The pencil

How a lump of black mineral became the world's most familiar writing tool

Around fourteen billion pencils are manufactured every year, enough to circle the Earth dozens of times. Each one, it is said, could draw a line more than fifty kilometres long or write some 45,000 words before it was used up. Yet few people who pick up a pencil know much about it, and the one thing that most people think they know is wrong: the dark core, universally known as the 'lead', has never contained any lead at all.

The story begins in the north of England in the middle of the sixteenth century. According to local tradition, a violent storm blew down several trees on a hillside near Borrowdale, in what is now the Lake District, and exposed a deposit of a strange black material beneath their roots. Shepherds soon discovered that it left a dark mark and began using it to identify their sheep. The substance was graphite, a form of carbon, but chemistry was in its infancy, and it was assumed to be a kind of lead. It was called 'black lead', and the name has never quite gone away.

Borrowdale graphite was remarkably pure and solid, and could simply be sawn into thin sticks. These were soft and dirty to handle, however, so users wrapped them in string or in sheepskin to keep their fingers clean. A better solution appeared in Italy, where craftsmen hollowed out a stick of juniper wood and pushed the graphite inside. Some time afterwards came the idea of carving a groove in one strip of wood, laying the graphite in it and gluing a second strip on top. With minor refinements, this is how pencils are still made today.

The Borrowdale deposit was the only source of such high-quality graphite then known in Europe, and its value rose further when it was found that the material could be used to line the moulds in which cannonballs were cast, producing smoother and rounder shot. The English Crown took control of the mine. Armed guards escorted the graphite to London, and when enough had been extracted the workings were deliberately flooded until more was needed. Despite a law of 1752 that made theft from the mine punishable by hard labour, smuggling was common.

Pencil-makers elsewhere had to manage with poorer material. In the German city of Nuremberg, where a pencil industry had grown up in the 1660s, craftsmen ground low-grade graphite to a powder and bound it together with sulphur. The results were scratchy and unreliable. The decisive advance came in France. In 1795 the country was at war with Britain and could no longer obtain English graphite, so the government asked Nicolas-Jacques Conté, an army officer and inventor, to devise a substitute. He is reported to have found the answer within days. Conté mixed powdered graphite with clay, pressed the paste into narrow rods and baked them in a kiln. The process not only made a small amount of graphite go a long way; it also allowed the maker to control the result. The more clay that was added, the harder the pencil and the paler its line. Every graded pencil sold today, from the softest 9B to the hardest 9H, is a descendant of Conté's invention.

In the United States, early pencils had a poor reputation, and those who could afford to bought imported ones. One of the firms that changed this belonged to John Thoreau of Concord, Massachusetts. His son Henry, who would later become famous as a writer, studied European methods and worked out how to make a clay-based core of his own, and for a time Thoreau pencils were considered the best in the country. A further American contribution followed in 1858, when Hymen Lipman of Philadelphia patented a pencil with an eraser fixed to one end. The idea was an immediate commercial success in America, although in Europe pencils without one remain common to this day.

The familiar colour of the pencil has a history too. By the late nineteenth century, the finest graphite was coming from the Far East. In 1890 the Hardtmuth company of Austria-Hungary launched a luxury pencil named after a celebrated diamond, the Koh-i-Noor, and painted it yellow, a colour long associated with royalty in China, to advertise the origin and quality of its contents. The pencil sold so well that competitors hurried to imitate it, and yellow became the standard.

Modern pencils are made chiefly from cedar, which is soft enough to sharpen easily and does not splinter. Thin slats are grooved by machine, the cores are laid in place, a second slat is glued on top, and the resulting 'sandwich' is cut into individual pencils and painted. For all the competition from pens and keyboards, the product survives because of what it can do. A pencil needs no ink or battery, its marks can be removed, and it will write upside down, in freezing temperatures and even in space, where the first astronauts and cosmonauts carried them. Few inventions have changed so little, or needed to.