The great majority of ceramics in this category are green-glazed or “celadon” wares, which is the most representative kind of ceramics produced during the Goryeo dynasty (918–1392). While in Korea this type of ceramic is called "cheongja" - meaning blue-green wares – the term “celadon” has been used in the West and likewise refers to the green colour of these wares.
It is assumed that the early production of celadon wares was instructed by potters from China, from the Yue kilns in present-day Zhejiang Province. By the 10th century, Korea produced its own celadon wares. The typical green colour was attained by applying a feldspar glaze with little iron content to the refined stoneware body and firing in a reduced oxygen atmosphere. The most remarkable results were achieved in the 12th century, a smooth glaze with a vibrant green colour, also known as “bisaek” – jade colour. Celadon ceramics were decorated by incising, carving, press-moulding and inlaying, by painting the surface with iron and copper oxide or gold, or by applying layers of red ocher and white slip. Animal, fruit and plant shapes were most popular. The inlay decoration technique, called “sanggam,” counts as one of the major accomplishments of Goryeo artistry and is displayed in great variety in the objects in this category. Many of the celadons the collection are tea wares, which is closely related to the development and proliferation of tea culture (among the upper class) in Korea during the Goryeo period.
Apart from celadon wares that were produced for the higher social stratum, unglazed stoneware vessels, like the object with the number 29 that had been produced in a similar fashion in earlier periods, continued to be supplied throughout the Goryeo period. Furthermore, Goryeo potters also produced ceramics with black or brown iron glazes (No. 26) which followed similar ceramics produced in Song dynasty China (960–1279).