In practical terms, mizunara (Japanese oak) is a nightmare to deal with for whisky makers. It's very difficult to get hold of, expensive to source and a pain for coopers to work with. In spite of all this, whisky makers in Japan - and, indeed, some abroad - are enamoured with it. The aromas and flavours developed during the maturation process (think incense, Japanese temples, sandalwood and truckloads of coconut) are so beguiling, they're willing to put in the blood, sweat and tears.
Chichibu Distillery founder and master distiller Ichiro Akuto remembers his first encounter with mizunara very well, "It was around 2004 at Bar Whisky-S in Hibiya, Tokyo. They served a 40 Years Old Yamazaki that had been fully matured in mizunara. It was wonderful beyond description. I fell in love with mizunara there and then. It was such an impressive and unforgettable experience." Shortly after, he found himself sitting on 400 odd casks from Hanyu Distillery, rescued in the process of transferring the Akuto family's liquor business to a new owner with zero interest in the whisky side of the operation. Ichiro's first work with mizunara dates from this time. "After I set up my own company, Venture Whisky, I transferred some of the Hanyu stock into mizunara casks I had purchased from a couple of independent cooperages."
When Ichiro set up his own distillery, Chichibu, in 2007, he continued his love affair with mizunara. He had his washbacks - six initially, now eight - made out of mizunara, a first in the world of whisky, and started filling new make into mizunara casks whenever he could, which was not very often. It wasn't easy to get hold of mizunara casks. Maruesu Cooperage in the village of Hanyu was one option, but the owner and master cooper, Mitsuo Saito, was getting on in age and keen to retire. Nikka Cooperage, still independently run at the time, was another. In April 2010, the Nikka Cooperage became part of The Nikka Whisky Distilling Co, which meant they could no longer supply 'rival' whisky makers with casks. Ichiro knew it was time to go straight to the source, that is to say, to Asahikawa in Hokkaido, home to the largest hardwood log auction in Japan, and take matters into his own hands… literally!
"I went to Hokkaido to purchase mizunara wood for the first time in 2010," Ichiro says. "I went just once, that year, but after that, we started to go regularly. The mizunara logs are sold in the wintertime, between December and March. Since 2011, we've been going four times a year, on average." The logs are sold by blind auction. Each session consists of three days, two days to inspect the logs and one day for bidding. With around 5,000 logs to be sold on that one day, "It's not like Sotheby's," Ichiro explains. "People interested in a log submit their bid blind and the highest bidder wins. It all happens very quickly. Within 15 seconds of a log being called, the winner is announced. Based on that information, we can modify our bid for the next log we're interested in. Obviously, in the course of the day, prices tend to go up. Sometimes we get lucky, especially when a certain big whisky producer starting with S isn't around. Then, we can buy the wood we want very easily."
The mizunara auction is competitive. Whisky producers aren't the only ones interested in purchasing wood, but compared with high-end furniture makers and the like, they can't afford to compromise. They need the best and therefore most expensive wood. When Ichiro inspects the logs, he's looking for a number of things, "Of course, we have to avoid wood with defects, but it also has to be as straight as possible, have the proper diameter (ie. between 40 and 60cm) and be tight-grained."
Buying wood is one thing, making casks is another. Initially, Ichiro had his logs cut into staves in Hokkaido, where they were then air dried for about three years. Where these staves were going to be made into casks was still up in the air at the time. However, in the summer of 2013, it became clear that Ichiro would be able to take control of the tree-to-cask process. At the age of 86, Mitsuo Saito felt it was time to hang up his hat. Ichiro purchased all the equipment from the master cooper and set up a cooperage at Chichibu Distillery, a bold move for such a small-scale operation. It wasn't until October 2016, however, that the first mizunara cask entirely made in-house was completed.
The wood for cask #6818 had been bought in early 2011. Half a year later, the logs had been cut into staves in Hokkaido and left to air dry for two years. Then, the staves had been moved to Chichibu, where they were patiently waiting to be put to good use. The two young coopers at the distillery, Masashi Watanabe and Kenta Nagae, started their 100 per cent in-house mizunara cask project (they had fitted some casks with mizunara heads before) by making two mizunara hogsheads. Mizunara has fewer tyloses - the balloon-like swellings that fill the vertical-running vessels of a tree - than American or European oak, and is much harder to use for watertight cooperage. When the coopers at Chichibu Distillery tested their first two casks, both turned out to leak all over the place. Rather than have two leakers, they moved staves around until they had one good cask - the 'survivor', as they affectionately call it.
