Pencil lead is not lead. People once thought graphite was a kind of lead, so they called it black lead. That is why we still say pencil lead. In 1779, scientists showed it was really carbon. The name graphite comes from a Greek word meaning to write.
Graphite is made of tiny layers of carbon. The layers slide apart easily. When you drag a pencil over paper, flakes rub off and leave a line.
Early graphite sticks were wrapped in string or sheepskin. In the 1500s, graphite was found near Borrowdale in England's Lake District. It became the first big graphite mine.
In the 1790s, a French engineer named Nicolas-Jacques Conté found a new way to make pencil cores. He mixed graphite with clay and baked it.
Today pencil makers push the graphite and clay mix through a small opening called a die. This makes long, thin rods. The rods are cut to length and baked hard in a kiln.
The more clay in the mix, the harder the pencil. The more graphite, the softer and darker it is. Hardness numbers run from No. 1, the softest, to No. 4, the hardest. Most students in the United States use No. 2 pencils.
Many pencil makers use incense-cedar, a tree that grows in California and southern Oregon. It is a very steady wood. It holds its shape and does not warp when the heat or damp changes.
Thin boards get grooves cut into them. The graphite rods lie in the grooves, and a second grooved board is glued on top. The wood is then shaped and cut into pencils. Many pencils are six-sided because a round pencil rolls off a desk.
Many pencils are yellow, especially in North America. One story says a fancy pencil called the Koh-I-Noor, shown around 1890, helped make yellow popular.
Words to know
- graphite: soft black mineral
- carbon: an element
- kiln: baking oven
- die: shaping hole
The short version
A pencil's core is graphite mixed with clay, not lead. Pencil makers lay graphite sticks in grooves in a wooden board, glue a second board on top and cut the sandwich into pencils. More clay makes a harder pencil, and more graphite makes a softer, darker one.
Quick facts
- Graphite and diamond are both made of carbon, but they look and feel different.
- In 1779, scientists showed pencil lead was really carbon.
- The Frenchman Nicolas-Jacques Conté mixed graphite with clay in the 1790s.
- Many pencils are made from cedar, which does not warp.
- A No. 2 pencil is the one used for most writing.
Is there lead in a pencil?
No. The black core is graphite mixed with clay. People once thought graphite was a kind of lead, so they called it black lead, and we still say pencil lead. In 1779, scientists showed it was carbon.
How do they get the lead into a pencil?
Makers cut grooves along a thin board of wood and lay thin sticks of graphite in them. They glue a second board on top, then cut the wood sandwich into pencils.
