The delicate craft, mainly used in the past to decorate imperial ornaments like crowns and hats, has developed into a precious modern-day folk art.

"Now, we mostly do jeweled brooches, hairpins and corsages, depending on demand," Li said.

In 2006, he returned to Chongqing with plans to tutor a qualified inheritor. "I have to do my best, even though I am old," he said.

Li usually goes to bed at 2 am and gets up at 7 am. He visits his apprentices at their studios to offer technical guidance and supervision, and paints in his spare time.

So far, he has tutored more than a dozen apprentices. Three now run filigree inlay sales shops and six run studios making jewelry and offering training courses. The combined annual revenue from the studios now stands at around 6.4 million yuan ($1 million).

Shi, who became Li's apprentice six years ago, opened a studio in Chongqing in April.

"As the country attaches more importance to intangible cultural heritage, there might be an opportunity," she said.

Another apprentice, 32-year-old Zuo Shuqiao, makes about 6 million yuan a year and employs over 60 workers.

Around 1,700 students have been trained at the six studios since 2014, helping revive the art form all over the country.