The oil I see used most often on charred wood is Penefin, which is available in many of the big box stores. Another one I’ve used in the past is Sikkens. Cabot is yet another brand I’ve used (mostly for decks).
Any semi-transparent wood stain should work. If you go with a brushed char finish, you may want to experiment with color options to see what kind of effect it may have on the final finish (the semi-transparent stains typically come in a range of subtle color choices).
In our case, we decided to use Tung Oil mixed with Citrus Solvent (available from: realmilkpaint.com). Having used it previously on arts-and-crafts projects with good results, and because it’s considered No VOC, we felt it was a good choice (although not the cheapest option). We’ll also be using the same combination of products for our hardwood flooring.
We used a 1:1 mixture of Tung Oil and Citrus Solvent (they even sell it this way, pre-mixed, if you don’t want to deal with combining individual batches together). The Citrus Solvent acts like a traditional paint thinner (without the VOC’s or strong chemical smell), diluting the Tung Oil so it can more easily soak into the wood (it also smells great since it’s made from orange peels). The Citrus Solvent is also used for cleaning up tools, equipment, and any spills of the tung oil (also works great as a general purpose degreaser — especially above and around a stovetop).
USE CAUTION! — Although natural and safe, the Citrus Solvent can irritate bare skin. I always use either Latex or Nitrile gloves (readily available at any hardware store).
If you try using the Tung Oil alone, the difference in performance is obvious (the oil will mostly just sit on the surface, with little of it soaking in — a frustrating waste of time and money).
I decided to use a trough for dipping each board based on a project I saw online:
Their house and blog caught my attention early on, when we were just beginning to think about building new. Their project, along with several others, really got me excited about the possibility of building “green”.
GO Logic (Red House project; featured in the video below)
Spartan and Hannah’s home (zeroandbeyond.com) is an excellent example of the Pretty Good House concept, and it’s definitely worth checking out, especially under the heading of Presentations: How to Build an Affordable Net Zero / Super Energy-efficient Home(pdf).
A lot of great information to get you thinking about exactly what it is you may want to build, and how to financially pull it off. They also have a lot of thoughtful and inventive design elements (love their granite floor built with cut waste from various countertop jobs — a very creative idea with a unique look).
Anyway, back to the trough: It’s much faster than trying to use a brush or roller, and it guarantees full coverage (many thanks to Spartan & Hannah for posting this simple, but time saving idea).
Below is my version of the same thing:
Once in the trough, we would let each board sit for about 30 seconds in the Tung Oil and Citrus Solvent bath, before pulling it up and resting it on the 2×4 ledge. Seated on its perch, the board would get wiped down initially with just a squeegee.
At this point, we would walk it over to the drying rack.
Once on the rack, we would use a brush to apply an additional coat of Tung Oil and Citrus Solvent, but only to the rough side, since it will be exposed directly to the elements.
After about 20 minutes on the drying rack, we would wipe down both sides of each board (the most laborious part of the job). Usually by the time you’ve placed the tenth board and brushed it, the first board is ready to be wiped down. We found that dust free cotton rags are the best option for this.
Typically, there’s not much oil left on the surface, as most of it has soaked in. The wiping just removes any excess that could cause an unwanted film to form on the surface of the wood (not attractive).
The only real down side to the wiping (apart from the time, energy, and the cost of the rags) is that it makes the boards more uniform in appearance — in other words, some of the texture in the gator look is lost due to the wiping. Nevertheless, this comes with an added benefit, namely, removing any char that might otherwise flake off in the first couple of rainstorms.
When the boards are finished and completely dry, the finish looks very durable (and sleek).
Depending on temperature and humidity, it takes roughly a week for the boards to be dry to the touch.
It’s the wiping down of each board that requires some real elbow grease – no surprise my daughter disappeared at that point in the process (can’t blame her, it’s tedious work).
