How to care for a Japanese cast iron teapot

What cast iron teaware do we carry?

We carry Ikenaga's Nambu ironware, cast in Iwate Prefecture, the home of the Nambu tekki craft. Six pieces are on our shelf right now: five kettles built for the stove and one teapot for the table. The three matching 1200 millilitre kettles, Doraemon at $479.20, Haru at $348.60 and Sakura at $348.60, all run on gas, induction and charcoal; their handles do not fold. The Tetu 1000 millilitre kettle at $470.40 was designed by furniture designer Makoto Koizumi with a handle that folds flat, and it is also rated for gas, induction and charcoal. The plain Nambu ironware 1000 millilitre kettle at $348.60 is listed for gas or direct fire only, and its handle does not fold. The Pine and Crane 550 millilitre teapot at $244.00 is the one piece for the table, not the stove: it is for brewing only, filled with water boiled elsewhere rather than heated directly. Its handle folds down too. Every listing describes the pieces as handmade, so small scratches or unevenness are normal rather than a fault.

Enamel-lined teapot or raw tetsubin: which is which?

The two are not interchangeable, and the difference comes down to what lines the inside. A raw, unlined tetsubin is bare cast iron inside and out, and that bare iron is what it is traditionally used to boil water in. Iwate ironworkers bake a raw tetsubin over a charcoal fire at 800 to 1000 degrees Celsius, which fuses a magnetic oxide layer onto the surface and is what keeps the bare iron from rusting straight away. An enamel-lined piece has a coating baked onto the interior instead, which makes it easier to keep clean but also means it cannot go over direct heat, since the heat would crack the enamel. Every Ikenaga teapot and kettle we currently stock is enamel-lined. Some of those enamel-lined pieces are still rated for the stove, gas, induction or charcoal, because the maker built the enamel to handle it; others are teapots only, meant to hold water that was boiled elsewhere and poured in, not to sit over a flame themselves. Check the individual listing before you put any piece on heat, since the two types look similar from the outside.

How do you look after an enamel-lined teapot or kettle?

Wash it by hand, and skip the dishwasher completely. Ikenaga's own listings are consistent on this across the range: hand wash only, no detergent, no sponge and no scrubbing brush. Wiping the iron with a cloth while it is still hot is what brings up its shine, and the maker notes the surface gains character the longer a piece is used, so that dulling is part of how it is meant to look over time rather than a problem. Keep it off the microwave and away from an open flame unless the specific model is rated for direct heat, since body and handle both run hot regardless and a potholder is worth keeping nearby.

What about a raw, unlined tetsubin?

A raw tetsubin needs a different routine, mostly because there is no enamel standing between the iron and rust. A new one is typically seasoned first: rinse it, then boil plain water in it and throw that water out, repeating the cycle a few times before the first real use. After every use the interior needs to be properly dried, and the standard advice is to use the kettle's own residual heat with the lid off rather than just air-drying, since leftover moisture sitting in a cool kettle is exactly what turns into rust overnight. With ordinary use the interior changes on its own: red spots appear first, and then a white film of scale forms, which the maker says not to scrub off. Iwachu puts it plainly: "the water will remain clear even if the inside is red, and the taste of the water will become even more delicious." If the boiled water ever does go cloudy from rust, the fix is to simmer sencha in the kettle for about half an hour, a treatment that works through the chemical reaction between the tea's tannins and the iron. None of our current Ikenaga stock is a raw tetsubin, so none of this changes how to treat what is actually on our shelf; it matters if you already own an older or inherited piece, or if you are buying one elsewhere in the unlined style.