How to Take Care of Nanbu Tetsubin (Japanese Cast Iron kettle)

Japanese Tetsubin or Japanese Cast Iron Kettle is a great cooking utensil used for making excellent tea. Taking care of a cast iron kettle is a quite difficult task, so we decided to help you in this regard. Below we have provided a short guide that will assist you in taking care of your kettle. 

• Right after boiling the water in tetsubin, pour out the excess water and remove the lid to evaporate the remaining water molecules. Never heat the cast iron kettle without water inside. It will cause some serious damage to your kettle. The black point (Urushi sealing point) will be peeled off, leading to leakage of water and cracks. 
• Never add cool water to the heated tetsubin. Whenever you replenish freshwater to the cast-iron kettle, leave a certain amount of hot water inside the tetsubin. If cool water is added to the empty heated tetsubin, it will damage the kettle and cause sudden shrinkage of the material. If tetsubin already contains some hot water, the temperature on the surface of the kettle will remain stable and never go higher than 100 Degree Celsius. The temperature will go higher and higher if the tetsubin has no water while heated, which can sometimes cause cracks.
• After using the cast-iron kettle for a few days to a week, you will observe some red spots on the surface of the tetsubin. This is normal because when used, these spots appear on the bottom of every new tetsubin. These spots appeared due to the reaction of minor minerals that remain on the surface of the kettle. Always make sure not to touch, wash, or scrub these spots; they will get vanished by themselves.
• You will observe some white spots on the bottom surface of the tetsubin after using it for about 2 weeks. You don’t need to worry about them because these are also normal. Some natural minerals such as calcium carbonates form this layer of white spots. Don't try to remove this layer, as it will save your kettle from rusting and plays an important role in improving water taste. The old tetsubins, if kept in good condition, always have a thick layer of white scale.
• Never use a sponge, brush, oil, soap, or detergent to wash or rub the interior or exterior part of the cast iron kettle.
• Don't leave any water inside the Japanese cast iron kettle for a long period. If you leave the water inside the kettle for more than a day, it will get rusted; if your tetsubin gets rusted accidentally, never use physical strength or any detergent to remove it. Put green tea leaves or green oolong tea leaves inside the tetsubin and boil them with water. Switch off the heat and let the water cool down naturally. Leave it for a few hours, and these antioxidant leaves will react with iron to turn black and hide the rust. If the exterior part of your tetsubin gets rusted, heat the kettle and then apply tea leaves to its surface. 
• To maintain the glossy outlook of your cast iron kettle, you can use a piece of cloth soaked with tea to polish the surface of the tetsubin.