Aug 2, 2013

Why Number 2 pencils

Pencil makers manufacture No. 1, 2, 2½, 3, and 4 pencils, and sometimes other intermediate numbers. The higher the number, the harder the lead and lighter the markings. Number 1 pencils produce darker markings, which are sometimes preferred by people working in publishing.

The current style of production is profiled after pencils developed in 1794 by Nicolas-Jacques Conté. Before Conté, pencil hardness varied from location to location and maker to maker. Earliest pencils were made by filling a wood shaft with raw graphite.

Conté’s method involved mixing powdered graphite with finely ground clay, shaped into a long cylinder and then baked in an oven. The proportion of clay versus graphite added to a mixture determines the hardness of the lead. Although the method is usually the same, the way companies categorize and label pencils isn't.

Today, many U.S. companies use a numbering system for general-purpose, writing pencils that specifies how hard the lead is. For graphic and artist pencils and for companies outside the U.S., systems use a combination of numbers and letters known as the HB Graphite Scale.

Testing centers prefer Number 2 pencils, because their machines use the electrical conductivity of the lead to read the pencil marks. Early scanning-and-scoring machines couldn't detect marks made by harder pencils, so No. 3 and No. 4 pencils usually resulted in erroneous results and softer pencils like No. 1 smudge. Because of this and general wide acceptance, No. 2 pencils became the industry standard.