Goishicha (碁石茶, go stone tea) is a rare Japanese dark (post-fermented) tea made in Ōtoyo Town, Kochi prefecture.

It’s classified as a type of bancha, although it’s not a green tea.

The reason it is called goishicha is that it resembles the black stones of the board game “go“.

This tea goes through two fermentation steps, one by mold and the other one by lactic acid bacteria.

In the second fermentation process, the tea is pickled. That’s why it has its distinctive sour taste.

Although it was mostly used as an ingredient in chagayu (a Japanese rice porridge with tea), nowadays people have begun to drink it as any other tea.

Because of declining population in the area and demand in general, goishicha production was about to be stopped and eventually disappear.

Luckily, and thanks to local government support plus a trend for healthy teas, it is now available again.

Processing of goishicha

Steaming: The branches with tea leaves are steamed in a barrel. Juices of the tea leaves are collected for later use.

The branches with tea leaves are steamed in a barrel. Juices of the tea leaves are collected for later use. Fermenting: Tea leaves are stacked in a room and are covered. Fermentation takes place with the help of mold.

Tea leaves are stacked in a room and are covered. Fermentation takes place with the help of mold. Pickling: In a pickling barrel, the leaves are sprinkled with the juices in the first step and are also compressed. The lactic acid bacteria starts the second fermentation process.

In a pickling barrel, the leaves are sprinkled with the juices in the first step and are also compressed. The lactic acid bacteria starts the second fermentation process. Cutting: Compressed leaves are taken out of the barrel and cut into small blocks.

Compressed leaves are taken out of the barrel and cut into small blocks. Drying: The blocks of goishicha are left outdoors under the sun to dry.

Source: http://www3.synapse.ne.jp/hantoubunka/minzoku/02.22.htm

To see the process, check out this video I found. It’s in Japanese but if you’ve read until now, you’ll know more or less what’s happening.

How to make goishicha

To brew in a teapot, use one block (about 2 grams) of goishicha and pour 350 ml (11.6 oz) of boiling water. Brew for 4 to 5 minutes.

You can make up to 4 infusions.

For larger amounts, use a liter of water and add one or two blocks of tea and brew 4 or 5 minutes over medium heat.

Finally, I’ve reviewed a goishicha from Furyu in the next post, just in case that you are curious about its taste.