Investigation of gilding materials and techniques in wall paintings of Kizil Grottoes.

• Tin and gold foils are used in gildings of Cave 171 in Kizil Grottoes. • Lac resin was identified for the first time as mordant for adhering gold foils. • Drying oil was applied as mordant in the tin gilding. The present work reports the new characterization results of the gilding materials used in Cave 171 of Kizil Grottoes, China, which is dated between 5th and 7th Century, A.D. Tiny samples collected from four different gilding decorations were analyzed by scanning electron microscopy with element energy dispersive X-ray spectroscopy (SEM-EDS) to identify the gilding structure and inorganic materials. It was discovered that both tin and gold leaves were used as the gilding foils. Interestingly, different organic mordants were used under different foils. The pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) results show that drying oil was applied as the mordant for the adhesion of tin foils while lac resin was used for gold foils. The presence of lac resin has been further confirmed by liquid chromatography-electron spray ionization-mass spectrometry (LC-ESI-MS). Although lac dye has been detected as the red colorant in wall paintings of Buddhist grottoes, its use as gilding mordant is a new finding. These gilding materials found in the wall paintings of Kizil Grottoes may provide some evidence of painting materials and techniques exchange along the Silk Road. [ABSTRACT FROM AUTHOR]