"If I have to select something I am most proud of, it must be these incense burners," Zhang smiles, staring at a provincial-level award certificate hanging on the wall, which proclaims his contribution to the rebirth of Xuande Lu.

Xuande Lu, or Xuande incense burner, which was first made for the royal families during the reign of Xuande (1425-35) in the Ming Dynasty (1368-1644), is generally considered to be China's top-class copperware variety. The wealthy emperor Zhu Zhanji was a fanatical fan of such vessels. It is said he imported large sum of copper from Siam (today's Thailand), and he ordered the artisans to make 3,000 furnaces based on the shapes of classical Chinese porcelains.

However, few pieces circulated beyond the royal families and dignitaries. It is extremely rare to see real Xuande Lu nowadays, but its name has an allure for antique collectors and it's almost a synonym for Chinese copper incense burner. People during the Qing Dynasty (1644-1911) and the following period (1912-49) swarmed to make counterfeits.

Zhang says some of the most delicate replicas, applying a more-than-2,000-year-old method known as "lost-wax casting", also have very high artistic value. However, the details of the method, which were first used to make bronzeware, were little recorded in books and the artisans were tight-lipped with the industry secret. Continuous wars in the early 20th century and the anti-antique trend during the "cultural revolution" (1966-76) almost caused the technique to die out in China.

Zhang ran an advertising company in 1992 and made some fortune. He learned oil painting in his childhood. Although he kept drawing in the following decades, he never considered arts to be his profession until what he describes as "destiny".

Zhang became a Buddhist in 1998. Out of curiosity, he learned craftsmanship from a senior fellow Buddhist, who is a coppersmith.

"We have a saying: One incense burner represents a god," says Zhang, who greatly attributes his motive for making the incense burners to his piety. "When I'm too involved in a restless business circle, I feel inner peace sitting in front of an incense burner to worship its unsophisticated beauty.

"So, why couldn't we make our own?"

However, the antique market was then filled with low-quality replicas.

"Some people even used aluminum alloy as the material and cobbled the burners via identical metal moulds," Zhang says. "Can you expect to create artworks on the modern assembly line?"

Zhang believed it was essential to revive the "lost-wax" technique. His senior fellows had only heard the name of the method but never tried it. So Zhang had to rummage the fragmentary historical record for reference.

"I visited numerous old coppersmiths, checked a picture album published in Taiwan introducing Xuande Lu and kept experimenting."

Zhang says he threw more than 1 million yuan ($160,000) making trials for one year after he began the work in 2004, but didn't succeed in making a piece with acceptable quality.

"I dared not open the furnace to see the final work because I had enough failures," Zhang recalls his toughest time. "I almost lost all my savings but I had to continue. If I stopped without any success, I might go completely bankrupt."

Zhang's revenue in the advertising company was unable to support this gamble, and he had to simultaneously manage a hennery, reviving an old local breed known as Langshan Chicken, to make ends meet.

He finally found the traditional technique: He uses wax to carve the original moulds, and cover them with quartz powder mixed with liquid glass seven times. After drying, the works are boiled in hot water of 80 to 90 C to melt the wax and form the quartz outer skins as the moulds for casting, where the temperature can be as high as 1,300 C.

A mould can be used to make only one incense burner, and the whole process for making the piece can last for one month.

"If one step is wrong, the whole process must be repeated. Even some bubbles during heating will make a work a failure."

He adds that the heating and thickness of the quartz layer is the key because the mould could easily be broken during casting.

Polishing is also a crucial process.

"The exterior should be as smooth as baby's skin," he says. Still, Zhang regrets that his incense burners are not perfect.

"The emperor didn't care about the cost. His artisans used gold and silver to mix with copper. That luxury cannot be repeated today."

Zhang's foundation material is 90 percent copper, 5 percent tin; the remaining 5 percent is a formula, which he keeps secret. He has created nearly 200 styles and his work was listed as one of provincial intangible cultural heritages in 2011.

He is overjoyed that his work helps to sustain enthusiasm for other local cultural relics.

Bian Xueliang, 58, a former worker at a furniture factory, learned woodcarving at the age of 19. He feels sad that younger generation is not interested in the traditional artifacts.

"Most carvers swarm to more profitable industries like interior decoration," Bian says. "I also hesitated whether to stay in the industry."

He met Zhang in 2008 and found wax-mould carving to be a new place he could use his skills.

"Wax carving is highly demanding for its details. Thanks to my years of practice, it only took a short time to adapt."

Zhang's workshop hired about 10 employees and makes about 800 incense burners a year. The pieces are usually priced from 10,000 to 20,000 yuan.

Yang Hongwei, a Nantong-based artwork collector, is Zhang's frequent customer.

"It is rare nationwide to see such high-level heritage production techniques of Xuande Lu, which is even more important than the work itself," Yang says. "It is a unique contribution in terms of historical responsibility."

Nevertheless, Zhang hesitates to put much energy in marketing.

"As the Chinese traditional culture revives in recent years, the market for incense burners is huge," Zhang explains. "However, if I expand my output, many people will copy my work in a rough way, and the works' value will largely decrease, which will harm me and our culture."

He felt lucky when Nantong municipal government established a 4,300-square meter park — Intangible Cultural Heritages Workshop — in February for 18 heritage craftsmen to exhibit their works for free.

"This is not only a market," says Cao Jinyang, chief of the municipal office in charge of the intangible cultural heritages protection. "It is a platform for the items to show their vitality and connect more with the general public to promote the traditions.

"Without such production of such relics," Cao says, "they will easily die in modern times".

Contact the writer at [email protected].

Ding Congrong contributed to this story.