Pencils are numbered (or lettered and numbered) to indicate the hardness of the graphite lead within them.
Historically, the hardness of pencil leads has been described using the HB system, which uses the letters "H" for hardness, "B" for blackness, and "HB" for pencils that fall in the middle of the scale. Now, pencils often display a number alongside these letters to provide a more granular indication of hardness.
Here's a breakdown:
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H (Hardness): Pencils marked with an "H" contain more clay and less graphite, resulting in a lighter, finer line. Higher numbers (e.g., 2H, 4H, 6H) indicate progressively harder leads. These are good for technical drawings and detailed work.
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B (Blackness): Pencils marked with a "B" contain more graphite and less clay, resulting in a darker, broader line. Higher numbers (e.g., 2B, 4B, 6B) indicate progressively softer and darker leads. These are preferred for sketching and shading.
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HB: HB pencils fall in the middle ground, offering a balance between hardness and blackness, making them suitable for general writing and drawing. A #2 pencil is generally equivalent to HB.
Number and Letter Examples:
| Pencil Marking | Hardness/Darkness | Typical Use |
|---|---|---|
| 9H - 4H | Very Hard, Very Light | Technical drawing, architectural drafting |
| 3H - H | Hard, Light | Light sketching, precise lines |
| F | Firm (close to HB) | General Writing |
| HB (#2) | Medium | Writing, general drawing |
| B - 6B | Soft, Dark | Sketching, shading |
| 7B - 9B | Very Soft, Very Dark | Artistic drawing, expressive lines |
So, a 4B pencil is softer and creates a darker line than a 2B pencil, and a 3H pencil is harder than an H pencil. The numbering system allows for more precise control over the darkness and fineness of the lines produced.
