ONCE exclusive to imperial courts and government officials, Guan kiln chinaware is highly appreciated - but very difficult to produce. Xu Wenwen discovers more about one man's efforts to revive the ancient porcelain-making techniques and formulas.

China has a long tradition of porcelain making, and one of the high points was during the Song Dynasty (960-1279) when the Guan kilns were operating.

Guan kilns refer to official kilns directly run by the government, the products of which were exclusively supplied to the imperial courts or government officials, and accordingly became one of the most appreciated among all kinds of chinaware.

The characteristic of Guan work is its eggshell porcelain coupled with a thick glaze that gives it a lustrous, bright finish of fine greenish white jade.

Many Guan works have cracks that create distinct crisscross patterns as a result of how the porcelain and glaze expand differently when heated. The porcelain has fairly high iron content that expands a little bit more than the glaze, resulting in large or small surface cracks, although the surface remains smooth.

Guan kiln porcelain can also be identified by its distinctive "purple mouths and iron feet."

The "purple mouth" is due to the glaze being fired at high temperatures, causing it to melt and stream down the vessels, leaving the glaze on the rims thinner and with a purplish tinge. The "iron feet" are unglazed, leaving the dark iron-rich clay fully exposed.

Today, modern duplicates are made by much developed technology, but only a few of them are as superior as the old ones due to insufficient expertise and the inferior quality of clay.

Despite such challenges, some artists are struggling to revive the technology and bring Guan kiln works back to the masses.

At the Xiuneisi Guan Kiln Academy in Hangzhou, hundreds of chinaware items coated with jade-like glaze are showcased. Some modern Guan works resemble the old pieces, some are household utensils and some are creative and distinctive.

Behind them are the unsuccessful efforts to reproduce quality Guan works - the tens of thousands of pieces which were deformed, cracked and smashed in the kiln.

Ceramic master Jin Yirong is the owner of the academy and those pieces.

The non-profit academy is run with the local government's support both on finance and policy, and does not earn Jin a great income.

But 49-year-old Jin has been operating the academy for 10 years, not only to recover the Guan kiln crafts but also to further the development of today's Guan kiln artworks.

He shares his findings, such as formulas for paste and glaze, with peers once he discovers them because he believes "only by doing something well can it result in fortune in the future."

Jin, who used to be a master in Longquan, Zhejiang Province, a city famous locally for its porcelain, was introduced specially by the municipal government to revive the crafts of Guan porcelain.

His great-grandfather made duplicate Guan porcelain items and ran a china shop in Hangzhou in the late 19th century, and his grandfather later brought the technology to Longquan.

Last year, Jin was inscribed on the list of Zhejiang Intangible Cultural Heritage as a descendant of technology of Guan kiln chinaware.

Hangzhou is a vital place in Guan kiln history as it was the capital of the Southern Song Dynasty (1127-1279), and its two government potteries, Xiuneisi and Jiaotan, known for the Guan kilns of the Southern Song Dynasty, were founded respectively in 1930 and 1996.

Jin borrowed Xiuneisi's name for his academy.

One of the academy's main jobs is to recover the ancient formulas by testing the old pieces using scientific instruments.

Modern scientific ways can determine the elements contained in clay in a very short time. However, the chances of making a refined piece remains around 10 percent, similar to ancient times.

"Past dynasties used up the good clays, so we have to look for others in and around the city," he says.

"But it's just a minor reason. The quality of clay and water, the weather, and the duration and degree of heating create so many uncertainties that you never know what the end product will look like until it comes out of the kiln."

"Even when using exactly the same formula, sometimes the crisscrosses look mechanical, while sometimes they look artistic. It just totally depends," says the master.

The academy is also reviving old Guan kiln skills, and Jin recently spent three years gaining "holder nail" skills, a special technique for making "full glaze" Guan kiln porcelain.

The holder nails, also made from clay, are placed on a rack to support the chinaware at the bottom during heating, so the glaze can be applied all around the body, the bottom and the feet with only a few spur marks left on the base.

The difficulty of the skill is to make sure the slim nails don't crack or soften under the 1,300 degree Celsius heat. That's why only clay can be used to make the nails - metals liquefy at such a high temperature.

The formula for the nails is known among other ceramic workshops and masters, but Jin is the only one willing to share his studies.

"To progress along with other artists is real progress," says Jin. "This is significant in today's Guan kiln porcelain industry where talent is lacking."

In Jin's eyes, it is not because of the technology or the lack of clay that prevents today's Guan kiln works from surpassing the old ones, "the point is too few experts work in the industry," he says.

"Young grads who study pottery art in college are reluctant to limit their career to Guan kiln pottery," Jin says. "Making pottery involves suffering, the skin on our hands always cracks in winter because of the glaze's alkali, plus young people prefer to make trendy stuff.

"The old culture needs fresh blood. Indulging in imitation is meaningless. The culture needs creation based on its 'roots.'

"So the industry needs talent that is willing to persist in this art, who can be creative only after they have reached the 'roots'," he concludes.

The requirements are demanding but Jin perseveres. He is contacting the pottery department of the China Academy of Art in Hangzhou to cultivate its students and will establish a private Guan kiln museum in the near future.

Meanwhile, he is dedicated to creating fashionable Guan kiln works and items that can be used in daily life, such as teapots and cups.

His representative creative works are small-mouthed jars boasting crisscrosses at the bottom and the top, yet with the middle remaining glossy.

"I combined two kinds of clay. The middle part clay is without iron content while the top and the bottom adopt clay of high iron content, so the glaze cracked there and formed a unique pattern," Jin explains.

"Only 10 pieces among 300 work in the end," Jin says, providing a reminder of the great difficulty in producing a quality piece of Guan kiln work.