Introduction
Koreans started making pottery in the Neolithic Age. During the Three Kingdoms period (the kingdoms of Goguryeo, Baekje and Silla, from 37BC to 668AD), they began to make stoneware, followed by primitive celadon. As technology developed, Koreans found clay bodies which were able to resist high temperature, and thus started to build kilns. This development had shifted the center of the ceramics culture from earthenware to porcelain ware.
The development of Goryeo celadon roughly corresponds to the rise and fall of the Goryeo dynasty (918-1392). Goryeo celadon, in addition to reflecting the level of craftsmanship of the time, is an important reference to understanding Korean culture.
The research of the properties and development stages of Goryeo celadon has been difficult due to inadequate chronological data on celadon and a severe shortage of relevant historical records. However, many new findings have recently been developed as more kiln sites and historical remains are unearthed.
Among many types of ceramics (e.g. celadon, white porcelain, black porcelain, green-glazed pottery, and earthenware), celadon constitutes the main type of ceramics produced during the Goryeo period. Celadon is identified with a type of stoneware which contains a percentage of iron in the glaze recipe or clay body and is fired in a reducing atmosphere kiln. Based on design techniques, celadon wares may be categorized as with no decorative patterns, with intaglio designs, with relief designs, with inlaid designs, and with openwork designs. According to colorant, these ceramics may be classified into several types, such as with iron painting, with brown paint, with cinnabar (copper red glaze), and with copper pigment. There are no sufficient resources concerning when and how celadon was developed; views about the history of Goryeo celadon vary greatly. However, the following are some major statements which may be considered.
Choi, Sun-u: The evolution of Goryeo ceramics may be divided into seven stages according to the reigning monarch, i.e. emerging, exploring, pre-maturing, maturing, prime, zenith, and declining.
Chin, Hong-sup: The history of celadon may be divided into three phases: the formation of celadon, the zenith, and the prime of inlaid design.
Chung, Yang-mo: The history of celadon may be divided into early, mid, and late stages. The early stage may be further separated into two: the “dawn”/maturing period and the development period (from Emperor Taejo (918) to Emperor Yejong (1122). The mid stage is from Emperor Injong (1123) to Emperor Wonjong (1274), during which jadeite colors became the mainstream and the inlay design hit its peak. The late stage is from King Chungnyeol (1275) to King Gongyang (1392), during which the vessel shapes and the decorative patterns were deeply influenced by the Yuan dynasty - the former became functional, and the latter, diverse.
Kang, Kyung-suk: During the Goryeo dynasty from its founding to fall, the history of Goryeo celadon may be divided into four stages, that is, beginning middle, late, and end stages.
Yun, Yong-i: The history of celadon may be divided into three stages, i.e. early, mid, and late stages.
Choi, Kun: The history of celadon may be separated into five periods, i.e. emerging (9th - late 10th century), refining (11th century), peak (late 11th – mid 13th century), declining (late 13th - late 14th century), and spreading (late 14th - early 15th century) periods. Or, it may be separated into six stages according to genealogical and historical records of kiln sites.

Over the past decade, the research has been centered on the advent of Goryeo celadon and the chronology of inlaid celadon with the inscription "Gan-Ji (the sexagenary cycle)". Researchers on one hand have examined ceramics itself in a general manner, and on the other hand have endeavored to understand the social, economic, and cultural history behind ceramic wares. Lately, some have also been zealous in conducting scientific research of ceramic specimens. However, despite abundant number of celadon wares, the studies done so far only focus on some indicative sites. The correlation of any two kiln sites is still unclear; and the overall development and transition of celadon also remain vague because of insufficient textual research on ancient literature and paintings.
