Most people aleady know that the "lead" in pencils has been made of non-toxic graphite for some time now. A more obscure story is that the Mad Hatter depicted in Alice in Wonderland is based on the tendency of many hatters to go insane after handling so much mercury in the hat making process.1 How come we never hear of the Sickly Scribe? Most likely this is because the lead does not permeate the skin as readily as mercury. With the discovery of graphite, pencils evolved in two ways. First, they stopped killing you or making you sick and, because the graphite was more brittle than lead, they were encased in first string and then wooden rods that had to be hollowed out by hand. They left a darker mark and were easier to handle.
Graphite also has a history apart from pencils. It's discovery was made, not by scientists, but by shephards after a severe storm in Borrowdale, England in 1564. Encountering a large deposit of a black substance that wouldn't burn like coal, the shepherds were baffled. They soon discovered that it was an excellent way to mark their sheep. The English government soon found uses for it, chiefly for cannonball molds during the reign of Elizabeth I. It was termed 'Wad' and the smuggling of this useful substance was deemed a felony in 1752 by parliament.
As an artistic medium graphite is cheap, readily available, and one of the easier mediums to use. Like most artistic endeavors, to master it requires stringent discipline. Like watercolor, the use of graphite is heavily influenced by the type of paper used. Although graphite can be applied to canvas, this is usually only to create a guide for the application of another medium such as oil or acrylic. Personally, I find that watercolor paper allows for the greatest range of expression with a pencil, though at times it is hard to get the darkness afforded by other papers. Unlike watercolor, however, graphite allows for the representation of the most minute detail.
Graphite pencils come in a range from very hard to very soft. This large range is possible because of the Conté Process, where a ratio of clay particles and graphite are mixed. More clay equals a softer and darker pencil. The full range is designated using B for black (or soft) and H for hard, and goes from 9B to 9H. The #2 pencil that standardized tests are so fond of reside in the middle with an HB grade. There have been variations on this scheme though, incorporating the letter F as well. Because of this extreme range, a graphite drawing can take on photo-realistic qualities in the hands of a master.
thanks to sid
for informing me that there's more to this story than I've given here. Check out www.snopes.com/language/phrases/hatter.htm for the details.