Pottery has been produced in the city of Tokoname, Aichi prefecture, as far back as the 12th century, and since 1976 Tokoname ceramics, or Tokoname-yaki, has been protected as a Traditional Craft of Japan. Tokoname was the site of the largest and oldest of the legendary Rokkoyō (六古窯): the “Six Ancient Kilns” of Japan, and continues to be the leading ceramics production centre in Japan today. Synonymous with Tokoname is the local iron-rich Shudei clay which turns a bright red after baking. Historically this clay was dug up from beneath rice paddies, but nowadays most Tokoname clay is enriched with natural red iron oxide, or Bengara (弁柄), to achieve similar levels of iron. When fired a second time in a reduction oven, the red clays turns black – another characteristic colour of Tokoname-yaki.
Tokoname Kyusu teapots are typically unglazed on the inside, allowing the tannins in the tea to interact with the iron in the clay body, which is said to reduce astringency and highlight the sweetness of green teas. Another key feature are the perfectly fitting lids, which are ground into the body after firing in a technique known as Suriawase. Besides red and black, Tokoname wares also come in a variety of colours and finishes by mixing other pigmented clays or coating in Chara (チャラ) slip glaze, as well as traditional decorative techniques such as Yōhen (窯変) ombré and Mogake (藻掛け) "seaweed covering".