Abstract: Most of the harm to the paintings and calligraphy is related to "the force". However, few studies have been reported on the research of the mechanical behavior. Xuan paper is a primary material of the mounting of Chinese paintings and calligraphy. Dimensional variation occurs upon changes in its moisture content during the drying process, and serious deformation may affect the stability of the paintings and the effects of the mounting. Digital image correlation was used to measure the wet deformation of single-layer Xuan paper and the sample of a mounted painting on two layers of Xuan paper, with considerations of dimensional changes caused by wetting and the influences on the deformation from Xuan paper's fiber orientation upon drying on the wall. The results show that the mechanical properties and wet deformation were related to the fiber orientation of Xuan paper, and that fiber orientation was the main contributing factor in the influence on deformation in drying. In addition, excessive shrinkage in both vertical and horizontal directions was observed in new Xuan paper due to the existence of internal stress. Suggestions are thus provided on improvement, which will help raise the quality of mounting and restoration of cultural relics such as calligraphy and paintings.

Key words: Xuan paper, wet deformation, mounting techniques, digital image correlation