For writing, choose pencils with F, HB, B, 2B, or 3B leads. As the B increases, the lead becomes softer and the writing darker. As the H increases, the lead becomes harder and the writing lighter.
Coal: They are mainly used in painting, as they achieve a deeper black. They smudge more than graphite pencils. They require a special eraser for erasing.
Graphite: Ideal for all uses, especially for writing and drawing.