As long as you have at least two people working together — pulling boards, dipping, transferring to the drying rack, and then wiping down — the process isn’t too bad. Going solo would get old very quickly. It’s even better if you have a couple of people just setting up the drying rack and wiping down while a third person pulls boards and dips.
There’s no question the process takes time and effort, but the results are unique and, we think, very beautiful.
September, 2019 Update: To see how the charred cedar turned out on the house, go here:
There’s some flexibility in exactly how it’s done, and there are various looks that can be achieved. For example, we’re going for mostly a “gator” finish, meaning the cedar will have an alligator skin-like appearance. This is considered a heavy burn.
An alternative way of doing it would be to “gator” it first with fire, then scrape the excess char off, leaving behind a smoother, lighter, but still charred and protected finish (see video below).
Here are a few pictures that highlight the difference:
Once the charred wood has been oiled (whether it’s with a gator finish or a brushed finish), it will look something like this:
There are companies in the US that are exploring the limits of what can be done with shou sugi ban, including the use of various species of wood, a range of options in the level of char, and potential areas for its installation:
Either way, the char doesn’t go very deep into the wood, and it doesn’t have to in order to be effective — either for looks or durability.
For instance, once the wood has been charred, it will be fire resistant. The charred surface actually protects the wood from further burning. I had to see this to believe it, but if you char a piece and then hold the torch in one spot it really does resist burning (you can eventually reduce the wood to ash, but it takes a surprisingly long time).
The charred wood will also be unappetizing to insects or rodents, and once covered in its attractive black armor, the surface can face decades of sun and rain (80-100 years is the usual claim for its longevity) with little or no maintenance, apart from an occasional fresh coat of oil (every 15 years or so?).
Our wall assembly will utilize a fairly substantial rain screen, meaning there will be significant air movement behind the siding, so one could argue it should be unnecessary to char the back of each piece, but we’ve chosen to do so for the added peace of mind (and not a really significant amount of additional time — and the charring is fun to do anyway).
For cut ends and mitered joints, we will use tung oil to help seal these areas (similar to painted wood siding that gets a swipe of oil based primer in these same spots just before installation).
Once charred, the wood can immediately be installed, or, as we’ve chosen to do, you can oil it first. After experimenting a little back in 2015, applying an oil finish seems to bind the char to the wood better than leaving it just “as is” (regardless if the level of char is light or heavy).
Also, if you don’t oil, then the surface remains like a charcoal briquet, so any time it’s touched some of the char will rub off — just imagine the reaction of friends or family the first time someone leans against the siding, or if you have kids running around and they touch the char. It could be a real mess.
In addition, if you choose not to oil, then every time the charred wood is cut during installation black dust will go flying (whoever does the installation will not be pleased when their hands, bodies, and lungs are covered in a layer of fine soot — picture a 19th century Welsh coal miner).
So for durability, looks, and ease of installation, we’ve decided to take the extra step of oiling each piece as well (more about this process later).
There is a range in the level of char we want to achieve. While most boards will have the gator finish, much lighter boards (a few even lighter than the one pictured above) will be part of the mix as well. We think this will make for a more interesting overall look, but it also takes the pressure off, slightly, if you have more than one person doing the charring (each person will have a slightly different definition of ‘gator’).
We’re also curious to see how the lighter boards will age with time: Will the lighter undertones of raw cedar turn gray and blend nicely with the char? Or will the natural color, peeking through the black surface, stick around longer than we think?
As far as the tools involved, the following have worked for us:
We were planning to use the typical 40 pound propane tank that’s used for grilling. Fortunately, my wife was smart enough to look around online for us, and she found these 100 lb. tanks instead.
These 100 lb. tanks have worked out great — no trips to a big box store for refills on the smaller tanks. And by buying the gas in bulk, they’ve also saved us some money as well.
You can follow the level of the tank by looking for condensation. The only down side to these larger tanks is once they hit this level, about 1/4 full, pressure drops significantly, so it takes twice as long to burn a board.
