a popular modern technique is the use of a charcoal stick, prepared from special vines, and a rougher form of paper. the charcoal adheres loosely to the paper, allowing very easy erasure, but the final drawing can be preserved using a spray-on "fixative" to keep the charcoal from rubbing off. harder compressed charcoal can produce a more deliberate and precise effect, and graduated tones can be produced by smudging with the fingers or with a cylindrical paper tool called a stump.