Shou Sugi Ban: How to Preserve Wood Using Fire
Modern building practices often use designs and materials which cause destruction or detriment to the surrounding ecosystem and utilize resources which may be cheap to buy but are expensive to the Earth (see for example 1).
Luckily for the Earth, a myriad of projects out there are following the “use and value renewable resources and services” principle with building materials and techniques.
One common natural resource to use is wood, which is renewable in that you can plant more trees, or (even more energy efficiently) if the wood is recycled. But can we build with wood in a natural way that also means the construction will last?
…The short answer is ‘yes’, though some of the methods used may be surprising. One of the things you probably wish to protect your wooden construction from is the destructive power of fire. However, fire can also be used, perhaps paradoxically, to protect the wood.
Last week I learned a technique which involves charring the wood for the exterior of your building from Kentucky-born Mikale De Graff, who says that some traditional buildings in his birthland in the USA use a similar style. De Graff, however, who I work with in Pak Chong, Thailand, has been living in Asia for the past few years and what he showed me is adapted from the Japanase traditional Shou Sugi Ban (焼杉板), literally “burnt cedar wood”, from “Yakusugi” which means “cedar” (2).
The benefits: fire as evolutionary progression
We are fascinated by fire and indeed it can be seen as a universal desire as part of our human condition to make fires (3). Many people speak of the benefits of being around flames, and indeed there have even been scientific studies in the past few years showing that fire helped us to evolve our consciousness as human beings, as staring at flames helps to induce a meditative state which encourages imagination and “multi-step thinking” (4).
In our modern world, however, much of our fire has become relegated to the slightly less mesmerising realms of the sparks which send clouds of black smoke pouring out of our cars and machinery, or the tiny flames of electrical impulse which are shooting through your computer and helping you to see with the lightbulb over your head.
It can be seen as more important now than ever to honour our fiery heritage as this may help us to more easily understand what we have created in our current human society (see for example 5).
On a practical level, playing with fire can also be really fun, and so even if you don’t believe that Shou Sugi Ban will help your consciousness to evolve or for you to be more mindful of how we can achieve positive change in society, you do get to set fire to things in a safe, controlled and beneficial way so there is a clear enjoyment advantage.
More benefits: How effective is it?
In Japan, Shou Sugi Ban has been used for centuries, traditionally (as the name suggests) with cedar wood, though this type of wood has its own history of problems in the country, in terms of the creation of economically-viable monoculture cedar forests after World War 2 which led to the disruption or destruction of many ecosystems (6).
Nevertheless, if you were to visit Japan and go to Nara prefecture you could find the Horyuji Temple, the pagoda of which was built using Shou Sugi Ban and which is widely considered as the “oldest wooden building in the world” (7, 8) – dating back to 711 AD. An example of the effectiveness of the technique! Don’t worry if you don’t have Japan-bound travel plans, though; you can engage in this ancient technique in your own building project wherever you are.
What I learned differs from the ancient art in that the tool I used for the actual charring was an oxygen and propane-powered blowtorch – probably not that common back in the 8th century. Though Shou Sugi Ban is becoming quite popular with architects all over the world and there is quite a lot of online information about it (see for example 1, 9), I have not been able to discover the original technique, though it probably involved directing fire in a similar way to a blowtorch.
Below is a step by step guide of what I did. Many of the steps can be modified according to your materials or preferences so feel free to experiment.
When to do it
This technique can be used for any wooden construction which will be exposed to the outdoors. If you are constructing an entire building you only need to char the wood which will be on the outside so the stage in the building process when you can do the Shou Sugi Ban is just before you build the exterior wooden parts.
Here are the things I used and suggestions for alternatives:
Planks of wood – these can be any shape. I used rectangular planks which had been rescued from a demolished house. It’s recommended to cut the wood to the size you want it before engaging in the charring as it’s possible sawing will interfere with the charred parts and you may have to do it again*
A blowtorch – the one I used (and which Mikale recommends) has 2 pipes which join together in the head of the torch, the pipes leading from separate gas canisters, 1 for oxygen and 1 for propane
A lighter – to light the fire. Very important. Matches could work as well but a lighter is easier.
A brush – for cleaning the wood after charring
Oil and a cloth to apply it – you can use most oil for this. In terms of using natural and sustainable resources non-fossil-fuel-based oil is preferable. We were using canola oil as it’s cheap and widely available here in Thailand. Some commonly-used natural wood-finishing oils are Tung oil and linseed oil
Vinegar to mix with the oil (optional) – this is to repel insects while the finish dries. The vinegar we used happened to be home-made starfruit (Averrhoa carambola) vinegar as there happened to be a lot of it in the place we live; however it seems that the sweetness of the starfruit counteracted the insect-repelling qualities because there were still quite a lot of them around.
1. Set out your workspace
You need to have enough space to hold the blowtorch around 5-12cm above the wood and to direct the flames along the whole length of the plank, or whatever wood you are using. It is advisable to site the place where you will do the charring in a place where there are not too many paths of energy crossing it, for example away from a direct breeze.
