Many caves he visited house precious murals dating to more than 1,000 years ago.

Changes in humidity and temperature in the caves, caused by visitors, can greatly damage the murals as they were painted mainly by mineral pigments.

In some popular grottoes open to the public, such as those in Gansu's Dunhuang that are home to one of the finest Buddhist arts in China, visitors' stay in a single cave is limited to less than 15 minutes for protection purposes.

"I feel really lucky to have the chance to study these murals at such close distance," Han says.

However, the chance also means many difficulties. Sometimes he has to work inside a cave for five to seven hours. Han either stands on his knees or squats to paint for hours because some caves are small.

Usually, a grotto is carved into the cliff face－either in a desert or on a mountain.

Han has to walk or climb a long way to reach his destination with a clay board weighing up to 25 kilograms.

"I don't think it's hard for me. I love mural art and enjoy what I do," says Han who graduated from the Xi'an Academy of Fine Arts in 2016.

Before copying murals, he was an ink artist and took part in some mural restoration projects in Xi'an, Shaanxi province.

In 2017, he joined a project organized by the Gongbi Academy of the Chinese National Academy of Arts in Beijing.

The project trains people from museums, art schools and art institutions in copying murals and builds a solid team for relic restoration.

Supported by the China National Arts Fund, the project was launched in 2017 and attracted more than 800 applicants. It finally selected a team of 40, mostly in their 20s and 30s.