, several research groups examined the grave goods from the Theban Tomb No. 8 of Kha and his wife Merit who lived during the second half of 18th dynasty and were discovered by the Italian Archaeological Mission led by Ernesto Schiaparelli. Thanks to the collaboration of Egyptologists, conservators, and scientists, numerous state-of-the-art, non-invasive methods were used to examine and characterize the objects found in the tomb. During this comprehensive investigation, for which a fully non-invasive approach was designed, the preliminary results for three polychrome wooden caskets showed the unexpected presence of manganese in the black areas in combination with the carbon black ink also present in the black decorations. In addition to MA-XRF analysis, which allowed for the discovery, an innovative imaging method was applied for faster discrimination of black pigments. This method is based on the optical spectral differences between manganese-based blacks and carbon black in the short-wave infrared – with a maximum difference in the range of 1400–1700 nm – and is comparable to a photograph in terms of acquisition time. By using an InGaAs camera with an interferential long-pass filter of 1400 nm, the images were acquired first on a series of mock-ups and then on the wooden caskets. Using false color imaging representation, the areas painted with manganese black showed a clear red false color, in contrast to the black false color of the areas painted with carbon black. The results are fundamental to understanding whether the use of manganese black could be more widespread than reported in the literature so far.