Clearly, this wasn't going to be workable long-term; making two casks and ending up with one good one at best. Some coopers in Japan tackle the leaking-issue by painting the outside of their mizunara casks with kakishibu (the fermented tannin juice of unripe, astringent persimmons), which was traditionally used to waterproof umbrellas, wrapping paper and so on. Ichiro is skeptical about this 'solution'. "It may be completely natural, but casks need to be able to breathe so just painting the outside to stop them from leaking may solve one problem but create another. To me, it sounds a bit like painting the outside of a cask with paraffin or something like that." Never one to cut corners, Ichiro was keen to work out a structural solution.
The problem with the staves used during the first attempts at making mizunara casks in-house was that they had been sawn rather than split. With wood rich in tyloses - eg. American white oak - this is not a problem, as it can be sawn in a number of planes and still be impermeable, but more porous wood like mizunara demands to be split in specific planes, following the vessels running through the wood if it is to be watertight. When we are at Chichibu, half of last season's logs are lying side by side outside the cooperage. "Very straight wood can be cut by saw and left up in Hokkaido," Ichiro explains, "but as you can see, this isn't the best wood. Most of it is a little bit twisted, so if you saw these logs into staves, you cut through the vessels in the wood and the casks will leak. However, if we split these logs by axe, we can make watertight casks out of them. So we bring the logs to Chichibu and take care of that here. For hogsheads, we need staves that are about 1m long, so we can take 1m portions that are relatively straight out of these 'imperfect' logs."
With just two coopers to take care of all the work, splitting logs manually would be a bit wearying. Ichiro and his staff came up with the idea of attaching an axe to one of the hoop-press machines at the cooperage and have since been using that to split logs into staves. "Once we started using those staves, we had no leaks on the outside whatsoever. We just observed some small leaks on the chime of certain staves, but those are easy to fix. We just put a small wooden nail in the wood and the leaking stops. We're making progress," Ichiro says with a smile.
So far, 10 mizunara casks have been made at Chichibu cooperage. Asked how long it takes to make a mizunara cask now, Ichiro says, "Not so long, maybe one week from rough staves to cask. If we had more people here, we could make 10 casks a day, but we only have two coopers and they have many other things to do as well." Most of the mizunara casks made at Chichibu Distillery are hogsheads. The cask being raised when we're there is an exception, a puncheon. "There is an independent cooperage in Japan where we can buy mizunara puncheons if we need to," Ichiro clarifies, "but if we want mizunara hogsheads, well, we have to do it ourselves, so that's why we are focusing on that." Hogsheads are a bit harder to make, because mizunara staves are slightly thicker than normal (38mm) and hogsheads staves are by definition shorter than puncheon staves, so they can crack more easily when bent into shape.
Asked whether he has any idea of the cost involved in making one mizunara cask in-house compared with the cost of using an ex-Bourbon cask, Ichiro shrugs and says, "It's difficult to calculate, but it's much, much more expensive. At the moment, I don't want to calculate the cost. So far, we've only made a handful of casks, so the cost is very high. In the future, once we are constantly making mizunara casks, I may have a stab at checking the cost. Then again, I may not, because I'm afraid I would give up if I knew exactly how expensive they were."
Walking around the cooperage, it's clear that traceability is important. All logs and staves are marked with a number, and he tries to make casks from one or a very limited number of logs as much as possible. "It's still early days, of course," Ichiro says, "but using these numbers, we can trace the wood back to the place where it grew and the part of the tree it came from."
One of Ichiro's dream projects is to make casks from locally sourced mizunara. "You can find mizunara trees in forests in Chichibu above 1,000m altitude," he points out. "We're not allowed to cut down trees in the national parks, but it is possible to purchase mizunara wood from privately-owned forests in the mountains around here. We've explored some of the forests here and identified trees that could be used to make casks."
Consider this - in 2010, the staff at Chichibu planted some mizunara trees near the distillery entrance. Looking through the window, we jokingly remark they could come in handy in 150 years. "Please be patient," Ichiro says with a smile… But we get the distinct feeling he's only half-joking.