A repaired fresco. [Photo by Wang Kaihao/China Daily]

After checking previous restoration samples from the academy, Ngakwang Chozen nodded his head, and held a blessing ceremony for the project, which takes care of 966 square-meters frescoes. He also daily visits the site to make sure the repaired ones are identical with original facades.

"When repairing frescoes, we stick to principles of minimum prevention," Guo said. "If some parts of images are already too faded, we usually only use methods to prevent them from deteriorating further and will not redraw."

However, he added that there are some unique cases.

"For example, when repairing a deity image, we cannot leave it incomplete considering pilgrims' emotions," Guo said.