Chouna Shiage – Adze Finishing

One of the more unique tools used in Japanese carpentry is the chouna (adze). As carpentry tools go, adzes are certainly not unique to Japan but the level of refinement and variety of finishes that carpenters in Japan have developed using these tools, is something I’ve never seen anywhere else. I’ve been fascinated with chouna and the finishes they can produce for a long time, but there’s really very little information about how to use them. That does seem to be changing though, with a trickle of information slowing making it’s way to the internet and youtube.

My first chouna was a gift from a retired carpenter who we just happened to meet on our second trip to Japan around 2017. The handle was split and wrapped in some kind of tape to keep the splitting at bay, and it was rusty as can be. After a bit of cleaning and sharpening I got the blade back in shape, but my first attempts at using the tool were pretty crude. You often hear woodworkers and carpenters talking about tools becoming an extension of their body, and I don’t disagree. But more than other tools, I think using a chouna really embodies that statement. When you’re swinging a sharp piece of steel that is wedged onto a bent wood handle, chipping away at wood inches from your feet, you must develop a sense of control and fluidity with the tool. In other words you have to let your intuition be a guide. You can’t start over-thinking things, you just have to start using the tool and adjust you body and swing until you start getting results. At least last been my approach.

I don’t have a ton of advice to offer when it comes to setting up a chouna. I’ve gotten little bits of advice here and there from folks who have been using them longer than me, and I’ve made a couple of modifications to improve performance, but I’d say more than anything I’ve developed a feel for the tool by trying out different chouna, and seeing which handle shape, blade shape, etc. seemed to work best for me. I’m sure with enough time and experience I will develop a deeper understanding and stronger opinions about chouna setup, but for now I’m in the camp of just buy the tool, try it out, and try to develop a feel for it. Better yet, buy two chouna so you can see how they compare in use, and start to develop a sense for what works for you.

I did a little bit of chouna shiage when I was back in the US, but it was working with Somakosha that really opened up some unique opportunities to put the tool to use. One of the first was the watchtower project, which took place early on in my time in Japan. I remember the start of that project beginning like many others, with the boss telling me “Hey Jon tomorrow we’re going to Lake Biwa to build a watchtower… oh and we’ll probably be hewing the whole time so you may want to practice a bit.” So the next day, with one evening’s worth of practice under my belt, we all drove to Lake Biwa, and the 4 of us each took one log to hew. It took most of a day to hew the entire surface of each log. With very little prior experience, being thrown into a situation like that was a good way to get comfortable using the adze. By the end of day 1 we all had blisters, my skinny little forearms became popeye-like, and my hands had no grip strength left; unable to grip or hold onto anything that wasn’t shaped like an adze handle. But honestly it was a really great and memorable experience.

While the watchtower project was a short but intense dive into how to use a chouna, it also gave me the opportunity to try out a variety of other chouna as well, since the carpenters I was with all had multiple, and they were willing to let me try out theirs. Over the past few years here in Japan I’ve also picked up a few chouna at flea markets and junk shops, but the one I like best is my first… the one given to me by the old retired carpenter. Despite it’s somewhat crude appearance I really like how the blade cuts and the overall shape of the handle. It’s great for fine finishing cuts.

All of my chouna are straight edge chouna, meaning their edges are designed for making flat cuts. The finishes you can achieve with straight edge chouna look like what you see in the images above; a series of repeating scallops, creating a wavy texture over the surface.

The other style of chouna are those with round edges, and there are two main varieties that I’m aware of. The first is the hamaguri type, which is more like a carving gouge, with the whole body of the blade being curved. The other is the naguri style, which has a flat body like a chisel or plane blade, but the edge is shaped into a curve. I don’t have much experience with the former, though they have been common at tool shops in Japan, and I’m not sure why. None of the carpenters I’ve met in Japan ever use the hamaguri style. My understanding is that the geometry of a hamaguri style blade requires a series of shallow chops to make a complete scoop out of the wood, whereas the naguri style’s geometry allows the blade to take out a large scoop of wood in one fluid stroke. It’s the naguri style chouna that can be used for the popular “turtle back” finish, which looks like a series of alternating round scoops.

Here’s a video I took of Jon S. from Somakosha wielding a naguri style chouna a few years back. (For lots more amazing videos of this tool in action I suggest checking out @kyonaguri.jpn on instagram. He’s a carpenter that specializes only in chouna shiage, amazing!)

Here is the turtle back finish on a massive beam on one of the gates at Odawara Castle.

This display at the Takenaka Carpentry Tools Museum also shows the turtle back pattern on the right.

Another approach using the naguri style chouna is what Jon S. often did, creating a looser pattern of scoops. Here is some of his handiwork on some beautiful hinoki beams.

And here’s some of my work from the Lake Biwa watchtower project, in a similar style.

These are all beautiful finishes, and something that I’d love to work on more, but at the moment all of my chouna are of the straight edge variety, so I’ve been working on developing my skills with the straight edge style, which creates a finer series of wide choppy scallops. I love this texture and it’s chiseled organic look, and it’s that type of finish that I’ve been experimenting with on a few furniture projects lately, with the most recent being a some keyaki tea trays.

Which brings me to using chouna on furniture. These tools are mainly considered carpentry tools, but there’s really no reason they can’t be used on furniture, and I’ve been having a lot of fun experimenting in that vein over the past few years. How and where to use chouna finishes on furniture can be an interesting design challenge. The turtle back pattern looks great on larger pieces of furniture like tables or even cabinet doors. But for smaller pieces I think the chiseled patterns from a straight chouna look best.

The bottom line is that chouna are fun tools! And I hope more people start using them. They can be intimidating tools in the beginning, but like any hand tool it just takes practice.