Nanbu-teki: cast Iron that improves the water quality
The most important factor in the Japanese water treatment is the use of Nanbu Teki. This is the cast iron craft from Iwate prefecture, in the north of Japan. In the cities Morioka and Oshu (Mizusama) they have ‘nezumi chutetsu’, a very special quality of iron.
In Japan Nanbu Teki has been used for centuries to boil the water, because this significanty improves the water quality. In Europe, because of the generally hard water quality, this effect is even higher!
By boiling the water in Nanbu Teki kettles, the water becomes more round and tastes softer, with less additional side tastes. This makes it perfect for making tea. Nanbu teki kettles are finished on the inside with naked cast iron (so not enamelled).
By bringing the water in direct contact with the iron, there is an exchange of iron-ions: bad iron-ions attach to the edge of the kettle and make a layer called yu-aka. This layer releases good iron ions to the water.
When buying a new Nanbu-teki kettle, the first weeks you use it to boil water, this layer will start forming.
Binchotan: Japanese charcoal that filters water
Before boiling the water in Nanbu Teki, you can filter it by putting it in a carafe with 2 pieces of Binchotan. Binchotan is charcoal from Japanese oak. This charcoal has a honeycomb structure on the inside, through which water circulates. This reduces the size of the water molecules, which makes the taste of the water softer.
Additionally chlorine and other chemical substances are filtered out of the water. Because Binchotan removes also the chlorine from the water, it is advised to keep it in the fridge, so the water doesn’t get contaminated with bacteria.
If you use Binchotan daily, it is advised maintain it weekly as follows:
- scrub it under cold water with a strong brush
- boil it for 10 minutes.
- cool it down immediately with cold water
- let it dry before putting it back into water
You will notice in the boiling water that this process cleans the Binchotan.