广元千佛崖石窟石刻彩妆颜料的分析

四川省广元千佛崖石窟是四川境内最大的石窟寺和摩崖造像群，承载着古代社会的历史信息，对研究当时的政治、文化和社会生活意义重大。千佛崖石窟在自然环境因素的长期作用下，目前受到多种严重病害的侵蚀，亟待保护。为了获取石刻彩妆的成分与工艺信息以支撑彩妆的保护工作，应用X射线衍射分析、剖面显微分析、扫描电镜能谱分析、激光拉曼光谱分析等方法，对广元千佛崖8处洞窟的已脱落彩妆颜料层样品进行了分析。X射线衍射分析鉴定出了铁红(Fe₂O₃)、朱砂 (HgS)、铅丹(Pb₃O₄)、炭黑等颜料成分，以及铅白 (PbSO₄)、石膏(CaSO₄·2H₂O)、长石、二氧化硅等打底层和岩体的组分，验证了样品脱落的原因是岩体的劣化。剖面显微分析和扫描电镜能谱分析表明，不同洞窟的彩妆制作工艺有区别，有的颜料直接施加在岩体表面，有的则在颜料层和岩体间有一层主要为硫酸铅的打底层；样品表面蓝绿色颜料的含量很少，仅通过激光共聚焦显微拉曼光谱成功地识别出来，其鉴定结果为蓝铜矾Cu₄SO₄(OH)₆·2H₂O]。蓝铜矾作为颜料使用的报道很少。由于其矿物含量较少但分布广泛，古代一般不将其分离出来单独使用，而人工合成的碱式硫酸铜类颜料布勒门绿（Bremen green）出现于18世纪-19世纪，如果有纯碱式硫酸铜单独使用的情况出现，就意味着有近现代重绘的可能性，将有助于彩绘类文物保存历史的判断。该研究不仅为千佛崖石刻彩妆的保护提供了依据，丰富了文化遗产中使用蓝铜矾颜料的案例，更对彩妆的保存历史研究有潜在价值。

Technological Analysis of Pigment Layers in the Guangyuan Thousand-Buddha Grottoes

Guangyuan Thousand-Buddha Grottoes arethe largest group of cliff figures and temple grottoes in Sichuan Province.The grottoes are of great value,studying of which contributes to a better understanding of ancient politics,economics and culture.However,after a long period of weathering,they are suffering from various kinds of diseases and in urgent need of protection.We conducted phase and component analysis to elucidate the pigments and technologies of painting layers and provide evidence for conservation,with polychrome fragments that fallen from eight different grottoes as samples.The X-ray diffraction(XRD)analysis identified pigments such as iron oxide red(Fe₂O₃),cinnabar(HgS),minium(Pb₃O₄)and carbon black,as well as lead white(PbSO₄),gypsum(CaSO₄·2H₂O),feldspar and quartz in preparation layer and support rocks.This result confirmed that deterioration of the rocks is the main reason of the pigment layer fallen.In analyses of microscopic examination on cross-sections and scanning electron microscopy with an attached energy-dispersive spectrometer(SEM-EDX),two different painting technics,i.e.preparation layer of lead white and painting without preparation layers were recognized.Because of its low concentration,the green-blue pigment could only be recognized using laser confocal Raman Microspectroscopy,and the result was langite(Cu₄SO₄(OH)₆·2 H₂O).Langite is seldomly reported as a pigment.As an uncommon but widespread mineral,it is not likely to be separated from other copper minerals in ancient pigments.Manufactured basic copper sulphate pigment(Bremen green)is synthesized in the eighteenth and nineteenth century.As a result,the painting may have been redrawn in modern times if pure basic copper sulphate pigment is discovered.These results have provided scientific evidence for related conservation research and provided a new case of using langite as pigment.In addition,langite may also be helpful in studying the preservation history of grottoes.