Here are some of the key connections involved:
The Inferno comes with a 10′ hose, which works okay, but we bought a 25′ extension hose on Amazon that definitely makes life easier by allowing you to get further away from the tank for a wider range of motion.
In terms of safety, in addition to a pair of sunglasses or construction safety glasses, proper hearing protection is a must. If you’re doing just one or two boards, the noise level of the torch isn’t a big deal. However, if you plan to do dozens of boards at one time, we would definitely recommend some kind of hearing protection. The torch is undeniably loud (we’re lucky we have patient, forgiving neighbors).
Welding gloves have also been a real help. On windy days, the boards tend to stay lit longer, but it’s easy to just pat or rub out the small areas of flame with the welding gloves. And they’re a must for moving the boards around right after charring.
We also keep a couple of 5 gallon buckets around, only partially filled, so it would be easy to toss it at someone who’s just burst into flames (let’s hope this never happens).
In addition, we have a 6′ step ladder set up as a station to hold the torch when not in use, and it’s a convenient spot to drape a garden hose with a nice spray nozzle, so it’s in easy reach if something should go wrong. We also occasionally spray down the concrete, hoping this discourages any stray embers from landing and then floating away to ignite something in the surrounding area.
To be honest, the only time I got myself in trouble was when the 100 lb. tank was 1/4 full and the pressure had dropped. Normally, we barely have gas running through the hose and coming out of the torch because the boost switch on the torch is so effective. Because of the pressure drop, I turned up more gas, hoping it would counteract the loss of pressure, but instead I just managed to catch my jeans on fire at the knee (momentarily, thanks to a handy 5 gallon bucket of water). I was extremely lucky, and lesson definitely learned.
Right as the sun is going down is the most exciting time to burn — the flame becomes vivid, and it’s really fun to watch as it dances across the surface of the board.
The 1x material, whether 1×6 or 1×8, takes longer to burn since we found it impossible to get the face and the edge all in one pass. You can definitely pick up more of a rhythm with the 1×6 T&G boards. And we haven’t gone for a gator appearance on the back (smooth side) of each board, instead going for a lighter char, which also helps to speed things up for each board.
How much will all this cost?
How long will it take?
For our single story, just under 1700 sq. ft. house (outside dimensions), with an attached 2-car garage, these are how our numbers break down:
Time to burn (per board): about 1-2 minutes a side
In 6-8 hours, 40-80 boards is realistic (depends on level of char, and if it’s 1x or T&G)
Total time to burn all the boards we should need: ±80 hours
For torch, hearing protection, welding gloves, extension hose: $100-150
Per 100 lb. tank: $80-90 (8 total tanks to finish).
1×2’s, or similar material, for stacking the completed boards: $100-200
#3 or better Cedar (1×6 T&G, 1×6, and 1×8): approx. $8-10,000
Keep in mind, this doesn’t include the time or expense required to oil each board (again, more on that later).
One final, additional challenge was getting quality boards.
Our first order of cedar, via a big box store, came from Mary’s River (they’ve either gone out of business, or their manufacturing plant burned down — depends on who you ask). Their rate of waste was about 10-15%, so not bad at all. It felt like I had to go looking for bad boards (board bends to the left or right at the end, U-shaped from the middle, broken or missing tongues/grooves, or cracked/split boards).
In subsequent orders, with a company called Tri-Pro, the rate of waste was about 40%. Luckily, the big box stores are okay with returns, nevertheless this gets frustrating.
And even with the big box stores themselves, there can be significant differences in quality from one location to another. Our first couple of orders were poorly packed and just wrong. Then, after going to a second location to order, in Long Grove, this showed up:
I can’t tell you whether the person (or persons) who put this specific pallet together actually enjoys their job, but what I know for sure is that they give a shit (to be perfectly blunt).
Unfortunately, this level of quality and pride in workmanship is exceedingly rare — anywhere, in any occupation — so when you see it, it can’t help but stand out and grab your attention.