I normally use a Japanese cast-iron kettle every morning for tea. Drinking water containing a moderate quantity of rust is good for our health. A bit of iron improves the taste of the water, making it more mellow and sweet.
Cast iron kettles, known as tetsubin in Japanese, have been in use for at least five centuries. They are hand crafted, beautiful objects, showing a ‘Spartan’ simplicity, which are used to heat water to be then poured into a temmoku bowl for the tea ceremony or, as I am doing, into an ordinary porcelain teapot.
The inside part of the tetsubin is either plain or covered with a black layer of urushi a plant belonging to the same family of the Mango tree which is traditionally used to produce a coating material.
The period of civil wars in Japan ended in 1603, when Tokugawa won the Sekigahara battle, uniting and stabilising the Country. A lot of sword-smiths found themselves without orders but the steady demand for home implements persuaded them to transform themselves into producers of kitchen knifes and tetsubin.
In the region known as Tohoku the local king, Nanbu Toshinao, was a great fan of tea drinking and called several masters – in particular the Suzuki, Koizumi, Arisaka and Fujita clans – to work for him, so much so that, even today, that region remains the centre for tetsubin production. Some of them still bear the names of those artists, produced by their descendants. While their antique pieces call for very high prices among tea enthusiasts and art collectors.
The best pieces of tetsubin are still produced with clay mould following the original methods where, for the top-end models, the mould is used only once, for low end it is recycled up to 100 times.
Once the clay mould has been prepared and before baking, the external design which will appear on the tetsubin surface, is impressed. Traditionally there are three main patterns: the Arare with small knobs on the surface; the Hada, with a skin surface; finally the picturesque type, with flowers, horses, cranes.
The spout is moulded separately and then attached to the body; the lid is also produced later, with the right dimension and the right knob.
The advantage of using cast iron (1,7 to 4.5% C and 1 to 3% Si) instead of common iron is that cast iron is more fluid, having a lower melting point and shrink less while cooling. If the shrinkage is too high the kettle may crack.
After the casting the kettle is baked in charcoal fire, which takes away oxygen from its surface, giving to the vessel a blue-grey colour. This is a very important process for the inside part where it will come into contact with water.
The final stage is the application of the handle, which is made through forging, not casting. It is in some cases hollow, for some high-end products, with small holes to disperse the heat and for some medium to low level it is made solid.
There is a particular kinds of tetsubin which are produced in Kyoto, which have silver inlays inside the handle and the body. They are known as Kyoto-style or Seko-do.
How to see if your tetsubin was hand made or is an industrial product? Simple, look at the inside of the vessel and if you can see two hammered spots at the bottom, known as katamochi – the 2 nails used to fix the internal mould during the casting – it was hand made using a mould.
A newly made tetsubin produced by an anonymous workshop with a capacity of approx.. 1.4 litres of water may cost between 600 to 800 USD. If it is by a master who had signed it, it may cost from 800 USD up to a few thousands.
There are few points to remember for taking care of your tetsubin. After use it the inside should be completely dried, because water may create an excess of rust inside. The second point is that it should be not heated at full fire but gradually, as it may crack.