Tetsubin are traditional cast iron teapots. The craft of cast iron, known as nambu-tekki , has been in practice in the northern prefecture of Iwate for over 400 years. There are 64 to 68 steps in the traditional production process of cast iron. Many of these steps are still done by hand and are strictly monitored by a master craftsman known as a kamashi . A minimum of 15 years is required to become a nambu-tekki craftsman, and 30-40 years to become a kamashi.