Cast iron, not bronze — and the water it boils is not the same water.
Everything else in this room is bronze poured at Takaoka. This is iron, and it is from the other end of the country: Morioka, in the far north, where the Nambu lords brought in a kettle-maker from Kyoto in 1659 and told him to stay.
The pattern of small raised dots covering the body is arare — hail. It is not decoration applied afterwards; each dot is punched by hand into the inside face of the sand mould, hundreds of them, before a drop of iron is poured. A good kettle has them in even concentric rows that hold their spacing all the way round the curve of the belly, and that is the first thing anyone who knows picks it up to check.
The shape is cut in wood, then taken in sand.
The arare hobnails are punched into the inside face of the mould, one at a time, hundreds to a kettle.
Iron is poured at about 1400°C.
Fired over charcoal so the inside oxidises black and will not rust.
Lacquer and iron-tannin brushed on while the metal is still hot.
The reason people buy one is what it does to water. Bare cast iron gives up a little iron into the water as it boils, and Japanese tea people have said for centuries that it rounds the water and makes tea taste softer. What is not folklore: the iron is real, in a form the body can use, which is why iron kettles come up in conversations about anaemia in Japan more often than you would expect.
The rule that follows from that is absolute. Never wash the inside. Never use soap, never scrub. Boil, pour out, and leave it on the residual heat until it is dry inside — a kettle left standing wet rusts, and a kettle scrubbed clean has had the film taken off it that made the water taste right.
A tetsubin is not a teapot. It has no strainer and you do not put leaves in it; it boils water, and the water goes into a separate pot. The lookalike with an enamel lining is a kyūsu for brewing, and it will do nothing at all to your water.
The far north, and the only place in this house that works in iron. In 1659 the Nambu lords brought a kettle-maker up from Kyoto and kept him; the domain had the iron sand, the charcoal and the clay for moulds within a day's walk, which is the whole reason the trade took here and not somewhere warmer.
Pieces are found one at a time, in Japan, and photographed before they are listed. Tell us what you are looking for, and we will write when something arrives that answers it.
We write when there is something to write about — some months twice, some months not at all.
Noted. We will write when something arrives.