Before Conté, pencil hardness varied from location to location ... using a combination of numbers and letters known as the HB Graphite Scale. So why are testing centers such sticklers about ...

That number two rating is based on a scale for hardness: 1 ... David Thoreau when he was working at his family's pencil factory. American graphite was inferior to English graphite, and to separate ...

Pencils are labeled based on graphite hardness, which in turn affects the ... and shade and are ideal for everyday use. The numeric scale is used by pencil manufacturers in the United States ...

While we number our various grades of pencils in the U.S ... the Thoreaus were selling pencils with varying graphite hardness, which they numbered one through four. According to most stories ...

Creating different hardness' to pencils was discovered by Nicholas Jacques Conté. Mixing powdered graphite with clay and forming the mixture into rods that were then fired in a kiln. By varying ...