Can earthen plasters be effectively applied on different substrates?

Abstract

Abstract Earthen plasters have been widely used in historical buildings, especially in wall paintings in northwest China. However, the properties of earthen plasters have deteriorated dramatically under long-term weathering. In order to investigate one of the key issues in plaster restoration, i.e., whether the plaster can be effectively applied on different substrates, seven compositions of plasters were prepared and applied to three types of substrates modeled after actual wall painting supports. Shrinkage of the plasters was measured and the adhesion of the plasters to the substrates was characterized by a shear test using a designed device. The results show that the shrinkage of the plaster depends on the material composition of the plaster and is almost independent of the type of substrate. The addition of vegetal fibers to earthen plaster can effectively improve interfacial adhesion. The type and the surface roughness of the substrate have a significant effect on the adhesion between the earthen plaster and the substrate.