Charcoal
Charcoal is made from wooden slips bound together and carbonized in an airtight container, so that they do not burn to ashes. What remains are friable sticks, which leave long, sharp-edged particles in the paper fiber, producing a line denser at the pressure point, but more diffused at the edges than black chalk, because of its friability. The overall result is less precise, ideally suited to freer figure studies and heads. It is also the most easily erased of media, making it ideally suitable for underdrawing.
 


Odilon Redon. Untitled. Art Market

 

by Michael Miller
Information supplied by: http://www.nyu.edu/classes