Red ocher is a black red clay containing a large amount of red iron oxide, which appears among the stones in which limestone or shale is decomposed, and is used as a premium pigment. It is also called Cheolsa, Cheolju, Hyeolsa, Jato, Daeja, Juto, Toju and Daehyeokseoktoju.
When this iron oxide soil is applied as a pigment and is fired on the white clay soil, the rust will look iron or copper in color. Such porcelain is called Red ocher porcelains (Seokganju). The red ocher is made of black red soil containing a large amount of iron, and it is used as a coloring pigment. It is also called the earthenwares glazed by using dust, leaf compost, and red ocher as a melting agent.
If you look at the record of Yeongjosilrok, “I used red ocher when painting on porcelains in the old days, but now use navy colors, which is too luxury trend. From now on, navy colors are fully prohibited from use unless on alcohol jars.” The red ocher here refers to pigments of iron oxides.
On the other hand, red ocher was mainly used as a coloring material to express the flesh color of character paintings and landscape paintings. Red ochers, also used in mono or ceramic materials, can be burned to iron and made from ferric oxide (Fe2O3) or by baking ferric sulphate, that is green algae, and made in a variety of colors, including dark red, yellow-red, and pale red.
Likewise, soil containing natural iron oxide or the colored glazes with iron oxide is called iron-containing glazes. Red ocher glazes, dark red glazes, iron-containing glazes, black glazes, tianmu glazes and iron-irabo glazes are all included here.
During the late Joseon Dynasty, the main types of seogganju ceramics in various parts of the country were living containers such as jars and bottles. The body is made of white clay, but the wall is thick and heavy, and the bottom of the bowl were rough. The quality was not good because the main demand group is ordinary people and they were produced based on quality rather than quality. However, the rough and skillful workmanship is simple yet fresh.
Red ochers generally resemble white porcelain bowls, especially when the bottom heel is like the white porcelain bends produced in the 18th and 20th centuries. As time goes down, the body gets wider and the shape is varied, which is also similar to white porcelains. The biggest feature is the fact that there are a lot of multi-sided jars and a unique modeling sensation that cuts each side.