Pencil makers in the United States often use a number scale in which higher numbers mean harder graphite, while manufacturers in other countries often use a letter scale that grades based on hardness, blackness and ability to sharpen. However, these marks vary as manufacturers employ their own grading standards.Continue Reading
Makers who use the letter scale grade harder pencils with the H designation. Softer pencils get a B for blackness. The F designation indicates that the graphite is firm enough to sharpen to a fine point.
Pencil lead is not lead at all, but rather a mixture of graphite and clay powder, the ratio of which determines the pencil's hardness. More clay in the mixture results in harder pencils that make faint marks.Learn more about Drawing