Graphite pencils, an essential back-to-school supply, have an interesting history.
For the traditionalist, there is no back-to-school tool more fundamental than the pencil. The standard #2 pencil are used by everyone from kindergartners learning to print their alphabet to high school students filling in circles on a machine-scored, multiple choice test. Most pencils are made of a core of graphite pigment mixed with clay surrounded by a wood case that minimizes the amount of pigment transferred to the user’s hand. The wood case was actually a later innovation; the original sticks of graphite were wrapped in string or wool to reduce smudges.
Graphite has been known since the 16th century, when a deposit of the oily material was discovered in the Lake District of England. Graphite was originally used as a lubricant to smooth the ejection of cannonballs from the shaft of the cannon. The idea of using graphite to mark on paper or wood was not developed until the 18th century. We still refer to the lead in a pencil, but lead was long ago replaced by graphite, which makes a darker mark. The British monopoly on graphite was broken after the discovery of the world’s largest deposit of graphite in Siberia, just a short distance from China. This high quality writing substance prompted a high demand for “Chinese” pencils, so most pencils were given an outer coating of yellow paint, copying the color of Manchu imperial robes, even though the pencil material may not have come from that original source. Even today, a majority of the pencils sold in the United States are painted yellow.
Pencils are rated on a B scale for Blackness and an H scale for hardness. Thus, a 9B pencil produces a dark black smudgy mark and a 9H results in a light colored, easily erased line. This characteristic is adjusted by using more or less clay mixed in with the graphite. More clay results in a softer core and more graphite being rubbed off on the paper giving a darker line, but the pencil will also dull more rapidly and will require sharpening more often. The #2 pencil is at the middle of both scales and is intermediate in both blackness and hardness.
Although the pencil may seem old-fashioned, its equal effectiveness in normal gravity and zero gravity make it a first-rate writing implement for astronauts in outer space. More information about this versatile historical and futuristic device may be found at http://www.pencils.com/learn