The Advent and Development of Goryeo Celadon
The early Goryeo period - the advent and development of celadon
The Chinese ceramics culture has had its influence on Goryeo celadon from the very beginning. There are many arguments made regarding the advent of Goryeo celadon. The two most important arguments are the theory of 9th-century (the Unified Silla period) appearance advocated by Yang-mo Chung, and the theory of 10th-century (the early Goryeo period) appearance supported by Lee, Jong-min. The theory of 9th-century appearance states that Koreans started making lead-glazed pottery and ash-glazed stoneware in the 7th century, and began to produce celadon in the 9th century in the southwestern coast of the Korean peninsula and part of the Gyeonggi-do area, when they acquired new kiln technology from China. The theory is mainly grounded in the recognition of the Bowl with a Pi-shaped Foot Ring (Bowl with Jade-Round Bottom). It indicates that Goryeo celadon appeared either in early or late 9th century, or early 10th century, with the influence of Yue-zhou kilns in China. Nevertheless, this argument has not been verified as no kiln sites or celadon wares within the said time span has been uncovered.
The theory of 10th-century appearance has two arguments. One stands for celadon appearing in the first half of the 10th century based on the findings of the Wonsan-ri kiln site in Pongchon County, where inscribed celadon wares from the third year (992 AD) and the fourth year (993AD) of the Chunhua reign were excavated. The other believes Goryeo celadon came into existence in the second half of the 10th century according to the investigation results of kiln sites at Seo-ri of Yongin-si and the Yonggye-ri kiln site in Gochang County, where broken roof tiles with the inscription “the second year of Taepyeong lmsul (1022)” were unearthed. Furthermore, North Korean academic scholars claim that the first celadon wares were produced around the 9th century, before the existence of the celadon with the inscription “the third year of Chunhua” discovered in the Wonsan-ri kiln site. They assert that Goryeo celadon wares were locally manufactured and were in the development phases during the 10th century. In other words, those academics trace the origin of Korean celadon from ceramics made in the late Unified Silla period.
Recently, researchers have been inclined to think that new kiln technologies were introduced from China after the mid- or late-10th century, by adducing chronological data uncovered in numerous historic sites and celadon samples with the inscription of “the third year of Chunhua” or “the fourth year of Chunhua” found in the Wonsan-ri kiln site in Pongchon County. It is believed that the development of Goryeo celadon advanced rapidly in the 11th century, when the political and social environment was stable and trading activities were active. During that time, amazing and diversified styles unique to Goryeo celadon were established in terms of type, shape, decorative pattern, and firing technique. The celadon glazes could be rendered with quality almost as high as that of Chinese celadon; the shape of the vessels was similar to that of Guan wares.
Meanwhile, some alternative rough celadon (green celadon) kiln sites were excavated in Kyungseo-dong and Haenam of Incheon. They were different from some of the above-mentioned sites in a manner that they produced rough celadon wares for local temples, officials, and nobles, while those in Gangjin and Buan were royal kilns. The operation of such kilns continued in the first half of the 12th century and gradually stopped in the late 13th century.
The middle Goryeo period - the peak of celadon
The firing technology of celadon reached its peak during the mid Goryeo period (from the 12th century to the first half of 13th century). The production included green-glazed celadon with line patterns, celadon with no patterns, celadon with inlaid designs, copper-red-glazed celadon, and celadon with brown paint. The manufacture of white and black porcelain was also on the move. However, the lacking of reliable sources of information and chronological data has made research difficult.
Here listed below are a few of the perspectives and research findings of the day. Choi, Sun-u believes that Goryeo celadon was booming in the first half of the 12th century, and it was then that jadeite celadon appeared. During that time, inlaying techniques and copper red were used in some designs; paste-on-paste and iron painting skills were more mature and diversified. From the mid 12th century to 1231 (the 18th year of Emperor Gojong's reign), Goryeo saw the prime of celadon with inlaid patterns, shook off the influence of China, and developed its unique inlaid celadon wares and inlaid white porcelain wares. Chung, Yang-mo stated that inlaid celadon didn’t hit its peak and image patterns didn’t come into view until the period from mid 12th century to the first half of the 13th century. Kang, Kyung-suk argued that it was during the period from 1147 to 1274 when inlaid celadon emerged, developed, and flourished. Yun, Yong-i asserted that the zenith of celadon during the mid Goryeo period was from 1100 to 1250. He said that jadeite celadon as well as skills of iron painting and inlay design appeared and developed in the first half of the 12th century. In the second half of the 12th century, jadeite celadon reached its prime time, and inlay techniques were more popular along with copper coloring, iron painting, and white porcelain. Yun believed that it was the first half of the 13th century that welcomed the zenith of inlaid celadon.
