Abstract
Qi-Wa is the phenomenon that occurs in handscrolls and hanging scrolls; once we spread the roll paper, it is easy to notice the up curl on the sides of paper. In addition to aesthetic aspect, it results in irreversible effects such as tears and pigment loss, which has troubled Chinese artisans for more than 1600 years. Previous works suggest that Qi-Wa comes from the climate effect, conservation conditions, and/or mounting procedures. However, we find that the main cause of Qi-Wa is the spontaneous extrinsic curvature incurred from the storage. According to experiments, we find that the height of Qi-Wa obeys simple power laws with the scroll's length, width, thickness and curvature. This result is supported by Molecular Dynamics (MD) simulation and theoretic derivations. Based on the theory, we propose several methods to reduce Qi-Wa. These methods have been tested by use of real mounted paper and simulations, and are proved workable. Our study can be applied to modern technologies, since similar warps occurs not only in Chinese scrolls but also in industry productions of flexible display, electronic paper, and paper solar cell circuit.