Conté Pencil
The history of the modern graphite pencil is closely connected with the French artist, engineer, and inventor Nicolas-Jacques Conté. In 1795, he developed a method of making pencil cores from powdered graphite mixed with clay.
Why was a new pencil-making method needed?
One of the most famous sources of high-quality natural graphite was the Borrowdale deposit in Cumbria, England. Its graphite was unusually pure and could occur in dense masses that were useful not only for writing and drawing, but also for industrial purposes.
Graphite was used in metallurgical work and for treating moulds used in the casting of cannonballs and musket balls. This gave high-quality graphite considerable economic and military value.
The British Parliament passed legislation intended to discourage unlawful entry into graphite mines and the theft of valuable graphite.
During the wars involving Revolutionary France, access to high-quality English graphite became difficult for France.
Nicolas-Jacques Conté developed a method of producing pencil cores from powdered graphite and clay, followed by heat treatment.
It is sometimes claimed that the British Parliament imposed a complete ban on graphite exports in the late eighteenth century. The well-documented Act of 1752, however, primarily dealt with unlawful entry into graphite mines and graphite theft. These two claims should not be treated as the same event.
What did Conté develop?
Instead of relying on solid pieces of natural graphite, Conté used finely powdered graphite mixed with clay and water. The mixture could be shaped into thin cores, dried, and fired.
Graphite and clay are reduced to very fine particles.
The materials are mixed with water to create a formable mass.
The mixture is formed into thin rods that will become pencil cores.
After drying, the cores are heated, giving them greater mechanical strength.
But does clay not become hard when it is fired?
Yes. That is one of the reasons clay is useful in a graphite pencil core. During firing, the clay develops a harder mineral structure that helps bind the graphite particles together.
When the pencil moves across paper, the microscopic roughness of the paper gradually removes tiny particles from the core. Graphite-rich material remains on and between the paper fibres, producing the visible mark.
Why change the amount of graphite and clay?
One of the great advantages of the graphite-and-clay system is that the properties of the pencil core can be adjusted by changing the composition of the mixture.
More graphite → softer and darker
Softer pencils transfer material to the paper more easily and usually produce darker marks. In the modern grading system, these pencils are generally found in the B range.
More clay → harder and lighter
A greater proportion of the clay component generally produces a harder core that leaves less material on the paper. These pencils belong to the H range.
Manufacturers use different formulations and production methods. An HB pencil therefore does not necessarily contain one fixed, internationally standardised percentage of graphite and clay. The grade describes the practical characteristics of the pencil, not one universal chemical recipe.
In short
- natural graphite was used for drawing before Conté;
- graphite from Borrowdale in England was especially valuable;
- in 1752, Parliament strengthened legal protection against unlawful entry into graphite mines and graphite theft;
- in 1795, Nicolas-Jacques Conté developed a method of making pencil cores from powdered graphite and clay;
- changing the composition of the mixture makes it possible to produce pencils with different degrees of hardness and darkness.
Sources
- British Library, The History of the Pencil
- Historic England, Borrowdale graphite mines and associated grinding mill
- British Geological Survey / NERC, The graphite deposit at Borrowdale (UK)
- British Art Studies, Turner’s Pencil: Graphite Landscapes and Extractive Industry