New insights into a polychrome Middle Kingdom palette applied to a wooden coffin: A multidisciplinary analytical approach

Abstract

A wide range of non-invasive and micro invasive analytical techniques has been used to uncover new and unexpected information on a polychrome wooden coffin from the Middle Kingdom of ancient Egypt.The results of a comprehensive diagnostic investigation carried out on the pictorial layers, by means of multiple non-invasive and micro invasive analytical techniques: multispectral imaging, optical microscopy (OM), X-ray fluorescence (XRF) spectroscopy, visible reflectance spectroscopy (Vis-RS), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) provided new insights concerning its original manufacture and techniques, which, most surprisingly, revealed that the green painted layer is originally made of green earth as glauconite, which is detected for the first time in the chromatic palette of the Middle Kingdom in ancient Egypt. An equally interesting aspect of the coffin's manufacture is the presence of a blue- grey layer, which surprisingly showed the use of a mixture of anhydrite, gypsum calcite, and charcoal particles as an unusual technique, which is similar to the technique called "optical blue" in the ancient world. Furthermore, the results showed the use of a mixture of yellow ochre and orpiment to decorate the studied coffin as the first evidence of the chromatic palette of the Middle Kingdom. The results also indicate the continuous use of artificial and natural earth pigments in accordance with previous analyses of ancient Egyptian coffins such as Egyptian blue pigment for the blue painted layer, anhydrite, gypsum, and calcite for the white painted layer, hematite for the red painted layer, and carbon (charcoal) for the black painted layer. Moreover, reflected images, recorded by polarised microscopy, provided a representation of the wood species used to construct the coffin. It is confirmed that the wood used to construct the boards of the coffin was Ficus sycomorus, which is native to Egypt, while Tamarix sp. was used for dowels as was common in ancient Egypt.