<Li> Vincent van Gogh used only Faber pencils as they were "superior to Carpenters pencils, a capital black and most agreeable". </Li> <Li> Johnny Carson regularly played with pencils at his Tonight Show desk . These pencils were specially made with erasers at both ends to avoid on - set accidents . </Li> <Li> Roald Dahl used only pencils with yellow casing to write his books . He had 6 sharpened pencils ready at the beginning of each day and only when all 6 pencils became unusable did he resharpen them . </Li> <Dl> <Dt> Graphite pencils </Dt> <Dd> These are the most common types of pencil, and are encased in wood . They are made of a mixture of clay and graphite and their darkness varies from light grey to black . Their composition allows for the smoothest strokes . </Dd> <Dt> Solid graphite pencils </Dt> <Dd> These are solid sticks of graphite and clay composite (as found in a' graphite pencil'), about the diameter of a common pencil, which have no casing other than a wrapper or label . They are often called "woodless" pencils . They are used primarily for art purposes as the lack of casing allows for covering larger spaces more easily, creating different effects, and providing greater economy as the entirety of the pencil is used . They are available in the same darkness range as wood - encased graphite pencils . </Dd> <Dt> Liquid graphite pencils </Dt> <Dd> These are pencils that write like pens . The technology was first invented in 1955 by Scripto and Parker Pens . Scripto's liquid graphite formula came out about three months before Parker's liquid lead formula . To avoid a lengthy patent fight the two companies agreed to share their formulas . </Dd> <Dt> Charcoal pencils </Dt> <Dd> Are made of charcoal and provide fuller blacks than graphite pencils, but tend to smudge easily and are more abrasive than graphite . Sepia - toned and white pencils are also available for duotone techniques . </Dd> <Dt> Carbon pencils </Dt> <Dd> They generally are made of a mixture of clay and lamp black, but are sometimes blended with charcoal or graphite depending on the darkness and manufacturer . They produce a fuller black than graphite pencils, but are smoother than charcoal . </Dd> <Dt> Coloured pencils, or pencil crayons </Dt> <Dd> These have wax - like cores with pigment and other fillers . Multiple colours are often blended together . </Dd> <Dt> Grease pencils </Dt> <Dd> They write on virtually any surface (including glass, plastic, metal and photographs). The most commonly found grease pencils are encased in paper (Berol and Sanford Peel - off), but they can also be encased in wood (Staedtler Omnichrom). </Dd> <Dt> Watercolour pencils </Dt> <Dd> These are designed for use with watercolour techniques . The pencils can be used by themselves for sharp, bold lines . Strokes made by the pencil can also be saturated with water and spread with brushes . </Dd> </Dl>

When did they take lead out of pencils