STEP 2: A man manipulates a machine to turn theselected bark strips into sheets.[Photo/ShanghaiDaily.com]

In order to remember his teacher, Kong wanted to make the best paper to paint a portrait of his master. One day he happened to see an ancient Qingtan tree, a common species of elm in the area, that had fallen near a river.

Due to years of erosion from the water and exposure to the sun, the tree bark had turned white with some long and clean fibers. Kong removed the bark and after some trial and error, he invented Xuan paper, which is white, smooth and has a fine texture.

This is similar to how Liu defines Xuan paper — handmade from the county’s Qingtan trees and Shatian straw, then soaked in mountain spring water. The production process includes more than 100 steps in some cases as paper-makers have invented steps that have been kept secret from others. The process includes steaming and bleaching the bark, as well as the addition of a variety of juices.

"Everything is done by hand and every material used is grown in Jingxian County, all of which makes Xuan paper stand out," says Xing Chunrong, 61, who has been making the paper for more than four decades.

"Each worker only knows one or two steps of the process because each step takes several years to master," he says.

Normally it takes about 18 months from start to end to produce a piece of Xuan paper, a national intangible cultural heritage.