and HB-grade pencils fit the bill. But what do those grades mean? The letter H in the grading system designates the graphite’s hardness, the B its blackness. The degree of each attribute is ...

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 ...

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 ...

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 ...

Numbers are used to classify grades of pencils in the United States ... A No. 2 pencil is towards the middle when it comes to the hardness of lead (graphite) and the darkness of the shade.

The pencils are graded by their ratio of graphite to clay. Grades ranged from 9B to 2H, where H denotes the hardness caused by the pencil’s clay content, and B denotes the blackness due to the ...

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 ...