The pencil “lead” is actually a mixture of graphite and clay. More clay in the mixture makes the lead harder. A harder lead has a higher number. Pencils are numbered from 1-3 but most people use a ...

an eraser and a sharpener – you’ll never go without a pencil full o’ lead again. Each graphite lead refill is 120mm long and ...

These structural colors form due to a phenomenon known as thin-layer interference between clay and graphite, which are the ...