Indicators on Sketching Pencils You Should Know

^ Pencil grades fluctuate "dependent on the producer, once the pencils are made, and the source of graphite and clay. 1 analyst identified that graphitic carbon content, by way of example, to vary from about 30 to about sixty five in many different different pencils bearing a similar designation." Petroski 1990, p. 229 ^ This is not connected with

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