One of the most basic of all drawing materials, known since antiquity. A wood carbon formed by slowly heating bundles of twigs in airtight chambers, a process that produces charred wood rather than ash. Because charcoal is composed of large, almost weightless, particles and is both very fragile and friable, allowing it to be erased with even the gentlest of rubbing, it is most suited for broad, rapid preliminary sketching on canvas, panel, paper or wall. The overall result is less precise than hard graphite pencils, suited to freer studies. Charcoal smudges easily and is often protected with a sprayed fixative. It is used to make both sketches and finished works, and as under-drawing for paintings. In the 20th century a processed version was developed, called compressed charcoal. (Hans Burgkmair, Head of a Bearded Man Wearing a Turban). In order to obtain a more intense and durable black stroke, the charcoal was occasionally soaked in linseed or olive oil to create ‘oiled charcoal’. Powdered charcoal is used to transfer drawings to surfaces by dusting through ‘pounced’ lines on the drawing.