Making Charcoal for Drawing

Here’s some tips on making charcoal for drawing.

I don’t particularly like using thin sticks of fragile commercial willow charcoal, I much prefer big chunks made from bits of trunk. You can drag it roughly all over a surface with abandon. You can split it into crude lumps and use the edges for line and the sides for blocking in tone.

First gather your wood –

I’m trying out some apricot and olive wood. I’ve had success in the past with willow and pecan (hickory) woods, but am always on the lookout for something different. It needs to be a fairly soft pithy wood, without much in the way of heartwood.

It’s best to start with green wood, as the bark peels off easier, then leave it to season for a year or so to remove the water (or use a microwave). Firing wet wood can result in a lot of cracking and bending of the charcoal. You need to peel off the bark (and scrape off any cambium layer), as it will be hard and scratchy when drawing with it. Willow is particularly easy to strip. In this case I’m going to fire green wood. Here’s the stripped wood packed in an old heavy cast iron pot that gives good results –

Some pack the pot with sand to help stop the wood from bending too much. This is only a problem if the wood used is small branches and is wet. Many people just use a tin can with a tight lid and a small hole punched in the top, but I find the heavier container better as it spreads the heat more evenly. Camp ovens work well. Next the pot goes in the fire –

The loose lid prevents oxygen getting into the pot and burning the charcoal to ash, while letting the volatiles escape. No peeking during the process, or before the pot cools, as the oxygen will combust the charcoal. This is a reduction (pyrolysis) reaction, “burning” in the absence of oxygen, removing the volatiles and leaving the carbon, as in cooking in an oven. I’ve made charcoal simply by baking over a couple of days in a wood oven. Brown, half burnt charcoal can also be made in this way, but it’s a bit hard. Damp the fire down. After a while the water starts to escape –

And later the volatiles are driven off, igniting as they escape –

And next morning here’s the result –

Nice big chunks of charcoal that I prefer to use, which are easily broken up into smaller pieces as required. The splitting is typical of charcoal made with wet wood.

Unfortunately this charcoal was useless for drawing, being a bit hard and scratchy. So I crushed it up and used it as biochar on the garden. I’ve since made a batch with river oak, which was quite good, and a batch from a long dead and very dry stone pine, which was very good. You can see the difference in the cracking when the wood’s dry (less shrinkage) –