A pencil's hardness is indicated by a range of numbers and letters-"H" for hardness and "B" for blackness-with 9H producing the lightest strokes and 9B the darkest. A higher proportion of graphite produces harder, more silvery tones, whereas a greater amount of clay yields softer and blacker pencils. Today's pencils are remarkably similar to Conté's original recipe and design, in which the mixture is extruded into long rods (commonly referred to as "leads"), fired, and encased in wood sheaths.Īdjusting the proportions of graphite and clay produces variations in both texture and depth of tone. By the by end of the eighteenth century, pencils (a word derived from the Latin peniculus for brush) would be fabricated from clay and low-quality graphite, based on the invention of Nicolas-Jacques Conté (1755–1805). The mines at Borrowdale were eventually depleted, provoking a search for a substitute. Well suited for drawing, this soft, high-quality material was cut into sticks and either wrapped with twine for grasping between the fingers or placed in a porte-crayon, a tool designed to hold a small piece of chalk or charcoal. The purest graphite originated in the northern English valley of Borrowdale. Graphite was used for drawing in Central Europe during the sixteenth century, but its use became more widespread in the late eighteenth century. This surface quality helps to distinguish graphite drawings from works in black chalk. Composed of disk-like particles that readily slide over one another, graphite easily produces marks on paper or vellum that often appear shiny when viewed in obliquely-angled or raking light. The mineral graphite is a crystalline form of the element carbon, which occurs naturally in various types of rocks. Clockwise from upper center: mineral graphite, range of modern pencils, variety of erasers, sharpener, knives, stumps, various types of porte-crayons (holders)
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