Cracking a Porcelain Puzzle

By Bai Shi

Science and technology have ascended to an unprecedented level in modern life, but the ancient study of ceramics continues to perplex some of its most advanced experts.

Celadon, a type of ceramic ware featuring a glass-like glaze and a grey or greenish color, is one example of an artistic material with a mystical quality. The kind of porcelain was invented in Longquan, east Chinas Zhejiang Province, and spread to other regions around the world. Celadon ware with cracked-ice glaze is a highly valuable work that requires complicated production techniques. The craft had disappeared in China for about two centuries until ceramics master Chen Tangen revived the cracked-ice celadon technique in 2002.

In September 2009, the United Nations Educational, Scientific and Cultural Organization(UNESCO) inscribed the traditional firing technology of Longquan celadon on its Representative List of the Intangible Cultural Heritage of Humanity. It is the only porcelain craft to have made the world-famous list.

Precious heritage

In Chinas long history of porcelain crafts making, celadon occupies an important place. Longquan has been a ceramic center in China ever since the fifth century.

The golden era of Longquan celadon occurred during the Song Dynasty (960-1279). Countless ceramic works made in Longquan were exported to many regions in Asia, Europe and Africa, winning worldwide acclaim in the art market. Over 360 ancient celadon kilns, known to historians as Longquan Kilns, have been constructed in the city. A series of historical records detail the production of celadon, including the highest quality and largest amount of sales.

However, due to the rise of blue-and-white porcelain in China and the seclusion policy of the Ming Dynasty (1368-1644), the export of Longquan celadon dropped sharply and the special kilns for former imperial households of the Song Dynasty were closed down. The remaining kilns changed to make more common but lower-quality wares for local markets. As a result, the technologies and skills related to classical celadon were gradually lost as the product went out of fashion. Only a collection of rare celadon antiques remained.

Rebirth

Chen Tangen was born into a ceramics artisans family in Longquan in 1949.

Beginning in his childhood, Chen Tangen learned the craft from his father.

In the 1950s, many foreign experts who visited China inquired where they could find a type of ceramic ware called xue la tong. Chen Wanli, a well-known ancient porcelain expert at the Palace Museum, then identified it as Longquan celadon.

The long history of Longquan celadon was thereafter rediscovered as one of the most important porcelain products in ancient China. Its glittering green color and cracked glaze once again captivated art lovers around the world.

After hearing of the trend, the then Premier Zhou Enlai told the Light Industry Ministry to restore the production of Longquan celadon as soon as possible. The Longquan Kiln and four other well-known ancient kilns were put back into production in 1957.

Uncovering mystery

In 1964, Chen Tangen went to work in the state-owned Longquan Ceramics Factory. In the ensuing four decades of his porcelainmaking career, Chen Tangen saw the revival of Longquan celadon first hand.

The most unique feature of celadon is undoubtedly its vibrant glaze. “To create the beautiful color, an artisan must first experiment countless times. There is no shortcut,”said Chen Tangen.

Over the past several decades, Chen Tangen collected soil materials in dozens of places in Longquan. He conducted firing experiments using different techniques, and after hundreds of tests and adjustments, he successfully produced the lavender grey and plum green glaze out of two ancient kilns. While in the process of seeking traditional celadon technology, Chen Tangens achievement was uncovering the biggest mystery of celadon in the Song Dynasty: cracked glaze.

In the Song Dynasty, Longquan celadon was famous for two kilns, known as ge kiln and di kiln. Ge kiln was used primarily for imperial households while di kiln produced wares for average people. Celadon wares of the ge kiln are more precious thanks to their superb firing technology and artistic shape. Among the glaze types of ge celadon, the cracked-ice glaze stands out. Its exterior looks like a crack on the surface of a piece of ice. Nearly 1,000 years after the beginning of the Song Dynasty, many ceramic artisans attempted to recreate the cracked-ice glaze, but the technique was so complicated that none of them succeeded.

In 1996, Chen Tangen made up his mind to solve the mystery. “The first difficulty of firing cracked-ice celadon is to precisely control the proportion of base and glaze materials,” Chen explained. “Even a tiny error will result in failure.”

“The thickness of the glaze is also important. The cracks wont form if the glaze is too thin, and they will collapse if the glaze is too thick,” Chen Tangen continued.

Furthermore, the artisan said, the carbon monoxide and temperature control during the firing stage directly affects the glaze. In short, the artisan must have strict and accurate control over every step of the process.

Chen Tangen did not give up on his goal, even after 300 failed experiments. “After every failure, I would examine the steps I took and summarize my experience. As a result, I moved a bit closer to success each time,”Chen added.

One day in 2002, Chen Tangen reduced the kiln temperature to 100 degrees centigrade and slowly opened the kiln as usual. He heard a cracking noise from inside the kiln, and he saw on the surface of a ware appeared delicate cracked-ice texture, indicating the fantastic cracked-ice celadon was eventually reproduced successfully. A consummate technology that was lost for nearly 1,000 years was thereby recovered in Chen Tangens hands.

Needed innovation

According to Chen Tangen, the quality of todays Longquan celadon has reached the top level of that of the Song Dynasty. However, he stressed that ceramic craftsmen must continue to seek innovation and breakthroughs.

Due to the limits of ancient technology, the celadon wares from the Song Dynasty were small. The high temperature during firing tended to make celadon ware deform and sag. For this reason, there was a saying in Longquan: “The bigger the ware, the more likely it will fail.”

Over decades of research, Chen Tangen has adopted new formula to make celadon. He improves the processing technique of glaze to enhance its stability. Even the best celadon teapots in the Song Dynasty were merely 20 centimeters high, while Chen can make a 48-centimeter-high teapot, and a 1.4-meter-high vase.

With advancing technology, China, Japan and South Korea can produce celadon porcelain. Unlike Longquan, most of the other celadon wares are created with artificial chemical materials during processing. But in Longquan, artisans refuse to add artificial materials to fire celadon. “We stick to our traditional method,” Chen Tangen said.

Though Chen Tangens output is low (not more than 20 pieces of wares for each firing) the quality and value are high. He said Longquan celadon has the best reputation, even though it is not the most expensive of its kind.

“The unique glaze of Longquan celadon is due largely to local earth resources. The soil is our limited treasure, so we must cherish it. Thats why we dont exploit the earth on a large scale for mass production,” Chen Tangen said. “I hope the beautiful celadon as well as the natural environment of Longquan can be preserved for future generations.”n