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Stumper #42

a. What is this substance in a pencil that naturalists, artists, writers, engineers, architects, scientists, and just about everybody young and old, use to express themselves on paper?
Answer: graphite

b. What do pencil makers do to this substance (revealed in a.) to create pencils of different hardness?
Answer: Graphite dust is mixed with varying amounts of clays to create soft and hard pencils.
This technique was developed in France in 1795 when Nicolas Jacques Conté discovered that graphite ground to a fine powder with clay and fired in a furnace was more adaptable for use in pencil making than pure graphite.


Early “pencils” such as had been used for centuries were described in the 1771 Encyclopedia Britannica as instruments used by painters. The larger sorts were made of boars’ bristles bound to a stick and were also called “brushes” while the finer pencils were made of camel, badger or squirrel hair. However, by 1771, but not mentioned in the encyclopedia, other types of pencils were being made in the form of wood-encased strips sliced from mined blocks of graphite.

There are about 2.8 billion pencils used in the U.S. every year.  The average pencil can draw a line 35 miles long or write about 45,000 words.

The Thoreau pencil company mentioned in the stumper used high quality graphite from a deposit discovered in a New England by Thoreau’s brother-in-law.
What is Graphite?

Graphite (also sometimes called plumbago or black lead) is pure carbon generally in hexagonal crystals. At surface temperatures and pressures, Graphite is the stable form of carbon. It is black, soft, and has a metallic luster but is not a ‘metal.’ It came into use by writers and artists in the 16th century when a large deposit was found in Borrowdale, England. Sticks of the newly discovered substance were wrapped in string and used for drawing and writing on paper.

Graphite is what is known as a polymorph of the element carbon. Another well known polymorph of carbon is diamond. The two share the same chemistry but have very different structures and very different properties. Diamond is hardest mineral known to man, Graphite is one of the softest. Diamond is usually transparent, Graphite is opaque. Diamond crystallizes in the Isometric system and graphite crystallizes in the hexagonal system.

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