Pencil Drawing Portrait

Although Conté/Thoreau's system is widely accepted, not all manufacturers follow it; for example, Faber-Castell uses a different equivalence table in its Grip 2001 pencils: 1 = 2B, 2 = B, 2½ = HB, 3 = H, 4 = 2H.
The various graphite pencil grades are achieved by altering the proportion of graphite to clay: the more clay the harder the pencil. Two pencils of the same grade but different manufacturers will not necessarily make a mark of identical tone nor have the same hardness.