More information: Tomoya Kamine et al, Pencil lead etched by plasma: Novel photonic material that can control the reflection from the visible to the infrared region, Optical Materials (2024).

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 ...

The whole point of a mechanical pencil is to have perfect sharpness forever. Yet without precise engineering and build quality, the standard slender leads are doomed to constant breakages. This ...