Celadon Jar with Incised Decoration and Double Rings

This jar was unearthed from the Luoyang region of Henan province. Proto-porcelain, which has a glaze of greenish tinge, appeared during the Shang dynasty. Developing from stoneware with pressed decor, it was a transitional product from pottery to porcelain. During the Western Zhou period, glaze became a necessary component of proto-porcelain. It not only functioned to reduce porosity and make vessels easier to clean, but also served a decorative purpose. Because the glaze includes a proportion of iron oxide, it usually shows a greenish tinge.