Unlike other sets of ancient books, which used a uniformed format and the same materials, Tianlu Linlang was miscellaneous due to the wide time span of the source material. In this collection, the pages varied in their composition greatly, and some were even made of silk.

"That situation throws up a huge challenge," Zhu says. "We have to draft a tailored plan for each copy."

Restorers only use glue that is handmade by themselves, for fear that the chemicals in factory made adhesives would further damage the pages. To dye the patched paper to match the yellowing color of the original pages, various kinds of natural materials, including precious Pu'er black tea, were used.

"However, for such a cultural treasure, all the diligent work was worthwhile," Zhu says.

Viewing the exhibited books selected from Tianlu Linlang, Zhu feels relieved.

"When handling the broken pages, it's like we're preparing a funeral for them," he says. "But the consistent work of the restorers has brought about a second life for the books."