Tetsubin
Hinomaru

This Tetsubin is cast in a sand mould that is elaborately decorated with stamped or freehand motifs before it is fired in charcoal at 800°C to 1000°C to form a solid mould into which 1500°C molten iron can then be poured. Once the iron has cooled a little, the Tetsubin is removed from the mould and is checked for even thickness by tapping with a hammer. To prevent rust from developing, the Tetsubin is covered with lacquer and baked in charcoal again, this time at 900°C, to create an oxide film inside the kettle in a process known as Kamayaki (釜焼き "iron pot firing") which is unique to Nanbu Tekki cast ironware. In the final step, the Tetsubin is coated in Ohaguro (おはぐろ): a rust-preventing liquid made by putting pieces of steel in acetic acid and brewed tea, which also adds colour to the surface.

Before use, season the Tetsubin first: Pour hard water (preferably with a hardness of about 300mg/l, such as Evian or Vittel) into the Tetsubin so that it is about 80% full, to prevent spillage when boiling. With the lid off, heat the Tetsubin over a medium heat on a gas or electric hob, or low to medium on an induction hob, for about 20 minutes. Then place the lid on, take a kitchen towel or oven mitt to grab hold of the handle, and carefully discard the boiling water. Remove the lid and leave to dry with the residual heat on top of a trivet or protected surface – never put empty Tetsubin on a hot hob. When the Tetsubin body has cooled down, repeat this process two more times. As the calcium and magnesium in the hard water crystallise when boiled, this creates a protective layer of scale inside the Tetsubin to stop rust developing. Once the Tetsubin is seasoned, boil water using the same procedure, ensuring to take the Tetsubin off the heat as soon as it has boiled to prevent overheating and pouring all the water out while it is still hot.

Never leave water, hot or cold, standing in the kettle. Do not put it in the microwave, oven, dishwasher or dryer. Do not boil or brew tea in a Tetsubin, only plain water. Fill between 50% to 80% and always boil with the lid off or tilted to prevent water from boiling over. Always leave to dry with the lid off. Do not clean the inside of the Tetsubin, so that the scale/patina remains intact. Clean the outside with a dry cloth and wipe off any moisture straight away. It is recommended to use Tetsubin often, and when not in use please store in a well-ventilated place. Although highly durable, please do not drop the Tetsubin as this can lead to fractures.