麦积山石窟131窟壁画材质及制作工艺研究

Study on the production technology and materials for murals in Cave 131 of Maijishan Grottoes

麦积山石窟保存的大量壁画是研究石窟壁画艺术与佛教文化的珍贵实物资料。利用悬浮沉淀法、纤维形貌观察法,结合X射线荧光、X射线衍射、激光粒度分析、拉曼光谱等检测方法对麦积山131窟壁画残块地仗层及其添加物、颜料层进行科学检测分析。分析结果表明:131窟壁画地仗层使用的黏土应该是麦积山周边稍远地区的天然细质黄土,且粗、细泥层中均人为添加有砂粒,但粗泥层中添加砂粒较细泥层更多、颗粒较大且颗粒度不均匀。粗泥层中添加纤维为麦衣、麦秆,细泥层添加麻纤维。壁画烟熏污染物主要显色物质为燃料燃烧产生的炭黑,红色颜料主要是铅丹、朱砂、铁红,白色底色层的成分是方解石。研究结果不仅为探讨麦积山石窟壁画材质与制作工艺提供了基础数据,而且对后期壁画的保护修复也具有一定的指导意义。

Maijishan Grottoes were first built in the Later Qin Dynasty of the Sixteen Kingdoms Period and have been excavated and repaired for more than 1600 years,showing distinctive features of the times.During the Northern Wei Dynasty,Maijishan Grottoes gradually formed a style integrating the cultures of Buddhism and Central Plains.At present,relevant research is mainly focused on the artistic style of grotto statues and murals.Cave 131 was excavated in the late Northern Wei Dynasty and has been covered with a layer of smoke pollutants.The contents of its murals are still unknown,but the murals have a large hollow area and have started to fall off.The raw materials and production technology for murals are indispensable data and basis for their scientific research,protection and restoration.However,according to the existing literature,scientific research on the materials for murals of Maijishan Grottoes is scarce,and that on their production technology is basically blank.In this study,we conducted a scientific analysis of the ground support layer,and its additives and pigments,of Cave 131 mural fragments using the suspension sedimentation method and fiber morphological observation,in combination with laser particle size analysis,XRD,XRF and Raman spectrometry,etc.The results indicate that 1)the smoke pollutants on the mural surface were thick,tightly adhering to the pigment layer and penetrating into its interior,and there was a serious cracking problem;2)the internal hollowing out between the pigment layer,base layer and ground layer of the murals is a serious hidden danger;3)clay used for the ground layer was a natural fine loess collected from a relatively more distant area around Maiji Mountain;4)in the fine mud layer,washed fine sand and hemp fibers were manually added,while in the coarse mud layer,more and larger uneven sand and unwashed wheat straw were added,which could effectively reduce the shrinkage and cracking of the ground layer.The main expansion of this study includes the following three aspects:1)the smoke pollutants tightly adhering to the mural surface were one of the factors that caused the peeling of mural layers,and the coverage of smoke pollutants could delay the corrosion and blackening of lead,providing a reference for later research on corrosion and protection;2)through the analysis,it was found that the particle size distribution of loess soil samples collected was obviously different,while the particle size distributions of the mural samples and Dianzi Village loess soil samples were consistent,so it was speculated that high-quality clay areas from far away were collected as the raw material for the ground support layer of murals in Maijishan Grottoes;3)the particle size distribution of natural loess sand was highly consistent,far less than the particle size distribution of soil samples from the ground support layer,which could determine the gravel addition and processing methods in the ground support layer,and to some extent,it has solved the problems of soil sample sources and processing measures for the ground support layer of murals in Maijishan Grottoes.This study provides a reference for exploring the materials and production technology for murals in Maijishan Grottoes,and also provides a scientific basis for the subsequent analysis of mural diseases,protection and restoration.