Understanding qi-wa, the curling of scrolled artwork

In the Chinese and other traditions, paintings are executed on long paper or silk scrolls. On display, those artworks may be plagued by qi-wa, a curling up of the side edges that can tear fibers and dislodge pigment. Many analyses to date of qi-wa have focused on such factors as environmental humidity or the glue used to affix a painting to its mounting. But a group of Taiwanese physicists and conservationists led by Tzay-Ming Hong of National Tsing Hua University have shown that qi-wa can be explained by a physical mechanism put into play when the art is rolled up for storage. Rolling compresses the inner, painted face of the scroll in the long direction and stretches the outer face. When the scroll is removed from storage, the strain relaxes. As a result of the Poisson effect, the art face gets compressed in the transverse direction, the back face...