- Rolled scrolls protect, but often at the cost of curling (Image: Linda Nylind/Guardian)
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Tzay-Ming Hong at the National Tsing Hua University in Taiwan and his colleagues decided to investigate curling scrolls after a trip to the National Palace Museum in Taipei, where they talked to art conservationists about ways to use physics to protect hanging scrolls. "Like the mounting masters before them, over the span of more than 2000 years, they did not think this problem was at all solvable," says Hong.
The team modelled the problem on computers and with real paper and plastic films. They found that rolling causes the back layer of a scroll to stretch along its length. This means the paper shrinks back when the scroll is laid out flat, causing it to expand along its width and curl.
Stiffer back
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The paper backing used to mount scrolls is often replaced as part of normal restoration. So Hong's team says one solution is to replace the backing on scrolls with paper that has fibres aligned with the long edges, increasing stiffness in that direction. Adding extra layers of paper to the sides has a similar effect.
Alternatively, making tiny perforations along the entire backing sheet with a stiff brush will reduce the amount of stretch that converts into curling. The team saw similar results for plastic films, which suggests that these techniques could be useful for designing flexible electronic displays, which also curl after rolling.
"No one would have guessed that studying ancient Chinese paintings would lend a lesson to modern technologies such as flexible electronic paper," says Hong.
Journal reference: Physical Review Letters,DOI: 10.1103/PhysRevLett.112.034302