ABSTRACT

The plaster of the wall paintings at Mogao Grottoes is all made of earth, and the migration of water and salt in this kind of plaster is one of the most important factors that cause the deterioration of the wall paintings. However, the characteristics of the migration in the earthen plaster, which are quite crucial for the research on the formation mechanism of deteriorations and the conservation treatments, have not been fully comprehended yet. In order to study the migration rule of water and salt in the plaster, different types of simulated plasters were made according to the material composition of the plaster at Mogao Grottoes. Through a series of experiments and analyses, pore-size distribution, microstructure and capillary migration rules of the plasters were characterized. Due to the difference in capillary performance, a capillary barrier effect will occur at the interface between the coarse plaster and the fine plaster. After the capillary migration, the salt is more likely to accumulate on the area of the capillary front, which will directly damage the paint layer. And the salt-water migration process inside the plaster will make the plaster structure loose and porous. Therefore, it is important to prevent rain infiltration and the rising damp after rainfall for wall painting conservation.

摘要

莫高窟壁画的灰泥全部由泥土制成，这种灰泥中水分和盐分的迁移是造成壁画劣化的最重要因素之一。然而，对于研究劣化形成机制和保护处理至关重要的土灰迁移特性尚未得到充分认识。为研究石膏中水盐的迁移规律，根据莫高窟石膏的材料组成，制作了不同类型的模拟石膏。通过一系列的实验和分析，表征了石膏的孔径分布、微观结构和毛细迁移规律。由于毛细管性能的不同，粗灰泥和细灰泥之间的界面会产生毛细屏障作用。毛细管迁移后，盐分更容易聚集在毛细管前沿区域，直接破坏漆层。而石膏内部的盐水迁移过程会使石膏结构疏松多孔。因此，防止雨水渗入和雨后湿气对壁画保护具有重要意义。