Thursday, April 28, 2005

Lead of a pencil

The pencil lead, as it is known today, is actually not made of lead. The traditional material used to make the pencil lead is actually a mixture of Bavarian clay (or, to a lesser extent, Georgian clay) and graphite from Sri Lanka, Madagascar or Mexico. The above mixture is bound together with waxes from Brazil or Mexico and gum Tragacanth from Asia. The wood used to encase the pencil lead in the Americas is generally derived from cedar from California, Oregon and some parts of Nevada. On the other hand, white pine and basswood are the preferred pencil wood in Russia and China respectively.

The purest graphite discovered was revealed in 1564, when an oak tree fell during a storm near Borrowdale, England. The shepherds in the area found the rough chunks to be useful to mark their flocks, but the raw material was also very dirty and messy to handle. That problem was addressed by cutting the material into square pieces and encasing them with wood. The material discovered was called "plumbago" (imitation lead). In 1779, K. W. Scheele, a Swedish chemist, found "plumbago" to be a form of carbon and suggested that it be called "graphite" from the Greek word for writing. The first hand made pencils, in the form that we know today are the "Crayons d'Angleterre", made from Borrowdale graphite. One year after the discovery in Borrowdale, Conrad Gesner of Zurich, wrote the earliest surviving description of a pencil in his Treatise on Fossils, illustrated with a woodcut by the author showing a wooden tube holding a piece of graphite. Some scholars believe this "Gesner pencil" was used by Shakespeare.

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