Richard Dowsett shows how charcoal can be made on a small-scale without any fancy equipment.
This exhibit shows the method I have developed to make charcoal for drawing. Any wood can be used to make charcoal but I have found willow to be the blackest; hazel gives a brownish tint and elder bluish. The smallest scale that I have found practical is a treacle tin, but sweet or biscuit tins produce a good quantity.
Select straight twigs and cut to length omitting knots and any badly bent sections. It makes life easier if the raw material is the same or similar thickness as this makes baking more consistent.
For younger children I use thicker twigs and under-bake so there is something positive to hold.
After filling the tin (you can keep different species separate by partitions of paper, which survives as wafer thin charcoal sheets) put the perforated lid on and place on an established fire with good embers. It is absolutely essential that there are enough holes in the lid to accommodate the expanding gas and for volatiles to escape without exploding the tin.
The photo below shows a tightly packed kiln with segregated charcoal sticks. Willow, ash, elder and hazel are present. Note the holes in the lid to let the expanding and combustible gases out
It is easy to underestimate the heat in the tin when cooked and in the charcoal once cooking is completed. A tin that is cool enough to handle will almost certainly have an interior hot enough to spontaneously combust the charcoal when the lid is removed. Keep a bucket of water close.
Due to the lack of oxygen the wood cannot burn but the gases will ignite once they mix with oxygen. Once this “birthday cake effect” is over and all smoke has gone, the hot tin can be lifted off the fire using tongs and dowsed until the temperature in the middle of the tin is low enough.
This stage is crucial: if there is too much residual heat, the sticks will oxidise and catch fire. The safest way is probably to submerge the whole tin under water or to swamp the charcoal sticks. The art is to use enough water to quench but such that it is evaporated to leave dry sticks. Otherwise the tin and contents can be cooked to drive off the water before setting light to them.
A blackened biscuit tin containing charcoal. Water has been added to cool it down.
The charcoal is now ready for use.
The tedious part is stacking a tin so do not underestimate the time needed. The willow can be stripped but it is not essential. Allow 45 -60 mins for the baking, dependant on the fire you are using. Do not skimp on the cooling/dowsing stage.
Keep the process safe and have fun.