Beijing, often tagged as China's cultural center, has its fair share of traditional art forms on offer. Few though are as close to extinction as Liaoqi with only four practitioners in China, all from the same family and living in Beijing, believed to still master the mysterious material.

"The tiles on the roof of the Forbidden City and the Nine Dragon Screen in Beihai Park are made of Liaoqi," said Liu Yu, one of the four.

Liu, his brother and their parents, are the last remaining experts on the almost-forgotten skill. Their work used heat to turn a core material - the majority of which is glass, plus 24 percent lead dioxide and some heavy metal colorings - into small items of beauty.

In ancient China, the correct term to describe both the material and the art form was "Liuli".

"The name was changed to 'Liaoqi' by Emperor Qianlong," Liu said, referring to the emperor's period of rule (1736-1796) during the Qing Dynasty (1644-1911).

Liu said Qianlong had not been a strong supporter of the use of "Liuli", since its Chinese characters sound like the word for "homeless".

All that changed again in 1987 when a Taiwan company started mass-producing the material as ornaments and trinkets, but with an altered composition that increased the proportion of glass to boost attractiveness. They called it "Chinese Liuli".

Despite selling well, Liu disagrees with the new formula, claiming it has little in common with the original craftwork.

He said genuine Liaoqi is shaped while in a semi-solid state over a flame. Practitioners then manipulate the material, often using their hands.

"It is like sculpting," he said. "But more difficult because it is done over the fire."

Liu said the Taiwan product is made using production-line molds, in 1,400 C temperatures that are hot enough to alter the shape of glass. The end result is a mostly-transparent and extremely colorful look, while Liu's works are translucent or even opaque.

Liu said he can make four to five pieces every day, though each piece is usually finished in just 20 minutes.

"Working so close to a fire is no easy thing," he said.

He said he understands that his pieces lack a modern feel, but he refuses to let go of tradition.

"Art is not judged by color," he said. "And traditional art should never yield to the market."

Using a gas burner and a pair of long tweezers, Liu holds a stick of raw Liaoqi in his left hand and sets it ablaze. After pulling, pressing, clamping and twisting, a lifelike peony blooms in his hands.

Though it looks easy, Liu, 40, said he has been honing his technique since age 5. Burns on his left hand are the telltale mark of a Liaoqi artist.

"If you don't get burned in a day's work, you did not work at all," he said.

The peony is Liu's area of expertise. His brother is skilled at calabashes, pumpkins and vases and their father deals with making birds and Chinese cabbage.

The biggest star of the family, according to Liu, is their mother, Xing Lanxiang. She is the only person recognized by the central government as the master of Liaoqi.

"She learned her skills from four masters during the 'cultural revolution'," said Liu. "There is no area she is weak in."

Liu pointed at a pair of ornaments, an elephant and jaguar, adding that, "they were made by her when former premier Zhou Enlai was still alive."

He said Xing made the sculptures at the Beijing Liaoqi Factory, using a special flame large enough to deal with such a heavy quantity of the raw material. The factory has since closed and the skill of making grand pieces lost.

The Liaoqi factory once employed more than 600 professionals in the 1980s. After it closed in the early 1990s, every worker shifted their profession to make ends meet - only Xing persevered.

"This art form might die with the last successor, if support and protection from the government doesn't arrive."