Graphite pencils took the place of lead and silver metalpoints for rendering fine linear drawings, hence the familiar terms “pencil lead” or “lead pencil” (even though pencils contain no lead whatsoever). After its discovery in sixteenth-century England, natural graphite was so highly prized that by law it could be mined only six weeks a year, and was transported to London by armed guards. In the late eighteenth century, French inventor Nicolas-Jacques Conté patented a substitute for natural graphite. His formulation consisted of powdered graphite mixed with clay into a paste, then shaped into rods and fired like ceramic ware.
The proportions of clay and graphite can be varied to produce grades of hardness, categorized as H, F, B to indicate Hard, Firm and Black. Graphite is also available in stick and powder form, as shown at the top of the above illustration.
