I · THE OBJECT · BRITISH MUSEUM
Korean Goryeo Celadon
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When a twelfth-century Chinese writer ranked the world's ceramics, he placed Korean celadon above everything made in China. The inlay technique that earned that praise was invented in Korea and remained uniquely Korean.
At a glance
- Period
- Goryeo dynasty, 918–1392
- Peak production
- 12th–13th century
- Technique
- Sanggam: white and red clay inlaid into leather-hard body
- Glaze colour
- Blue-green, from iron oxide in reduction firing
Look closer
The inlay happens before glazing
Sanggam decoration is not painted on. The potter incises or stamps a pattern into the clay body when it is leather-hard — dry enough to hold detail but not yet fired. White slip and sometimes red slip are pressed into the recesses, then the surface is scraped smooth so the inlay sits flush with the body. Only after this is the celadon glaze applied. The glaze is thin enough that the contrasting colours remain visible beneath it, creating a design that cannot wear off because it is locked into the clay itself.
Reduction firing controls the colour
The blue-green colour comes from a small amount of iron oxide in the glaze, fired in a reducing atmosphere — that is, in a kiln starved of oxygen. In reduction, iron turns grey-green or blue-green rather than the brown or amber it would produce in an oxidising atmosphere. The exact shade depends on the iron content, the kiln temperature, and how completely reduction is maintained. Goryeo potters achieved a range of tones, from pale jade to deep sea-green, all from the same basic chemistry manipulated through firing.
Crackle was deliberate
Many Goryeo celadons show a fine network of cracks in the glaze. This crackle forms because the glaze and the clay body contract at slightly different rates as they cool. In some ceramic traditions crackle is a defect to be avoided, but Goryeo potters appear to have valued it. The crackle is often emphasised by the way light catches it, and on pieces that have been buried or used for centuries, the cracks have darkened, creating a delicate web across the surface that many collectors prize.
The story
Celadon — high-fired stoneware with a green glaze — was first developed in China, and Korean potters learned the technique during the ninth and tenth centuries. By the early Goryeo period they were producing celadons that matched Chinese work in technical quality. But sometime in the twelfth century, Korean potters invented something new: sanggam, the inlay technique that would define Goryeo celadon and distinguish it from everything made elsewhere.
The process required patience and a steady hand. The vessel was thrown or moulded, then allowed to dry to a leather-hard state. At that point the potter incised or stamped patterns into the surface — chrysanthemums, cranes, clouds, willow branches, geometric borders. White clay slip, and sometimes iron-rich red slip, was pressed into the grooves and left to stiffen. Once firm, the surface was scraped level, leaving the contrasting clay visible only in the recessed pattern. The piece was then coated in celadon glaze and fired.
The result was decoration that sat beneath the glaze rather than on top of it, protected and permanent. The white inlay stayed crisp under the translucent green, creating a contrast that was subtle but unmistakable. Some pieces combined incised line with stamped motifs; others used inlay to fill large areas, almost like marquetry in clay.
Chinese connoisseurs noticed. Xu Jing, a Song dynasty official who visited Goryeo in 1123, wrote that Korean celadon was "first under heaven" — a remarkable statement from a representative of a culture that had invented celadon and refined it over centuries. He was writing about pre-inlay Goryeo ware, admiring its colour and finish. By the time sanggam became widespread in the mid-twelfth century, Korean potters had added a decorative technique that China never mastered.
Why the technique remained uniquely Korean is not entirely clear. Chinese potters certainly knew about it — trade and diplomatic exchange were constant — but no Chinese kiln produced sanggam celadon successfully. It may have been that the technique required specific clay bodies, or firing schedules that did not suit Chinese kiln designs. It may also have been that Chinese taste moved in other directions. Whatever the reason, sanggam stayed Korean.
Production continued into the thirteenth century, but the Mongol invasions of the 1230s disrupted the kilns. Some production resumed, but the technical peak had passed. By the fourteenth century, as the Goryeo dynasty weakened, celadon quality declined. The Joseon dynasty that followed in 1392 favoured white porcelain over celadon, and the sanggam tradition faded. It was not successfully revived until the twentieth century, when Korean potters reconstructed the technique from surviving examples.
