Ever stop and ponder the pure simple elegance of your trusty, yellow, pencil? As sketching implements go, the pencil is pretty much the be all and end all. You can make precise marks with a sharp tip, or use a blunted end to shade in a drawing. And if you mess up, not to worry, it erases! You always know how much longer the pencil will last, and just between you and me, chewing on pencils is a great stress buster.
So, how did such a perfect writing and drawing tool come to be, anyways?
The History of the Pencil
The pencil dates back to the ancient Romans, and probably even earlier. The Romans would write on papyrus with thin brushes called pencillus or “little tail”. To keep things neat and tidy, a small lead disc, called a plumbum, was used to draw guidelines.
Over time of course, this developed into thin rods of lead, and eventually, those thin rods started to get hand carved wooden casings… and Voila! The pencil was born.
In the mid 16th century, a deposit of extremely pure graphite was discovered in England. The mysterious substance was greasy and left a black mark on whatever it touched. Because of this, it was called plumbago, meaning “that which acts like lead”.
In 1779, K.W. Scheele finally discovered that graphite was, in fact, a form of carbon, and soon after this discovery its name was officially changed by A.G. Werner from plumbago to graphite.
Did You Know?
Graphite powder is an excellent ‘dry’ lubricant (it is used to loosen up stiff door locks). This is because the powder absorbs atmospheric fluids in between the graphite layers, giving the powder lubricating properties. Graphite – Beautiful Chemistry
In graphite, individual carbon atoms are bonded to three neighbors, all in a plane, all exactly 120o apart. Because of this, graphite structurally looks like sheets of honeycombs – mosaics of hexagons.
These sheets are held together by weak forces called van der Waals forces. This means that the honeycomb plains can be cleaved with relatively little effort, making graphite a brittle material that can shatter easily. It is this feature that actually helped bring graphite into the world spotlight – After graphite was first discovered, the deposit could easily be sawed into small square leads.
Did You Know?
Graphite is elemental carbon – so is diamond. In graphite, the carbon atoms are organized in sheets, whereas in diamond, they are organized in a 3D lattice. Of course, most of the graphite deposits worldwide (and there are deposits in almost every country) are not pure, and unfortunately, impure graphite is often flaky and/or lumpy and certainly doesn’t cut neatly into small square sticks…certainly not a desired feature for making pencils.
How Pencils are Made
To overcome the problems that impurities would bring to making pencils, graphite and clay are first mixed in with water, and the resulting sludge is dried, and then rehydrated into a moldable paste.
The paste is then extruded through a small metal tube and the ‘leads’ are cut into to pencil length pieces. The leads are then dried, and heated to in an oven 1000 degrees C or higher to make then smooth and hard.
Since graphite is soft, greasy and black, clay is added to yield a harder lead. The process is the same for all varieties of pencil – any of the seventeen different grades, 9H (very hard; less graphite), through the trusty old HB, to 9B (very soft; more graphite)
Did You Know?
Yellow is by far the most popular colour choice for painting pencils – a tradition that goes back to the 1800’s, when the best pencils were painted yellow Once prepared, the pencil leads are glued in between two grooved wooden slats, from which individual pencils are formed. The pencils are finished with paint then a ferrule (a small metal ring) and eraser. Finally, the pencil is stamped with letters that define its hardness and blackness and it is done. A fresh new pencil for writing, drawing, shading, erasing – or even chewing.
The General Pencil
Wikipedia on the Pencil
Wikipedia on Graphite
Ritter, Steve. Pencils and Pencil Lead. Chem Eng News. 79(42). p.35
The Pencil: A History of Design and Circumstance by Henry Petroski (1992)
General Chemistry 2nd Edition, by Petrucci/Harwood/Herring (2003)
Kate Woods is a graduate student at UBC who studies the chemistry of various marine creatures. Kate hopes for a long and healthy life, thus she makes sure to eat plenty of veggies - even tomatoes.