Primitive celadons had been discovered all over China but concentrated in Zhejiang province. The earliest examples can be dated to the 3rd century B.C. in the late Zhou period. Similar vessels have also been found in Han tombs. They often resemble ritual bronze vessels, and the glazes tend to be uneven, imperfectly fired and brownish yellow in color.
The Yue wares were first produced in the Eastern Han period (1st – 3rd c.) in Hangzhou. In these earliest wares the body is a light grey between stoneware and porcelain, and the glaze varies from light olive to green. Yue ware developed further until it reached its peak from the Tang dynasty to Song dynasty. Mise (secret/forbidden color) ware is a variety of Yue ware first made for royal use in the Wuyue Kingdom (10th c.) of the Five Dynasties period, which is highly vitreous and renowned for their clear colors. Generally, glazes in this period transitioned from grey and olive to mostly green, and carved decoratioons depict a range of motifs from animal, floral to Buddhist. In the Tang dynasty Yue wares were a staple export, and fragments have been found in places as far as the Persian Gulf. Yue wares were found in temples and tombs in Japan and Korea, and arrival of Yue potters is likely to have helped the development of Koryu celadon in the 11th century.
Ru wares were produced in northern China, specifically commissioned for the imperial court in the Song dynasty (10-13th c.), and were considered the first among the “Five Great Kilns” in that period. Ru wares have simple, sometimes angular shapes. Some were left plain, and others decorated with elaborated carving of floral or animal motifs. The wares tend to be fully glazed and fired with tiny “sesame” stilts. The glaze is applied in several layers and differ in color, from green to sky blue to extremely pale blue. In order to imitate the appearance of jade, a thick texture “like lard dissolving” is desired. Ru wares were and stay very rare, since they were only in production for several decades at the end of the 11th century or start of the 12th century. The scarcity prompted attempts to reproduce these extremely valuable wares. They were imitated in Korean shortly after initial production, and Yongzheng Emperor (1723-35) of the Qing dynasty ordered potters in Jindezhen to copy Ru pieces from the imperial collection. For long the copies have been confused with the originals.
The Guan (official) kilns were established in Hangzhou under direction of the Song court after they fled from northern invasion and lost access to the Ru and Jun kilns. Production is likely to have started after peace was largely restored in 1141. Guan ware has thin (1-3mm) body and thick (0.5-2.5mm) glaze applied in several layers, and the glaze can become thicker than the body. Since they are reduction fired, the bodies appear rather dark for their iron content (3-5%). Crackled glaze is common in Guan wares, which could be unintentional or deliberate, but regardless became highly desired later and frequently imitated. The best wares have wide crackles on greyish blue glaze, followed by those with denser crackles and in brown, green, or gray. Crackling is due to the glazes contracting more than the bodies in the process of cooling, and the low silica level in Guan wares contributes to their crackles. The multiple layers of glaze can develop independent crazing systems, enhancing the depth of the glaze. The wares were often stained to emphasize the crackles, though they also become darker through use or burial.
Longquan ware was produced from late Song to the Yuan and Ming and in such large volume that it eclipsed earlier celadon for a long time. These mass produced wares tend to be in simple shapes, sometimes with carved or molded decorations that are less elaborate than earlier examples. Their more austere aesthetics seems to reflect the new idea about classical refinement at the Song court. The clay has high iron content, and exposed clay turn red brown in the cooling process when fresh air is let in after reduction firing, turning the iron into red iron oxide. The level of standardization is high, though the color of the glaze varies from blue, jade green to olive and gray. In earlier wares the presence of air bubbles and unmelted particles create a softly glowing effect, and later wares in the Ming dynasty are transparent due to higher firing temperature. The first layer of glaze is applied before the bisque firing, and more layers are applied and refired to a high temperature (1230-1290°C). Longquan ware was exported along all trade routes in central, southern and south-east Asia, and along the African east coast. They were exported in large numbers to Japan, and several Japanese classifying terms like kinuta (pale bluish green wares), tenryuji (pea green wares), and shichikan (clear water green wares) became widely used. Towards the end of the Song period, the high demand made it difficult to maintain high production standards. Wares became larger and thicker, which helped surviving long distance trade routes. The peak of exports was reached in the Ming dynasty, before production declined due to competition from blue and white wares in Jingdezhen.
Traditional Korean celadon was first produced and peaked in Koryu dynasty. Though high-fire green and brown stoneware was already being produced, the earliest “true” celadon wares were made in the end of 10th century AD. The close connection between Koryu wares and Chinese wares is apparent from the presence of Song wares in Koryo tombs. Yue wares produced in Zhejiang are likely to be a direct influence, as is shown by records of exchange of objects and potters between the regions. In early 12th century, Koryu ware saw a golden age marked by development of an original style, significant improvement in technique, and introduction of inlaying. Chinese forms and styles were adjusted to fit Korean taste, and inlaid wares became a central style. This prosperity continued into the first quarter of 13th century, and the decline in quality began before the Mongol invasion in 1231, which halted production completely. After work resumed in late 13th century, quality dipped further due to the impact of the war and Mongol occupancy. After the fall of Koryu dynasty in the end of 14th century, manufacturing technique for celadon was lost until it was rediscovered in the 1950s.
Glazes in Koryu celadon tend to resemble those in Longquan celadons. Due to imperfections in technique, they tend to be more varied in color, ranging from olive, green, to blue. Other features include a purple tint caused by the iron content in glaze or body, and brownish discoloration caused by accidental oxidation when the reducing atmosphere wasn’t maintained. Koryu potters used these properties to accentuate their designs, as the discoloration and running often produced a shading effect in vessels with relief, carved, or molded decoration.