Longyao

Longyao, also known as Changyao, is a semi continuous ceramic firing kiln. It is built on a certain slope and named after the reclining dragon.

Longyao

It is a form of kiln in our country. Most of them are built on the slopes of the south of the Yangtze River. First discovered in Shangyu, Zhejiang Province, it is a kiln site of Shang Dynasty. Kiln long strip, built by the hillside, from the bottom up, like a dragon like snake, hence the name. Also known as Snake Kiln, centipede kiln.

In 2009, the ancient kiln site, which was discovered by villagers before liberation, can be traced back to the end of Tang Dynasty and the beginning of Ning Dynasty.

In 2013, in the archaeological excavation of Nanyao in Jingdezhen, Jiangxi Province, the longest remains of Longyao in Tang Dynasty were found.

Development history

Longyao, also known as Changyao, is a semi continuous ceramic firing kiln. It is built on a certain slope and named after the reclining dragon.

Longyao appeared in Shang Dynasty. In this period, Longyao not only fired hard pottery with printed patterns, but also fired primitive celadon, which is commonly known as "co firing of ceramics in the same kiln". In the late Eastern Han Dynasty, the co firing of ceramics in the same kiln ended, and Longyao, which specialized in firing porcelain, appeared. After chemical analysis and physical determination, the fragments of celadon unearthed from the Eastern Han Dynasty kiln site in Shangyu, Zhejiang Province, have reached the standard of porcelain. The appearance of porcelain in the Eastern Han Dynasty is directly related to the improvement of Longyao. In the early period, the length of the dragon kiln was generally more than ten to twenty meters. In the Song Dynasty, the length of the dragon kiln was 50 to 60 meters, and even 70 to 80 meters in some areas. It could hold 20000 pieces of porcelain at a time, which played an important role in the development of porcelain at that time. With the gradual growth of Longyao, the inclination and structure of each dynasty were constantly improved, so that the firing effect of Longyao was constantly improved. In song and Yuan Dynasties, there was a kind of Longyao in which multi-channel fire retaining wall was built inside the kiln, which was divided into several small rooms, and fireworks holes were set at the bottom of the fire retaining wall, so that the rooms were connected, that is, the so-called "sub room Longyao". Up to now, Longyao is still used to make ceramics in some areas of South China.

From Shang Dynasty to Ming and Qing Dynasties, Longyao was mostly built in southern China. Before the Ming Dynasty, porcelain was widely used in southern China, such as Jiangsu, Zhejiang, Guangdong, Fujian, Jiangxi and Hunan. Until 2013, there are still a few dragon kilns in the south of the Yangtze River and parts of Southeast Asia in China.

Kiln structure and schematic diagram

The kiln chamber is divided into kiln head, kiln bed and kiln tail. A long tunnel kiln is built on the slope or mound of earth, which forms an angle of 10-20 ° with the horizon. The angle of kiln head is about 20 degrees, the middle part is about 15 degrees and the rear part is about 11 degrees. There is a preheating chamber at the kiln head, and there is usually no chimney or short chimney at the kiln tail, because the dragon kiln itself plays the role of chimney. The length of the kiln is about 20-80 meters, the width of the kiln is about 1.5-2.5 meters, and the height is about 1.6-2 meters. The cross-sectional area of the kiln head is the smallest, which is convenient for heat concentration and combustion at the beginning of the kiln. The maximum cross-sectional area is in the middle of the kiln, and the kiln tail is larger than the kiln head but smaller than the middle of the kiln. There are many rows of firewood feeding holes with a diameter of about 0.15m on the upper part of both sides or on the top of the kiln. There are two kiln doors on both sides of the kiln. The structure of the whole kiln is simple, the construction cost is low, and the arch brick with strict size is not needed. During the long kiln operation, all the kiln doors are closed after the green bodies are packed in the kiln room. First, the kiln head is fired, and then the firewood is poured from the front to the back in order. The highest firing temperature is 1300 ℃, and the reduction flame can be controlled.

main features

The natural ventilation mode is adopted in the Longyao kiln, with miscellaneous firewood, pine branches and other plants as fuel, and the flame in the kiln flows parallel to the bottom of the kiln. In addition, this kind of kiln is built on the hillside, which has large flame pulling force, fast heating, fast heating and fast cooling; it can be burned quickly, and it can also maintain the reduction flame of firing celadon. So it is said that Longyao is the cradle of celadon. Shadow green, black glazed porcelain and so on are mostly fired in the dragon kiln. At the same time, the loading and burning area is large and the output is high.

① The inclined setting of kiln body itself plays the role of chimney. The geometric pressure head can overcome the resistance of material stack, so that the kiln can operate near zero pressure and reduce the phenomenon of air leakage and suction.

② As the combustion section moves back gradually, the heat of flue gas and product is effectively utilized, the heat loss is significantly reduced, the combustion temperature is increased, and the production cycle is shortened.

③ Because of the fast firing, the heat dissipation and storage of the kiln body are not large, the heat consumption per unit product is less, and its thermal efficiency is close to that of the tunnel kiln.

④ The simple and crude structure of the kiln makes the labor intensity of loading and discharging the kiln high, and it is difficult to realize mechanization and semi automation.

⑤ The temperature and atmosphere in the kiln fluctuate greatly, and the large products and dense industrial ceramics are prone to cold cracking. Sometimes due to insufficient heat preservation under the firing temperature, the firing quality is affected.

