Pencils have two graphite grading scales that are used to measure the hardness of a pencil's graphite core. First one is Numerical graphite scale, is a numerical scale which shows hardness and lightness of the writing core according to numbers, and the second one is HB graphite scale, where H letter indicates a hard pencil and B letter indicates the blackness of the pencil. #nojoto #nojotoart #basicsofart #art #pencil #pencilstrokes