Early celadon

Pottery and celadon had been introduced into the Korean peninsula in the Three Kingdom age. Demand for higher quality porcelain increased as the Goryeo Dynasty emerged. Along with the development of tea culture and Buddhism, wares based on traditional and southern China (Song dynasty) porcelain began production in Goryeo .^[6] Most of the pottery made in this era are the kinds that are called haemurigup celadon and green celadon (low-grade)

11th century

As the celadon techniques of the Song dynasty reached its pinnacle, much effort was made inside Goryeo to reproduce the turquoise coloring of these Chinese porcelain. A lot of kilns were made throughout the kingdom, leading to a variety of celadon being made. High grade celadon were made in order of the capital, and low grade celadon were made by the requests of temples, offices and local families of provinces.

Though Chinese influences were still existent, Goryeo styled shapes and decorations emerged in some porcelains. These are characterized by the utilization of light curves and a serene, elegant feel. Decoration techniques such as relief carving, intaglio carving, iron oxide glaze, openwork became in use. The sanggam inlaying also started at this age.

12th century

Celadon gourd-shaped kettle : This work is balanced and gives a sense of stability. It is a typical pure celadon of the 12th century. The glaze and the foundation soil are translucent, clean, grey-green, and harmonious.^[7]

The 12th century is considered as a zenith of Goryeo celadon, especially in its special color and harmony. The pure celadon made in this age had thin glaze coating that exquisitely reflected the jade color, called bisaek. They also had a great level of structural balance and elegance.^[8] There are records describing celadon of this age as world best.^[9]

Jinsa "underglaze red", a technique using copper oxide pigment to create copper-red designs, was developed in Korea during the 12th century, and later inspired the "underglaze red" ceramics of the Yuan dynasty.^{[10][11][12][13]}

Post-12th century

Maturation of the aristocrat society due to events such as the coup of military officers leads to an increasing favor for extravagantly decorated porcelain. Inlaying techniques reach its height and opens a second zenith of Goryeo celadon. Other types of porcelain develop as whitening, iron oxide glaze, copper oxide glaze came in use. With the decrease of Chinese influence, Goryeo celadon acquires a more native shape, in unique patterns and decorative shapes.^[14] Thin, transparent glaze used to show the inlaid designs led to development of a crackling cooling pattern, called bingyeol (craquelure).

13th century

After the Mongolian invasion in 1220, social and economic confusion had caused the general quality of Goryeo celadon to decline. Influence of Yuan dynasty is seen throughout the porcelain produced in this time.^[15] Though the celadon industry remained, overall density of expressions and smoothness decreased and the color and harmony are also diminished. This decrease in its beauty continues as the Goryeo dynasty recedes.^[16]

14th century

In the late 14th Century, the Kilns of Gangjin and Buanyo were attacked by Japanese pirates and closed. Inland kilns replace them, putting an end to the age of celadon. Though new characteristic shapes and designs appear, they are utilitarian instead of being elegant and restrained, as Goryeo celadon in its zenith did. One of these new types of porcelain is called buncheong.

20th century

A revival of Goryeo celadon pottery began in the early 20th century. Playing a leading role in its revival in South Korea was Yu Geun-Hyeong, a Living National Treasure whose work was documented in the 1979 short film, Koryo Celadon. North Korean potter U chi-son separately recreated Goryeo celadon pottery.^[17]

Inlay technique

For the inlay technique, several patterns are engraved on the surface of metal, clay, wood, etc. Other materials such as gold, silver, jewelry, bone are inserted in the same shape. This traditional decoration technique started to be applied in porcelain in the Goryeo dynasty. Purple (black) and white clay were used to show the patterns.^[18]

A pattern is engraved on celadon with a knife and covered with purple and white soil. When the soil dries, the overflowing mud is wiped off, remaining only in the carved areas; thus, a white or purple pattern will appear. When it is baked after painted with glaze, the white soil appears as white and the purple as black, and this pattern is seen through the glaze.

Differences from Chinese celadon

Cracks on Goryeo celadon

Glaze of Goryeo celadon had a definite composition starting from the 11th century to the 15th century. It contained a lot of calcium in composition, with 0.5% of manganese oxide, which was more concentrated than glaze used in Chinese celadon. Also in the case of Chinese ceramics, there is enough time for nucleation-crystal growth, so it takes jade color. But the kilns in Goryeo were smaller than that in China, so the firing and cooling process took place quickly. Therefore, minerals in soil such as anorthite or wollastonite have no time for nucleation-crystal growth. This results in the color of celadon being closer to the gray side. In Goryeo celadon, quartz, black particles, bubbles, cracks can be observed too.

The technical contribution of the celadon is that it has a white, black, or gray inlay to emphasize the grayish green color. In addition, when they used white inlay, the glaze was intentionally composited to make cracks. Light was scattered by the small cracks. So degrees of color of the celadon depend on the location of view. Pattern such as of the Koryeo celadon