The base materials of Black Conte' pencils are clays and finely ground carbon or lamp-black. These are mixed with water, sifted and filtered and then are mixed with plastifying substances to arrive at a paste, the composition of which determines the quality and graduation. Square or round leads are then obtained as required from this paste by extrusion. The leads are first dried naturally, then in drying tunnels and afterwards baked in ovens. This baking is essential, for the various graduations of leads produced deend upon the time and method of baking. The result of this 'personalised' manufacture is that for each type of pencil, there corresponds an extensive range of possibilities, characteristics, but different, according to whether a PIERRE NOIRE pencil, a CARBON pencil or a CHARCOAL pencil is used.