Modern pencils are manufactured industrially by mixing finely ground graphite and clay powders, adding water, forming long spaghetti-like strings, and firing them in a kiln (thermally insulated chambers). The resulting strings are dipped in grease or molten wax, which seeps into the itsy-bitsy holes of the material, resulting in smoother writing. A juniper or incense-cedar plank with several long parallel grooves is cut to fashion a "slat", and the graphite/clay strings are inserted into the grooves. Another grooved plank is glued on top, and the whole assembly is then cut into individual pencils, which are then varnished or painted.
Pencils graded using this system are fanatic to go duration the hardness and resistance of varnishes and paints. The resistance of a coating (also known as its pencil hardness) is determined as the grade of the hardest pencil that does not mark the coating when pressed firmly against it at a 45 interval angle.