大足石刻舒成岩摩崖造像表面贴金工艺研究

Research on the Gold Foil Overlaying Technology on Shuchengyan Cliffside Sculptures of Dazu Rock Carvings

舒成岩摩崖造像是大足石刻重要的组成部分,对研究宋代道教神灵体系和中国道教发展演变历程具有重要的历史价值。利用激光共聚焦扫描显微镜(CLSM)、扫描电子显微镜(SEM)、X射线荧光光谱仪(XRF)、傅里叶红外光谱仪(FTIR)和X射线光电子能谱仪(XPS)对舒成岩摩崖造像第3龛主尊紫微大帝面部和手部的贴金层进行检测分析,发现舒成岩摩崖造像妆金主要采用了贴金工艺,采用高纯度的金箔,并以金胶油作为粘结剂。其中,金胶油采用桐油作为成膜剂,添加了密陀僧(PbO)作为催干剂,同时也添加了朱砂(HgS)增强金箔色泽及粘结度。随着金胶油层风化酥粉,贴金层中金箔发生开裂和严重脱落的现象,需要进行加固保护处理。研究结果为认识舒城岩造像表面的妆金技术提供了重要参考数据,也为科学认知我国古代贴金技术及其保护修复提供了重要参考资料。

As an important part of Dazu Rock Carvings,Shuchengyan Cliffside Sculptures are of great significance for the study of Song Dynasty Taoist divine system and the development of Chinese Taoism.The paper analyzes the gold-overlaid on the surfaces of face and hands of Emperor Zi Wei's Statue in cave 3,which was constructed during Shaoxing peiord of the Southern Song Dynasty(1131-1163 AD).Multiple analytical technologies were applied,such as confocal laser scanning microscope(CLSM),scanning electron microscope(SEM),X-ray Fluorescence Spectrometer(XRF),Fourier Transform Infrared Spectrometer(FTIR)and X-ray Photoelectron Spectroscopy(XPS),to study the composition,structure and properties of the gold foil.The results indicate that the gold foil has a high gold content over 80%,while its CLSM images show that it's adhered to a thin red layer,and many notable diseases such as cracking,peeling and curling have emerged.With the help of FTIR,the red layer is identified as a tung-oil-based gilding size with the peaks at 2926 cm-1 and 2856 cm-1 due toυs(C-H)andυas(C-H)of alpha-eleostearic acids,a peak at 1746 cm-1 due toυs(C=O)of fatty acids in oil,a peak at 1636 cm-1 due toυs(C-O)of carboxylate in oil,and a peak at 1456 cm-1 due toδ(C-H)of methyl in oil,which shows in red by adding cinnabar(HgS)in liquid tung oil to brighten the color of gold foil.Meanwhile,litharge(PbO)is detected by XPS with the fitted Pb 4f7/2 peak at 138.9 eV and the Pb 4f5/2 centered at 143.7 eV,which acts as desiccation.Gold gluing oil was wildly used to bond gold foil with the matrix in ancient China.In this case,the cracking and peeling diseases of gold foil are observed by CLSM,which result from weathering of the gold gluing oil.The outcomes of the research benefit for the study of gold foil overlaying technology in ancient China and cultural relic conservation.