Charcoal is traditionally made from thin peeled willow twigs which are heated without the presence of oxygen. This produces black crumbly sticks, which leave microscopic particles in the paper or textile fibres, producing a line that is dense at the pressure point, but more diffuse or powdery at the edges. The overall result is less precise than hard graphite pencils, so charcoal is suited to freer studies. Charcoal smudges easily and is often protected with a sprayed fixative.
In the twentieth century a processed version was developed, called compressed charcoal.