Tsubame city in Niigata Prefecture is known for producing traditional hand-crafted copper-ware called Tsuiki-Doki, which means "hammered" coppe-rware in English.
Tsuiki-doki encompasses a variety of items, including tea equipment, sake equipment, flower vases, and various accessories. Skilled artists carefully shape the copper plates into the desired forms using a hammering technique. Typically, the copper plate is laminated with tin. Currently, the brands introduced by HOJO use a liner made of 99.99% tin. In the past, they did not use such high-grade tin, but concerns about lead content in ordinary tin led the industry to switch to 99.99% tin.
The beautiful surface colors of the copper-ware are achieved through the firing process, influenced by the oxygen level. Depending on the conditions, different colors are produced. The copper teapots are designed with filters that efficiently sift most types of tea leaves, making them ideal for brewing tea.
With this copper teapot, the internal tin liner which made of 99.99% of tin significantly improves the intensity of flavor and the depth of after taste. It gives a very clean taste with smooth and “silky” mouthfeel. After you have drunk the tea, it does not leave your mouth feeling dry or astringent; instead it gives a lingering after taste that is complex and evolving. Thsi materrial does not enhance the body. It keeps body moderate that makes the taste of tea gentle. This teapot is suitable for most types of tea, unless you are a person who may not like to enjoy strong after taste.
The tin liner may get dark spot in a long run. However the performance of tin does not really change or decrease even if the tin is oxidized. Most importantly, after using the tsuiki-doki teapot, we have to leave the lid off and let the teapot dried completely. When the teapot is used for a long time, some layer of scale might be formed on the surface of tin and this will protect the teapot from the rust. It is very important to stick to one type of water for both brewing and washing. I have experienced that the teapot that is used by my friend for a few months, when I used it with my own water, it never perform as how it is supposed to be!