DIY kioke

If you walk around inside a sake brewery today, chances are you’ll be surrounded by enamel-coated or stainless steel tanks of various sizes, the preferred containers for producing sake since they became widely available after WWII. 

Before then, most brewing tools–including tanks–were made from wood, but due to the popularity of metal (which is easier to clean and maintain) demand for wooden tools and containers dropped to dangerously low levels until the last major manufacturer, Fujii Seiokesho in Osaka, announced that they would close down as their current craftsmen retired.

Kamotsuru in Saijō, the compact sake brewing district of Higashi-Hiroshima, still used wooden koshiki steamers and realised that they would be unable to repair or replace them without Fujii Seiokesho–or rather, without their woodworking skills. So in 2018 the Kamotsuru tōji, Nakasuka, took the bold step of asking Fujii Seiokesho to teach him what he needed to know.

Working with a group of young kurabito, Nakasuka-tōji not only repaired his brewery’s own wooden koshiki but also wooden tanks belonging to their neighbour, Saijōtsuru. And in 2022 Kamotsuru decided to take on the challenge of building wooden kioke tanks themselves, staying at the cooperage while they trained to plane wood and weave the taga bamboo rounds used to hold the planks together. 

So the obvious next step was to brew sake in their new handmade kioke… except the brewery had virtually no experience of brewing in wooden tanks. 

The tōji and kuramoto at Kamotsuru Shuzo in Higashi-Hiroshima assembling a wooden kioke vat. (Taken from the Kamotsuru site)

So Nakasuka started off small, first building a miniature tank for the shubo or starter and using it for small-scale test brewing.

Yeast and other microbes naturally present in the wood contribute to the complexity and depth of sake brewed in kioke, so the kimoto starter method – which also makes use of ambient microorganisms – seemed the perfect choice for creating a balanced sake. 

After the laborious work of grinding the starter materials in half-barrels, they were gathered into one tank and gently warmed over a period of nearly two weeks to encourage fermentation. And the brewery team were rewarded by the appearance of fine bubbles and the delicate sounds of healthy fermentation.

And the ambient yeast remained highly active after the three-stage build for the moromi was completed, producing larger bubbles and almost overflowing from the tank. 

Finally, almost 50 days after starting to make the shubo, the kioke kimoto was ready to press, yielding a beautiful bluish-yellow sake known as aosae (青冴え). It was still bursting with fruity aromas after pasteurisation, but the brewery decided to mature it until it lost some of its younger characteristics, mellowed and developed a longer aftertaste. After a few months, the sake was still relatively clean and crisp but had developed strong umami, which remained among mellower notes when the sake was heated. 

The resulting junmai genshu was deemed good enough to release, and is available from Kamotsuru as “ver. 1.0”, signalling their intention to carry on brewing with wooden kioke tanks – and presumably keep making them too!

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Have a look at the Kamotsuru news page linked below for more photos!

The product details also note that as well as showing interesting changes in flavour with changes in temperature, Kamotsuru find that the harsher conditions of the kimoto starter result in a sake that ages more slowly than usual. They mature it at the brewery for 10 months before release, but also state that consumers can age it at home (in suitable conditions) and enjoy it later without any loss of the rich and complex flavour.

Other breweries who jumped in to preserve the skills to make wooden tools, barrels and tanks include Kenbishi and Kiku Masamune in Nada. Kiku Masamune even opened a Tarusake Meister Factory centre in Mikage, one of Nada’s five villages, where a tour I was interpreting for watched barrel staves cut from cedar being planed and assembled. (Scarily impressive.)

According to an article on Nippon.com, there’s also another factor behind Kiku Masamune’s commitment to producing cedar barrels – a legal technicality means that taruzake produced by storing sake in cedar barrels still meets the legal requirements for sake (seishu/nihonshu) but putting cedar chips into the sake makes it a liqueur!

Sources:
杜氏自らが組み立てた木桶で醸した日本酒　木桶生もと 純米酒 原酒 ver.1.0 Kamotsuru site, 4 Feb 2025 (Japanese)
Barrels of Fun: Preserving the Nada Sake Taste and Tradition (Nippon.com, 22 May 2020)