The second half of the 12th century was the period when Emperor Uijong (1147-1170) and Emperor Myeongjong (1171-1197) were on the throne. It was the time when the nobles of Goryeo began to lose their influence over social political power, as well as the time when Goryeo celadon developed from no decorations to inlaid designs. In the 13th century, while inlaid celadon continued to develop, Goryeo struggled and tottered under Mongolian influence for decades. By the 14th century, the quality of celadon slowly deteriorated, and Joseon Buncheong ware began to come into being.
The late Goryeo period - celadon with increased production volume but decreasing quality
Inlaid celadon wares prevailed through the ages starting from the time of the Mongol invasions (1231-1273) to the founding of Joseon dynasty (1392); yet their performance in glaze color, pattern, shape, and clay body gradually worsened. Those vessels were subsequently replaced by Joseon Buncheong ware. Overall speaking, this phenomenon may be explained by external factors, including Mongolians’ campaign, Japanese pirates’ attack, and the influence of Yuan dynasty ceramics, and internal factors, such as decreasing quality. The war, on one hand, helped ceramic culture to spread widely and celadon production to grow, but on the other hand caused the quality to go down.
The biggest controversial issue regarding celadon in the late Goryeo period is the manufacturing period of inlaid celadon with the inscription "Gan-Ji (the sexagenary cycle)". The research in such topic has had its importance when studying later-period Goryeo celadon, and this topic has remained to be widely debated till today.
Numerous researchers unanimously believe that inlaid celadon with the inscription "Gan-Ji” can represent celadon in the late Goryeo period. Yet they haven’t reached a consensus concerning the time when such celadon wares were produced. Some said it's the 13th century (1269-1295); some assumed it's the 14th century (1329-1355); and still some argued it's between the late 13th to the early 14th century.

Till now, many researchers still presume that it was the recession during the later Goryeo period that caused the quality of celadon to drop. However, they do not have any specific historic data to support their argument. There are also some who argued that “the interference from the Yuan dynasty” was the major reason. But I accept neither of the above statements.
The declining or spreading period of Goryeo celadon is supposed to correspond to the emerging period of Joseon Buncheong ware. Relative studies have captured only an approximate, not an absolute, timetable for the development of shape and pattern of Goryeo celadon wares. If the firing years of inlaid celadon with the inscription "Gan-Ji” indeed falls within the 13th century, as many have said, then a gap of at least 50 years will appear between such assertion and several excavated samples. Thus I believe that it is necessary to re-examine the firing years of inlaid celadon with “Gan-Ji” inscription. In this regard, two inlaid celadon wares fired around the mid of 14th and firing skills by referring to the excavation; and propose a new chronicle.
Conclusion and Future Prospects
The study of Goryeo celadon has made leaping progress through numerous academic surveys and different types of research. However, many more issues are to be clarified. For example, the relations between the development of Goryeo celadon and Chinese ceramics need to be elucidated through research; the connections between Chinese kiln structures and manufacturing technology versus the production system and distribution structure in the Goryeo dynasty need to be illuminated through comparative studies, or through research into the literature excavated from under the sea.
Moreover, Goryeo celadon's market areas and production sites are also subjects to be looked into. In recent years, an increasing number of Goryeo celadon wares have been found in China, Japan, and even Mongolia, Taiwan, and the Philippines. It is necessary to actively study trade and diplomatic exchanges among these areas spurred by Goryeo celadon. Meanwhile, understanding the usage and users of different types of vessels will help ascertain their functions and culture, as well as their social and economic importance. The study of the development of decorative patterns also cannot be ignored. These are all important topics to be examined deeper.
To fully understand Goryeo celadon, systematic and rational archaeological investigation of kiln sites is a requisite. Such investigation and chronological analysis of historically-significant kiln sites in Gangjin, Buan, and Haenam in particular will no doubt be the gospel for Goryeo celadon research.