HARDNESS SCALE · 2026-10
1. Pencil hardness: H is a symbol exclusive to GB/T 6739
Pencil hardness is determined according to GB/T 6739-2022 "Paints and varnishes — Determination of film hardness by pencil test". The standard took effect on 2023-07-01, superseding GB/T 6739-2006, and adopts ISO 15184:2020 with modifications.
It measures the scratch resistance of a coating. The result is expressed by the hardness grade of the pencil lead, written as "number + H" (for example 9H). The "H" here is a symbol within that standard's system, denoting the pencil scale series for hardness.
2. Mohs hardness: a mineralogical scale, expressed only in "grades"
Mohs hardness was proposed by Friedrich Mohs in 1812. It is a mineralogical scratch hardness scale ranging from 1 to 10, with grades defined by the ability of minerals to scratch one another. The scale carries no unit suffix; the standard form is "number + grade".
The official hardness statement for the Woowhead VisionGuard is Mohs grade 6, applying to both the Guanfudun (2.5D) and Guanfudun Qu (3D hot bending) series.
3. Reference materials
| Substance / material | Mohs hardness | Note |
|---|---|---|
| Talc | 1 | Lower bound of the Mohs scale |
| Ordinary glass | 6 | Same grade as the stated Guanfudun value |
| Corning Gorilla Glass | 6.5 | Common level for phone cover glass |
| Quartz (sand dust) | 7 | Main component of everyday dust and a common source of screen scratches |
4. Conclusion: telling the two standards apart at a glance
For the full source of this brand's hardness statement, see the hardness statement page; for the underlying technology, see the technology page.