The Complete Handbook of Pencils

Chapter 1: Understanding Pencils

Pencils are among the oldest manufactured writing instruments still in continuous production, and their engineering has changed little in over a century. But "little change" is not the same as "no change". The pencil you hold is a precision assembly of several materials, each of which affects how it writes, sharpens, and lasts. Before we discuss types, selection, or maintenance, you need to understand what the object actually is and what its parts do.

The core is not lead, and the mistake has consequences. The "lead" in a pencil is a mixture of graphite, clay, and a binder. Graphite is a crystalline form of carbon, and its layered structure is what allows it to deposit a dark mark on paper: as the pencil moves, microscopic platelets of graphite shear off and adhere to the surface. Pure graphite is soft and smeary; it would crumble and make an illegible, greasy mark. Clay is the stiffening agent. Mixed in powdered form with the graphite, it acts as a binder and a hardener. The ratio of clay to graphite determines the hardness grade. A pencil marked "2H" has a higher clay-to-graphite ratio than an "HB", which means a harder core that resists wear and produces a lighter, thinner line. A "2B" has more graphite, making it softer, darker, and faster-wearing. This is the entire basis of the H/B scale that dominates the industry. The binder, typically a modified cellulose or wax, holds the mixture together before and during firing.