Investigation on gilding materials and techniques of murals in Cave 55 at Mogao Grottoes

Cave 55 of Mogao Grottoes, which was excavated in the early Northern Song Dynasty and renovated during Western Xia, has murals richly adorned with gold foil. A systematic analysis was carried out on the gilding materials and techniques in Cave 55, including optical microscope observation (OM), scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), X-ray diffractometer (XRD), confocal Raman microscopy (CRM), Fourier transform infrared spectroscopy (FTIR), pyrolysis with gas chromatography and mass spectrometry (Py-GC/MS). Analysis revealed significant differences in the materials used for gilding application between the murals of the Northern Song Dynasty and those of the Western Xia and the gold foil used in the Mogao Grottoes during the Cao Family Guiyi Circuit period likely originated from tribute and rewards given by the Central Plains Dynasty. The findings can serve as a reference for gilding research of other caves at Mogao Grottoes and grottoes along the Silk Road.