Summary :
The traditional cast iron kettle: the tetsubin. Its history is closely linked between China and Japan.
It originated in the Chinese Tang and Song dynasties as a kettle, it was introduced to Japan in the 1780s through Japanese monks returning from China. Its high quality cast iron obtained by traditional technique, with its texture, its rustic shape, is attributed to Japanese know-how and spread in Japan, at the same time as the fashion for sencha developed at that time. Indeed, in the middle of the 17th century, China introduced Japan to a kind of leaf tea, sencha, which however did not yet have the success that matcha, the powdered version, had. This soon became a fad, especially in wealthy society. This is how the tetsubin has become more and more fashionable. Around 1800 with sencha becoming really popular among the wealthy Japanese, the iron kettle was gradually introduced and revisited in its manufacture and taken up by artists of the time. It was therefore during the 19th century that the simple models of kettles that were the tetsubins, became real, very elaborate masterpieces, however very influenced by Chinese culture (calligraphy, poems and Chinese quotations etc.)
The Japanese cast iron teapot only became popular in the 18It is and 19It is century, increasing until the beginning of the world war when it fell back into oblivion. It was the Taiwanese who first rediscovered the value of collecting old tetsubins.
The authentic tetsubin is made of cast iron without enamel. Some kettles are treated in the Japanese way, that is to say that to activate a natural protection against rust, an oxidative cooking is carried out at 800°C: As cast iron is not porous, the oxidation process does not can propagate to deeper layers and the rust remains on the surface creating a barrier against itself. Or the pot can also be coated with a natural tree lacquer, a vegetable fat that gives the internal wall a black appearance. You can also let the limestone appear after repeated use of the teapot, this cumulative layer is a natural anti-rust.
And then we have the Chinese way, the cast iron teapots are coated with an anti-rust coating that withstands the strong heat source.
A little word all the same on the molding of cast iron, we can retain 3 essential techniques, without dwelling too much on them, the explanations being very technical.
The waxing method, the one that makes a single model, precious, collector's item. The model of the casting is made of beeswax, and will be destroyed after casting and does not require demolding, resulting in a single model.
The sand method, which is a natural gravity casting method, its distinctive feature is that the body of the pot has a horizontal stripping line which is in a circle around the maximum diameter of the teapot. This process is the reference of a craft still present today.
The die-casting method, with a mold made of steel and other metal resistant to high temperatures. A pump is used to inject the high temperature iron. Its particularity is that the stripping line is vertical with a right part and a left part located at the level of the spout. We recognize this process by the smooth interior finish of the pot, while the finish is more rustic in the case of sand casting.
An enamelless kettle, the tetsubin in this case, allows the water to be enriched with iron while boiling. The result is a modified water which gives a softer, even sweeter tea. As a result, each cup of tea, coffee, plant, provides users with an iron supplement, good for health. In terms of water heaters, cast iron remains the appropriate material, it heats up quickly, and retains the heat for a long time and releases it in a coherent and balanced way. However, it is better to avoid letting the water cool in the kettle to prevent the appearance of rust. If there is still unused hot water, why not put it in a thermos, the kettle will be dried and rust free.
The enameled cast iron teapot of modern times.
Today, the tetsubin is above all the kettle used by tea lovers to boil water during the Japanese matcha tea ceremony.
As the European and Western markets grew, in the late 90s a new colorful design appeared, the tetsubin became a popular and sought-after commodity around the world. Little by little, the cast iron teapots were enamelled on the inside to prevent rust. However, we know that the iron released in minute quantities is useful for the taste for water, for tea. The enamel, from this point of view, deprives of the benefits provided by iron. The tetsubin was originally used for green tea, but all teas are fine in a cast iron teapot with or without enamel.
Maintenance: Rust can appear if the teapot is poorly maintained, poorly dried or with standing water. However it can still be used, rust is not toxic, in fact many tea lovers prefer the taste of tea from a rusty teapot, this of course concerns quality cast iron.
The simplest technique: boil water to 2/3, then empty it of water which is loaded with rust. For heavier rust boil green tea, reduce to 20% and repeat 2 or 3 times. Or also cook rice in the tetsubin.