Why it mattered then
Celadon was luxury ware, made for the court, aristocratic families, and Buddhist temples. Goryeo was a deeply Buddhist state, and many of the finest celadons were made as temple furniture — incense burners, water droppers for grinding ink, ritual vessels. The inlaid decoration often carried Buddhist motifs: lotus flowers, willow branches, cranes symbolising longevity. The technique also signalled sophistication. Goryeo maintained close diplomatic and trade relations with Song China, and Korean elites were highly literate in Chinese culture. To produce ceramics that Chinese connoisseurs ranked above their own was a matter of both craft pride and cultural confidence. It demonstrated that Korea was not merely imitating Chinese models but innovating within a shared tradition. The labour involved also mattered. Sanggam required more steps and more skill than simple glazing, and the risk of failure was higher. A vessel that cracked during drying, or where the inlay pulled away from the body during firing, was unsalvageable. High-quality inlaid celadon was expensive, and owning it marked status.
Why it matters now
Goryeo celadon is now regarded as one of the great achievements of Korean art, and sanggam inlay is taught as a distinctively Korean contribution to world ceramics. The twentieth-century revival of the technique, led by potters like Yu Geun-hyeong, was part of a broader effort to recover and preserve Korean craft traditions after the colonial period. Museums in Korea and internationally hold significant collections, and the finest pieces command high prices at auction. The South Korean government has designated several Goryeo celadons as National Treasures, and the tradition is part of the case for Korean ceramics as a field deserving sustained scholarly attention, not merely as a regional variant of Chinese work but as an independent tradition with its own logic and innovations. The technique also remains a working tradition. Contemporary Korean potters continue to make sanggam celadon, some working in close imitation of twelfth-century forms, others adapting the inlay method to modern shapes and sensibilities. The fact that the technique was never successfully copied elsewhere has become part of its identity: it is legibly Korean in a way that few other ceramic techniques are.
The surprising detail
During the Japanese invasions of Korea in the 1590s, many Korean potters were forcibly taken to Japan. These potters and their descendants played a central role in developing Japanese porcelain and stoneware traditions. Arita ware, which became one of Japan's most celebrated porcelain styles, was founded by Yi Sam-pyeong, a Korean potter brought to Kyushu. Satsuma ware, another major Japanese tradition, was established by Korean potters as well. Some of their descendants in Japan have continued to use Korean names across generations to acknowledge their origin. The irony is stark: a ceramic tradition that Korea could not sustain through political upheaval helped to establish new traditions in the country that disrupted it.
What is disputed
The exact date when sanggam inlay was invented is not known. It appears to have developed sometime in the twelfth century, but whether it emerged gradually or was the innovation of a particular kiln or potter is unclear. The reasons why the technique did not spread to China are also speculative — contemporary Chinese sources do not explain why they did not adopt it, so modern explanations rest on inference from technical and economic factors.
Remember this
Sanggam inlay — clay pressed into clay beneath the glaze — was invented in Korea, admired in China, and never copied successfully elsewhere.
Test yourself
Why would a technique as admired as sanggam inlay not spread to China, where celadon itself was invented and potters had centuries of experience?
Several factors likely combined. The technique may have required specific clay bodies or firing schedules that did not match the setups of Chinese kilns, which were optimised for different wares. Chinese taste in the Song and Yuan periods also moved toward other innovations — underglaze painting, for instance — so there may not have been strong demand for inlaid decoration even if the technique was understood. It is also possible that the process was considered too labour-intensive relative to the visual effect, or that Korean potters guarded certain details of the method. The broader lesson is that techniques do not transfer automatically even between cultures in close contact. Adoption depends on fit: with existing infrastructure, with aesthetic priorities, and with economic logic.
Go deeper
Image: Steve46814, CC BY-SA 3.0. Licence: CC BY-SA 3.0. Source.