The regular glue used in ancient sculpture restoration in northern China was not practical in hot, humid Chongqing. Zhan's team had to find local artisans who are familiar with lacquer to make paint in old ways.

"You can use new techniques on many occasions," Zhan smiles. "But you have no other choice than copying ancient ancestors in some cases."

Though Zhan says it is not easy to precisely predict how long the statue will last without major restoration in the future, he confidently predicts it will remain intact for at least 50 years.

Meanwhile, the overall project is far from the finish line. The pavilion housing the statue, built in the Ming Dynasty (1368-1644), will be restored soon. The team will also install an air-circulation system in the pavilion to minimize the toll of air and water.

"The macro environment of this statue and the whole Dazu Rock Carvings has not changed that much," says Tong Mingkang, deputy director of the State Administration of Cultural Heritage, who remains cautiously optimistic. "Therefore, supervision of this World Heritage site still needs to be enhanced to control further damage."

"When we judge the value of the Dazu Rock Carvings," says He Hong, a professor from China Academy of Art, "we have to put it into the holistic cultural context of the Southern Song Dynasty.

"But we cannot say whether it is successful. We'd better let future generations judge."

Tan Yingzi contributed to this story.