Type and Sources of Salt Efflorescence in Painted Stone Carvings from Pujiang Museum, Sichuan, China

Painted stone carvings from Pujiang Museum in Chengdu were excavated from the Ming tombs near to Chengdu Metro Line 7. The Ming burial sites were the eunuch graves of the Shu King, and their tomb was constructed mostly of stone and decorated with paintings and carvings on its surface, which are of great value. However, during their burial, these painted stone carvings suffered significant salt damage. In this research, we performed optical microscope (OM) analysis, Raman spectra (RAM), ion chromatography (IC) analysis, X-ray fluorescence spectroscopy (XRF), X-ray powder diffraction (XRD), and petrographic microscopy (PM) to clarify the salt composition and influence. According to the results, the majority of the salt on the painted layer is CaSO4 center dot 2H(2)O. Before excavation, interaction between acid rain, soil, and groundwater created salt efflorescence on the paint layer's surface. The deterioration of the paint layer caused by gypsum was divided into two stages: before excavation and during in situ preservation. This research provides a foundation for the removal and prevention of salt efflorescence.

Automated summary

The painted stone carvings from Pujiang Museum in Chengdu were discovered in the Ming tombs near Chengdu Metro Line 7. These tombs, which were the burial sites of the eunuchs serving the Shu King, were primarily made of stone and adorned with valuable paintings and carvings. However, these artworks experienced significant damage from salt during their burial. Through various scientific analyses, including optical microscopy, Raman spectroscopy, ion chromatography, X-ray fluorescence spectroscopy, X-ray powder diffraction, and petrographic microscopy, the researchers identified the salt composition and its impact. The majority of the salt on the painted layer was found to be CaSO4 center dot 2H(2)O. The deterioration of the paint layer caused by gypsum occurred in two stages: before excavation and during in situ preservation. This research serves as a foundation for the removal and prevention of salt efflorescence.