Representative sites

Dehua dragon kiln

Longyao is a form of kiln in China. It is mostly built on the slope of Jiangnan area. It was first found in Shangyu, Zhejiang Province, and is a kiln site of Shang Dynasty. The kiln is a long strip, built on the hillside, from bottom to top, like a dragon like a snake, so it is also called Snake Kiln and centipede kiln. The kiln chamber is divided into kiln head, kiln bed and kiln tail, which is built on the hillside.

Dehua dragon kiln was first built in the middle and late Tang Dynasty. In the Northern Song Dynasty, the structure was more reasonable. It was generally 20 meters long with a slope of 10-28 degrees. It was composed of kiln head, kiln chamber and kiln tail. The kiln head was equipped with fire chamber. The kiln chamber was divided into several items (sections). There were several kiln doors on both sides of the ladder passageway to install the product passageway. Firewood feeding holes (fire holes) are arranged symmetrically at the kiln walls on both sides of each section. A fire wall is set at the end of the kiln, a smoke hole is set at the bottom of the wall, and a smoke Lane is set behind the wall, commonly known as a chimney. It is 3 meters high and 0.4 meters wide, and its length varies according to the kiln body. Make full use of waste heat by using the principle of slope height difference and flame rising naturally.

In the Northern Song Dynasty, the body of the long kiln was narrow and short. During the Southern Song Dynasty, the kiln body was widened, the kiln body became longer, the kiln bed was covered with sand, and the slope was smaller. This kind of kiln was still used in Ming and Qing Dynasties.

After the founding of new China, Dehua kiln was still dominated by dragon kiln. In the 1960s, there were nearly 100 long kilns in the county, most of which were built on hillsides. They were about 43 meters long and divided into 32 meshes. The kiln head was 6 meshes, 1.2-1.7 meters high, 1.1-1.7 meters long and 1.2-1.6 meters wide. From the middle of the kiln to the end of the kiln, they were 26 meshes, 1.85-2.5 meters high, 1.8-2.2 meters long and 2.4-2.6 meters wide. A fire chamber is set at the kiln head. A firewood feeding hole is symmetrically placed on both sides of each kiln chamber, which is also a fire color observation hole. The hole is about 0.15 × 0.2m. Finally, the gate wall (fire wall) is set up, and nine smoke holes are placed at the foot of the wall. The inclination is about 25-27 degrees. The structure is reasonable, and the loading and burning capacity is large. The temperature rise is moderate and uniform, and the yield is high. At the same time, there are few accidents and the operation is easy.

Longyao is a kind of firewood kiln. Because it uses firewood as raw material, it has been basically withdrawn from the historical stage and replaced by electric kiln, oil kiln, liquefied gas kiln and natural gas kiln.

Nanfeng ancient stove

Nanfengzao was built in the Zhengde period of Ming Dynasty (1506-1521). With a history of nearly 500 years, it is a national key cultural relic protection unit. It is the oldest wood burning dragon kiln still in use in the world. The kiln is built close to the mountain, with a total length of 34.4 meters and an inner length of 30.87 meters. It is like a giant dragon falling from the sky, so local residents call it "dragon kiln". However, the residents of Shiwan also call Longyao "kitchen", because the place where the wood is burned at the kiln head is like the kitchen where the wood is burned at home in the old days. Moreover, the potters rely on Longyao products to support their families. They think Longyao is as important as the "kitchen" at home. In addition, the stove mouth of the Longyao is facing the south, and the banyan trees at the end of the stove are shady. It is cool every summer, so it is called "Nanfeng stove".

In August 2013, the overhaul of Nanfeng guzaolong kiln began, which has lasted for one year.

On August 23, 2014, the fifth Longyao firewood burning Culture Festival was opened at the Nanfeng ancient ceremony in Shiwan. The two overhauled Longyao were re ignited. The first batch of kilns are the works of more than 50 potters from Nanfeng guzao Park and arts and Crafts Association. Because of its unique oxidation atmosphere, the products fired by Longyao will have glaze effect that other kilns can't achieve.

Because Longyao is a high temperature firing product, the highest temperature can reach more than 1300 degrees Celsius. Due to the factors of thermal expansion, cold contraction and high temperature melting, the Longyao kiln will rot or deform, and the back arch of the kiln will collapse to varying degrees, so it needs to be overhauled after a period of use.

In order to overhaul the kiln, the inner wall and the back arch of the kiln should be removed, while the outer wall and the red sandstone and rammed earth beside it should be preserved, which is a historical site left by the Ming Dynasty. After that, it is necessary to re open the line and position the Longyao according to the previous understanding. After fixing the position, the workers should be organized to lay bricks.

Gaozao

Gaozao was built in Wanli period of Ming Dynasty, which was later than nanfengzao in the same park. Gulong kiln, which has been used since Ming Dynasty, has a history of more than 400 years.

The shape and slope of the kiln are similar to that of the south wind stove. The kiln faces due south. There are four kiln gates on the left and three on the right. The structure of the kiln is like a tunnel with round arch roof, which is made of small sand bricks. The overall length of the kiln is 38.25m. The width of the kiln mouth, middle section and tail are 1.85M, 2.25m and 2.2m respectively. The inner height is 1.80-1.95m. The thickness of the top of the kiln is about 0.25m. The original 42 rows of fire holes on the kiln surface were changed to 33 rows after the founding of the people's Republic of China. There are 5 fire holes except 3 at the kiln entrance. During the Ming and Qing Dynasties, the kiln was a professional dragon kiln, which was famous for its pottery industry. It is important to study the history of pottery making and ancient calcination technology

Chinese PinYin : Long Yao