It’s a good idea to set up the blowtorch beforehand so you can check the length of the pipe and make sure that you lay the pipe out in a way that there is minimal risk of setting fire to it. Also you can check that the head of the blowtorch is in a comfortable place for you to hold it above the wood, where the pipe is not being stretched.
2. Lay your planks out ready
If you have a large number of planks to char, and the chances are if you’re planning to cover a whole wall there’ll be a fair few, it’s more energy efficient to lay them out ready so that you can move quickly from one to the next. Bear in mind that once one plank is finished it will be hot to the touch and needs a couple of minutes to cool before you can pick it up; if you are wearing gloves you could probably nudge it out of the way or use your foot.
3. Light the fire
Take the head of the blowtorch in your non-dominant hand. Turn the dial of the propane so that it’s slightly open- less than halfway. Then, pointing the blowtorch away from anything it could damage (including your face!) take the lighter and light the flame. The blowtorch will emit a large, orange flame. Carefully turn the dial of the oxygen a little way open.
The flame will turn from large and orange into a concentrated blueish jet. You can fine-tune the jet to get a good balance of oxygen and propane: when the hissing noise is down to a minimum level this is probably a good place. You want the flame to be concentrated, blue and strong enough to burn the wood from around 12cm away. You can always adjust these settings once you start burning, but it’s worth spending a little while fine-tuning the jet from the beginning to get you started in an effective place.
4. Find a distance and start charring
As mentioned, the height above the wood you want to hold the blowtorch is probably between 5 and 12cm away. It depends on your preferences, for example if you prefer to concentrate the flame in a smaller space or prefer to spread it out but with less force.
You can tell when you have the blowtorch at an effective distance when you hold it above the wood in a place where the flame comes down as a blue jet and spreads out on contact with the wood, creating a kind of orange star-like effect through which you can see the sparkling orange charcoals forming.
Once you’ve found this distance, simply begin moving up and down the plank, methodically charring every part of it. If the planks will be touching each other when you put them on your wall you don’t need to char the edge; it’s only the parts which will be exposed to the outside elements that you need to concentrate on.
When the parts which will be exposed to the outside are black that’s enough. Sometimes, especially when you are just beginning, you may char a little overzealously and created burnt ash patches- this is fine as you can remove them when you brush the wood.
5. Allow the wood to cool
Before moving the finished charred planks it’s recommended to leave them for a couple of minutes to make them easier to handle.
Take the brush and rub the charred planks vigourously to remove the excess burnt parts. It’s recommended to do this on the floor or to wear a mask so that you do not inhale these parts. Once the grain of the wood becomes visible you have removed enough and the planks are ready to be oiled.
Before oiling, make sure you have the oil in a suitable container and, if you feel it is necessary, add around 1 part vinegar to 5 parts oil. Take the cloth and dip it into the oil, squeezing it out, then rub it over the planks. This will create a subtle sheen which, depending on the type of wood and the type of oil, can make some very impressive colour effects. Once you have coated all of the planks with one layer, leave them to dry and then apply another coat.
8. Put in place
Now your planks are ready to be put in place. They can last a good hundred years before needing any kind of servicing – after this time you (or your grandchildren) may wish to repeat the process to prolong the preservation.
Now you know how to preserve wood using charring and can apply it to any wooden construction you get involved in. What would you like to char next?
1. Green Spec, 2016. ‘The Environmental Impact of Concrete’. https://www.greenspec.co.uk/building-design/environmental-impacts-of-concrete/
2. Shou Sugi Ban, 2016. ‘The Traditional Art of Charred Cedar’. https://shousugiban.com/
3. Wolchover, N, 2012. ‘Why We Are Drawn to Fire’. Live Science, 23/4/12. https://www.livescience.com/19853-fire-fascination.html
4. Wynn, T, 2012. ‘Fire Good. Make Human Inspiration Happen’. Smithsonian Magazine, 12/12. https://www.smithsonianmag.com/science-nature/fire-good-make-human-inspiration-happen-132494650/?no-ist
5. Jaggard, V, 2015. ‘What the Evolution of Fire Can Teach Us About Climate Change’. Smithsonian Magazine, 2/9/15. https://www.smithsonianmag.com/science-nature/what-evolution-fire-can-teach-us-about-climate-change-180956485/
5. Sterngold, J, 1995. ‘Japan’s Cedar Forests Are a Man-Made Disaster’. NY Times, 17/1/95. https://www.nytimes.com/1995/01/17/science/japan-s-cedar-forests-are-man-made-disaster.html?pagewanted=all
6. UNESCO, 2016. ‘Horyuji Temple’. https://whc.unesco.org/en/list/660
7. Web Japan, 2001. ‘100 Years Older Than Supposed? World Heritage Pagoda’. https://web-japan.org/trends00/honbun/tj010330.html
8. Postgreen Homes, 2013. ‘Shou Sugi Ban’. Youtube, 15/5/13.