How are pencils made?

1. A pencil core starts as two powders: shiny black graphite and gray clay. They are mixed with water into a thick paste, like cookie dough.
2. The paste is pushed through a tiny hole, like squeezing toothpaste. It comes out as a long, thin rod that is cut into pencil-length pieces.
3. The rods are baked in a kiln, a super hot oven, until they are hard. Then they soak in wax so they glide smoothly across paper.
4. Meanwhile, soft wood, often cedar, is cut into thin, flat boards called slats. A machine cuts grooves into each slat to hold the cores.
5. A core is laid in every groove. A second grooved slat is glued on top, making a pencil sandwich that is pressed until the glue is dry.
6. Spinning cutters shape the top and bottom of the sandwich, splitting it into separate pencils. Each pencil gets several coats of paint, and often a metal band and an eraser.
7. Finally the pencil is sharpened into a cone. When you write, tiny flakes of graphite rub off and stick to the paper. That is your line!

This pencil has been cut in half the long way. Tap each part to see what it does.

• Graphite core. The core is graphite mixed with clay, baked hard. There is no lead in it at all, even though people call it pencil lead!
• Wood casing. The core sits inside two halves of soft wood glued together. The wood protects the breakable core and is easy to sharpen.
• Glue line. Look closely at the end of a pencil: you can often see a thin line where the two halves of wood were glued together.
• Paint. The pencil gets several thin coats of paint. Paint makes it smooth to hold and protects the wood.
• Metal band (ferrule). The metal band is called a ferrule. It is squeezed tight around the wood and the eraser to hold them together.
• Eraser. The eraser is soft and grabby. It picks up the graphite flakes from the paper and rolls them away in crumbs.
• Sharpened point. Sharpening cuts the wood into a cone and shows the tip of the core. A sharp point makes thin lines; it gets rounder as you write.
• Grade mark. Letters like HB show how hard the core is. H means hard and light, B means black and soft, and HB is in the middle.

Choose how much graphite and clay go into the core. Make the pencil step by step, then test it on paper and compare it with the grade chart.

Experiment: Which core makes a darker line: one with more graphite or one with more clay?

1. Slide toward more graphite and watch the core color.
2. Make the pencil and test it on the paper.
3. Compare your line with the grade chart at the top.

What we found: More graphite makes a softer core that leaves more dark flakes on the paper. More clay makes a harder core and a lighter line. Soft cores also wear down faster.

Turn on JavaScript to try it yourself.

An artist wants a dark, soft pencil for shading. An engineer wants a hard pencil for light, neat lines. Make a pencil for each of them.

The gray stuff in a pencil is graphite, a kind of carbon. Graphite is built like a stack of paper sheets. The sheets slide off each other very easily, so when you drag a pencil across paper, tiny flakes rub off and stick to the rough paper. That trail of flakes is your line.

Pure graphite would be too soft and crumbly to make a good pencil. So pencil makers mix it with clay and bake it hard. The more clay they add, the harder the core and the lighter the line. The more graphite, the softer and darker it is.

Pencils have letters to tell you how they will draw. H stands for hard, and B stands for black. An HB pencil is in the middle, which is why it is a favorite for schoolwork. Artists use soft B pencils for dark shading and hard H pencils for light sketches.

The wood around the core is soft and straight so it is easy to sharpen. Many pencils have six sides, which helps your fingers grip them and stops them from rolling off the table.

Key words

Graphite

A soft, slippery form of carbon made of sheets that slide apart easily.

Clay binder

Clay mixed into the core to make it harder.

Kiln

A very hot oven used to bake (fire) the cores until they are hard.

Extrusion

Pushing a paste through a small hole to make a long rod of the same shape.

Grade

Letters such as 2H, HB or 4B that tell you how hard or soft the core is.

Check your thinking

1. What is the writing core of a pencil mostly made of?

   Show the answer

   Graphite and clay. The core is graphite mixed with clay and baked. There is no lead in a pencil.

2. Which pencil grade draws the darkest line?

   Show the answer

   4B. B means black: 4B is soft and dark. H grades are hard and light.

3. Why are pencil cores baked in a kiln?

   Show the answer

   To make them hard and strong. Baking turns the clay hard, like a pottery mug, so the core holds together.

4. How does the core get inside the wood?

   Show the answer

   It is glued into grooves between two slats of wood. Cores are laid in grooved slats, a second slat is glued on top, and the sandwich is cut into pencils.

5. Graphite and diamond are both pure carbon. Why is graphite soft while diamond is hard?

   Show the answer

   In graphite, layers are held by weak forces; in diamond, every atom is strongly bonded in 3D. Same atoms, different structure: graphite's layers slide; diamond's network does not.