<P> A pencil is a writing implement or art medium constructed of a narrow, solid pigment core inside a protective casing which prevents the core from being broken and / or from leaving marks on the user's hand during use . </P> <P> Pencils create marks by physical abrasion, leaving behind a trail of solid core material that adheres to a sheet of paper or other surface . They are distinct from pens, which instead disperse a trail of liquid or gel ink that stains the light colour of the paper by absorption . </P>

When did they start putting graphite in pencils