https://news.ycombinator.com/item?id=19253616

https://www.setouchiexplorer.com/soy-sauce-wooden-barrel-making-on-shodoshima/

More than soy

For the past 150 years, the Yamamotos and their millions of microbes have been making the family’s Yamaroku soy sauce by mixing soybeans with wheat, salt and water, and letting it ferment in a four-year process. But as more and more of Japan’s soy brewers have swapped their wooden barrels for steel tanks, a big problem has occurred: the country is running out of kioke, and almost no-one knows how to build them. In the last seven years, Yamamoto has set out to learn this ancient craft and teach it to others to try to ensure its survival.