Charcoal making – a brief overview
Charcoal is like alchemy. You take a stick, heat it up in an environment without oxygen, and hey presto, it turns into ‘black gold’. Here is a bit more detail on how it works and how to do it!
Burning wood requires three things: fuel (the wood); heat; and oxygen. As wood burns in a fire, the ‘organic compounds’ (chemicals made of carbon and hydrogen, among other things) are literally boiled out of the wood. This is ‘woodgas’. In a bonfire some of this woodgas is burned giving us red/orange flames in fire*. However, much of the woodgas cools and forms smoke. As the fire burns, it gives way to ‘glowing embers’ that remain long after the flames have disappeared. This is the remaining carbon, in the form of charcoal.
The embers – charcoal – carry on burning as they access oxygen, gradually reaching the centre of the fire. When they have burned only ash remains, which is the inert, incombustible minerals in the wood. Find out more in this Blog post about what ash is and whether it’s a good indication of ‘how good’ your stove is. (Spoiler alert: It’s not!)
Turning wood into charcoal
Quick revision: fire needs fuel; heat; and oxygen. Making charcoal takes the first two but excludes the last. It’s an art and science.
Most charcoal is made in the same way: you enclose wood in an environment with no, or limited, oxygen and heat it up. The organic materials boil off, leaving just carbon. The resulting product yields anything from between about 20 – 60 % of the original mass of wood, and is usually about twice the energy content per kg.
Traditional charcoal makers use a large steel drum to control air supply, or just build up a pile of logs, light them, then enclose the whole lot in soil. This contains the wood in an atmosphere with limited oxygen.
How to make artist charcoal – a brief DIY guide
⚠️ Read the bit about LOOSE fitting lid carefully!
To make artist charcoal we are simply making charcoal on a tiny scale.
- Fill a tobacco tin or old biscuit tin with sticks. Any sticks will do, and it’s fun to see the different effects from different species. It doesn’t have to be seasoned, though cracks less if it is.
- Close the tin with a LOOSE fitting lid, and put the whole tin in a fire. It is VITAL you use a tin with a loose fitting lid, otherwise the gases produced may cause your tin to explode. You can place it in a your woodburner, or on a bonfire in the garden.
- Enjoy watching the woodgas start to seep out from the tin, and eventually catch fire as it heats up!
- Once no more smoke emerges, your charcoal will be done. This usually takes about 20 minutes, but is very dependent on the heat of your fire, the wood moisture content, size of tin and so on.
- Now, remove the tin from the fire (using tongs or some such) and WAIT. Don’t open the lid while it’s hot, or oxygen will find the hot charcoal sticks and turn them into ash!
- Once well cooled, open up your tin and smile to yourself as you reveal your unique charcoal.
That’s it. Please share your experiences in the comments below, or feel free to ask any further questions. Some people pack the tins with sand to stop the sticks warping. Some people swear by willow. Have a go!
Look out for our workshops
We run free workshops making artist charcoal at various festivals through the summers. This year we’ll be at Buddhafield and the Green Sycthe Fair, among others to be announced here on the Blog. We also use it as an excuse to get really geeky about what combustion is, biochar, carbon cycles, and global emissions and public health related to burning wood. It’s quite broad!
The best bit is you get to wonder off with some black gold…
* Some of our woodgas stoves use this to great effect by producing, and then burning, the woodgas, hence produce very little smoke.