Tetsubin (unlined iron kettle)
An unlined cast iron kettle for boiling water over a heat source. It is not a teapot and leaf never goes in it. The interior is bare iron, and it is that bare interior — not the shape, not the weight — that separates a tetsubin from the enamel-lined pot it is usually sold beside.
Identity
- Category
- Kettle
- Native name
- 鉄瓶
- Romanised
- tetsubin
- Also called
- iron water kettle, unlined cast iron kettle
- Material
- Cast iron, unlined, sometimes with a lacquered exterior
- Typical capacity
- 700–1800 ml
- Skill level
- Advanced
Porosity
Not porous. It contributes nothing of its own to the liquor, so it can be moved between teas freely and washed with detergent without consequence.
Not porous, but not inert either. Bare iron builds a mineral and oxide layer in use, and water boiled in a well-used kettle is commonly described as tasting rounder. TeaHQ has not found a controlled comparison establishing how large that effect is, and the claim is repeated far more confidently than the evidence for it warrants.
Where it comes from
Japanese, with named regional traditions including Nambu ironware from Iwate. The form long predates the exported lined teapot.
Named here rather than presented as generic equipment. The object belongs to a practice, and TeaHQ describes it from the outside.
If you do not own one
Any kettle boils water to the same temperature. This is a slow, heavy and demanding object bought for the ritual of it and for heat that stays put, not for a measurable improvement in extraction.
This one is not marked essential. The tea can be made without it.
Brewing methods it is used for
- Gongfu brewing (gaiwan) — A high-leaf, low-volume, many-infusions approach: a great deal of leaf in a small vessel, steeped for seconds at a time and poured off completely, repeatedly.
- Gongfu brewing (Yixing pot) — The same short-steep, high-leaf approach as gaiwan gongfu, carried out in a small unglazed clay pot that seasons over time and is dedicated to one tea.
- Boiling aged and dark tea (zhu cha) — Compressed or aged dark tea put into a kettle of water and brought to a simmer rather than steeped. It is a normal winter preparation for Liu Bao, aged shou pu-erh, brick tea and tea nuggets, and it is also what a gongfu session’s exhausted leaf is for.
Care and maintenance
Empty it after every use and dry it with residual heat rather than a cloth — the inside must not be left wet or it rusts. Never scrub the interior, which removes the layer that keeps it stable, and never put it in a dishwasher.
Other kettles
Sources
This page is TeaHQ synthesis. No external source stands behind the description, the material or the account of how the object is cared for. Where the record names a tradition, that attribution is TeaHQ’s own reading of common practice rather than a citation.
TeaHQ names no maker, brand or shop and has nothing to sell. Nothing on this page should be read as advice to buy the object — the substitute note above exists because owning it is usually optional.
Written comparisons
Where TeaHQ has set this piece of teaware against something it is routinely confused with, and argued the differences out in full.
- Tetsubin vs enamel-lined iron teapot — The most consequential teaware confusion in the export market, because getting it wrong destroys the object. A tetsubin is an unlined iron kettle for boiling water; the lined pot sold alongside it is a teapot that must never go on a heat source.