Mine (pencil)

The mine of pencil is thin a Cylindre, generally surrounded by Bois, which leaves on the Papier a trace that one can generally simply erase with the gum. The word is resulting from the Gallic meina indicating a rough metal.

History of pencil lead

Indeed, the first pencils, used as of the Roman epoch, used a black lead (or out of money).

Starting from the the Middle Ages, the lead pencil replaces the feather and ink for the fast writing and remains used until the 19th century. In fact one uses an alloy of Plomb (2/3) and of tin (1/3). Its tendreté made its success until the Graphite shows same qualities.

This alloy being friable, as of this time one reinforces it then one surrounds it by wood: the pencil was born.

Lead will be competed with by the " Black lead " following the discovery in England of a site of very pure graphite extraction (regarded a long time as lead ore, of or its name).

An effective amalgam between less pure graphite and Clay, developped at the point by Nicolas-Jacques Told, replaced black lead. One surrounds it by wood of lime, spruce or cedar for beautiful the pencils.

The improvement of this material by Lothar von Faber allowed the development of a broad range of hardness.

For a few years, the Conté company has invented a plastic mine, therefore perfectly unbreakable.

Manufacture of the mines

The black mine is carried out starting from a mixture of powder graphite combined with a mixture of Kaolin and Bentonite (aluminum silicate) in the presence of water. The paste is dried, then cooked towards 1200°C.

The mines of color contain mineral Colorant S sensitive to the high temperatures, they are not cooked but are étuvées, and are not reinforced with other binders.

The mines are then stuck in the grooves of a small plank out of wooden, then covered with a second grooved small plank stuck on the first.

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