How does a lead pencil write on paper?

A pencil is usually made with a piece of carbon mixed with clay that has a wood case around it. Coloured pencils are a type of pencil that instead of grayish silver, the tip is of different colors. Coloured pencils or crayons are usually meant for drawing rather than writing.

An important difference between pens and pencils is that the tip of a pencil is made of graphite (or lead) and pens have tips made of metal with ink coming out of the bottom. Pencil writings do not smudge or wash away if the paper gets wet, unlike pens which have ink which is soluble and smudges. Writing from a pencil can be erased, but writing from a pen usually cannot. Finally, while pencils have been around for thousands of years, pens have only been around for about three hundred years.

Pencil lead is not lead at all; it's a combination of finely ground graphite and clay, mixed with water and pressed together at high temperatures into thin rods. Graphite is the Greek word meaning "to write". While writing with a pencil the particles of graphite get peeled off from the graphite rod and get deposited on the paper.

Varying amounts of clay changes the hardness of the "lead" in a pencil. The number printed on the side of the pencil indicates hardness and darkness of the graphite core: the higher the number, the harder the graphite core. Because a hard core leaves behind less of the graphite-clay mixture on the paper, it will have a fainter mark than a softer core. Pencils are used for both writing and drawing, and the result is durable; although writing can usually be removed with an eraser, it is resistant to moisture, most chemicals, ultraviolet radiation and natural aging.

Erasers eradicate pencil markings by lifting graphite particles from the paper. Erasers are mostly made from petroleum-based synthetic rubber compounds. Because the particles in the polymer that make up an eraser are stickier than paper, those graphite particles get stuck to the eraser instead, making the paper clean.