Cast iron teapots have been in use in Japan since the 17th century. There are two kinds of cast iron teapots: the kyusu used for brewing tea and the tetsubin used for boiling water and transferring it during the tea ceremony. The Tea Route imports teapots from China. The teapots are decorated on the outside with a variety of relief patterns, while the inside is always enamel-coated. The major advantage of using a cast iron teapot is that it will keep your tea hot.