Ru ware (Ru kiln celadon) is one of the five great kilns of China’s Song dynasty, renowned worldwide for its elegant, distinctive glaze and exceptional craftsmanship. Its main characteristics are as follows:

1. Distinctive glaze color: Ru ware is best known for its sky-blue glaze, with a smooth, lustrous surface and a warm, gentle hue. The ancients praised its color: “Like the sky after rain, when clouds part and the heavens turn blue.” Its glaze ranges from sky blue to moon white, with variations including bean green and pale green.

2. Glaze surface characteristics: Ru ware glaze often features fine crackle patterns (ice-crackle), evenly and delicately formed, lending it an elegant, refined appearance.

3. Fine clay body: The body of Ru ware is dense and sturdy, usually gray or light gray. After meticulous processing and firing, it is exceptionally durable.

4. Simple forms: Ru ware pieces have clean, balanced shapes and flowing lines. Many are functional forms such as bowls, plates, vases, and cups, though highly decorative art pieces were also made.

5. Thick glaze layer: The glaze on Ru ware is relatively thick and even. Tiny brown specks, known as “sesame-seed flecks,” can sometimes be seen beneath the glaze and are one of Ru ware’s characteristic features.

6. Difficult firing process: Ru ware requires complex firing techniques and precise control of temperature and timing. The low yield makes it extremely valuable.

These characteristics give Ru ware an important place in the history of ceramics, and it is regarded as one of the representative ceramic traditions of the Song dynasty.