Japanese Cast Iron Teapot vs Tetsubin: Which One to Buy

Buy an enamel-lined cast iron teapot if you want to steep tea at the table, and buy an uncoated tetsubin if you want to boil water on a burner. They look almost identical in a photograph, they are both Nambu ironware from Iwate, and swapping them ruins one of them: heat an enamel-lined teapot dry and the lining peels, brew tea inside an uncoated kettle and you leave liquid sitting on bare iron.

The specifications, care wording, and heat-source ratings below come from Iwachu's and Oigen's own pages and from the US listings that carry their kettles, checked on September 4, 2026. The photos are Japanese homes using both types; they are examples, not a measure of how common either one is.

Quick answer

• Want to brew tea: get the enamel-lined teapot. It rinses clean and will not rust, but it cannot be heated and holds only 10 to 22 ounces.
• Want to boil water: get the uncoated tetsubin. It lives on the burner, but it needs a break-in boil, a dry-out after every use, and it is heavy for its size.
• Cook on induction: buy only a kettle the maker rates for induction. Iwachu marks those models with an IH notation; the enamel-lined teapots are not among them.
• Want one object that does both: that means an uncoated kettle plus a separate pot for leaves, not a lined teapot pushed onto the stove.

Why the two get mixed up

US listings call both of them "cast iron teapot," and often use the word tetsubin for both. The shapes overlap too: a squat pot with a hailstone pattern and an arched handle can be either one. The difference is inside. Iwachu's teapot line is enamel-coated within, which is why the maker says it will not rust even if moisture is left in it and why it wipes clean. Its kettle line is bare iron, which is why the maker tells you never to touch the inside and never to leave hot water sitting in it.

So the question to ask about any listing is not what it is called. It is whether the inside is coated, and what heat sources the maker lists for that exact model.

How the two types compare

Choose the enamel-lined teapot if you want to brew tea

This is the pot that goes on the table. You boil water somewhere else, pour it in over leaves in the built-in stainless strainer, and pour out. The enamel means the inside will not rust if a little moisture stays behind, and Iwachu's care page asks only that you rinse with cool or lukewarm water, wipe off the moisture, and keep metal scrubbers away from the lining. It is also the smaller of the two: 300 ml is about 10 ounces, and 650 ml is about 22 ounces, or roughly two mugs.

The limits are real. Iwachu states plainly that you cannot boil water in it and that no open flame is allowed, because the enamel peels off if the pot is heated dry. It also cannot go in the microwave, the dishwasher, or a dryer. And it is still cast iron, so a 650 ml pot weighs about 3.3 pounds empty, which is a lot of teapot to lift one-handed.

Choose the tetsubin if you want to boil water

An uncoated tetsubin replaces your kettle rather than your teapot. The Iwachu kettle listing describes it as a product for boiling water only and tells you not to touch the inside, because the mineral film that builds up there is what protects the bare iron. Oigen's instructions are the same in spirit: fill to about 80 percent, and dry the kettle after use rather than washing it out.

In exchange you get a pot that can sit on the burner all morning and pour into anything. It is the type in the photos here where the kettle is sitting on a gas burner or on an induction ring. What you do not get is a strainer or a lid you can steep under.

Check the heat source before you buy, not the category

Iron does not automatically mean induction-ready. Iwachu's FAQ says the kettles that can be used on induction carry an IH notation, and names the shapes it calls 7-type Arare and 18-type flat-round Arare; the rest of the kettle line is not covered by that. Oigen sells induction-rated kettles and adds a caution that an induction hob heats harder than a gas flame, so you should start at moderate heat and raise it gradually. One Oigen listing goes further and names gas, an electric heater, induction at 100 or 200 volts, a tabletop induction plate, and a radiant heater, with a warning that long or fast induction heating can deform the base.

The practical rule for a US kitchen: find the heat sources printed for the exact model number you are buying, and treat anything not listed as not allowed. That includes electric coil and glass radiant tops, which some models list and others do not.

Breaking in a tetsubin, and living with rust

A new uncoated kettle is not ready to drink from. Iwachu's instructions are to fill it, bring it to a boil over medium heat, throw the water out, and repeat two or three times. After that, the inside changes color: red spots appear first, then a white scale film settles over them. Iwachu says not to scrub it off, and that the rust is not a problem as long as the boiled water does not turn cloudy. Scrubbing removes the oxide film and makes the rust worse.

The daily routine is short. Empty the kettle while it is still hot, take the lid off, and let the residual heat dry the inside. Oigen adds that if moisture is still there, you can put the kettle back on the heat for about thirty seconds. Never leave water in it overnight.

Weight, heat, and the parts nobody mentions

Cast iron is heavy for the water it holds. The Iwachu 0.9 L kettle is 1.8 kg, about 4 pounds, before you add 2 pounds of water. Oigen's 1.2 L is 1.9 kg and the 1.85 L is 2.8 kg, about 6.2 pounds empty. If wrist strain is a concern, the small kettles are the ones to look at, and the 1.85 L size is a two-hand pour when it is full.

The body and the arched handle also get hot on a burner, so keep a cloth or a trivet nearby, and give the kettle a heatproof landing spot on the counter. None of these pots are dishwasher items, so plan on a wipe rather than a wash.

Our picks

Neither Iwachu nor Oigen runs a US store, so these are the models US-facing retailers carried when we checked on September 4, 2026. Confirm the model number and the listed heat sources on the listing you buy, because both makers sell similar-looking pots under both product lines.

Pick #1: Iwachu enamel-lined cast iron teapot, Arare pattern

The straightforward version of the type: enamel inside, stainless mesh strainer included. The sizes US listings carry most often are 300 ml (about 10 oz, roughly 1.8 lb) and 650 ml (about 22 oz, roughly 3.3 lb), and the same line runs to other sizes, including the 0.55 L pot in the photo. Best for loose-leaf tea for one or two people and for anyone who does not want a maintenance routine. Avoid it if you were hoping to heat it: Iwachu allows no open flame and no boiling in this line. Main drawback is that a chip in the enamel is not repairable, so it needs a soft sponge and a stable place to live.

Pick #2: Iwachu Arare tetsubin, 0.9 L, IH compatible

The smallest uncoated kettle worth buying if you cook on induction: 0.9 L (about 30 oz), 1.8 kg (about 4 lb), 6.9 by 5.9 by 6.7 inches with the handle raised, and listed for gas and for induction at 100 or 200 volts. Best for one or two people who want the kettle on the stove and dislike lifting a full 2-liter pot. Avoid it if you fill a French press and two mugs in one go, because 30 ounces disappears fast. Main drawback is the capacity you get for the price, and the fact that 4 pounds of empty kettle is a real weight on a small hob.

Pick #3: Oigen Nambu tetsubin, arare pattern, 1.2 L or 1.85 L

The everyday boiling kettle. The two sizes with a checked US price are the Kangetsu Arare H-159S at 1.2 L (about 40 oz, 1.9 kg) and the H-159 at 1.85 L (about 62 oz, 2.8 kg), both listed for gas and induction with Oigen's advice to start at moderate heat; the kettle in the photo is a Shin-Kikko Arare H-156 from the same range. Best for a household that boils water several times a day and wants one kettle to cover tea, coffee, and instant noodles. Avoid the 1.85 L if you pour one-handed, since it is 6.2 pounds empty. Main drawback is availability: both sizes were out of stock at the retailer we checked on September 4, 2026, and Oigen stock rotates, so you may end up comparing listings rather than picking a size.

Ready to buy?

Decide brewing or boiling first, then check the model's heat sources, then the size. Prices and stock move, so compare the same model number across sellers.

Frequently asked questions