How is pencil lead hardness graded?


Quick Answer

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.

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Full Answer

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.

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