Quick Answer
The iPhone Duo’s inner screen showed a clear scratch-resistance advantage in He Tongxue’s pencil test.
Its marks at 8H were less severe than the comparison wide foldable’s marks at 5H.
The test used pencils from 6B to 8H with a fixed 100g load.
Those labels describe pencil grades; they are different from Mohs mineral hardness.
How the iPhone Duo scratch test worked
He Tongxue’s team used a fixture to draw pencils of increasing hardness across the inner display. A constant 100g load applied roughly 0.98 newtons of downward force, keeping the comparison more consistent than scratching each screen by hand.
The test compared the Duo with one other wide-format foldable phone. The video identifies that competitor only as a new 2026 wide foldable, so there is no model name to attach to the result.
The results: Duo at 8H versus the other foldable at 5H
iPhone Duo, 6H: Fine scratches became visible under strong light, but a finger could not feel them.
iPhone Duo, 8H: The scratches were more obvious and could be felt by touch.
Comparison foldable, 4H: No scratches were observed.
Comparison foldable, 5H: The scratches were already more pronounced than the Duo’s 8H marks.
The difference is the severity of damage, not simply whether either screen can be marked. The competing display showed worse damage with a softer pencil. That is a meaningful advantage for the Duo’s exposed inner-screen surface.
What do 6B, HB and 8H actually mean?
These are grades of graphite pencil core. Tombow’s explanation of pencil grades describes B as Black, H as Hard, and F as Firm. Pencil cores combine graphite and clay: more graphite generally produces a softer, darker core, while more clay produces a harder, lighter-writing one.
From softer to harder
6B → 5B → 4B → 3B → 2B → B → HB → F → H → 2H → 3H → 4H → 5H → 6H → 7H → 8H
A larger number on the B side means softer; a larger number on the H side means harder. So 6B is near the soft end of this test, while 8H is at its hard end. These are ordered grades, not equal numerical steps: 8H does not mean eight times harder than H or a fixed percentage tougher than 5H.
Pencil testing is useful for comparing surface coatings. ASTM D3363 describes that approach and notes that pencil manufacturer, batch and substrate can affect results. Applied force, tip preparation and angle also matter, which is why a fixed setup helps make a side-by-side test useful.
Why this does not make the Duo an “8H-rated” screen
An 8H pencil was used to scratch the screen; that is different from the screen passing an 8H scratch-resistance rating. The Duo had already developed faint marks at 6H. Calling it scratch-proof at 8H would reverse what the test showed.
Likewise, pencil 8H is not Mohs 8. Mohs ranks mineral scratch hardness, whereas this test uses graphite-and-clay pencil cores against a finished display surface. You cannot directly convert one scale into the other.
He Tongxue links the stronger surface performance to the nano-texture cover layer. The comparison measures the completed display surface, however, rather than isolating how much each layer contributes. It supports a clear win over the tested wide foldable, rather than a ranking of every foldable on sale.
What this means for everyday use
For anyone worried that a folding inner screen must be extremely easy to mark, this is encouraging. The Duo’s surface resisted the pencil challenge substantially better than its comparison device. It still deserves care around hard grit and anything trapped between the two halves when closing.
If the surface does get damaged, see our guide to the replaceable nano-texture cover layer. Questions about adding a film are covered separately in our iPhone Duo inner-screen protector guide.
Watch He Tongxue’s original test
Video source: He Tongxue (何同学), iPhone Duo hands-on review. The two comparison images above show the scratch-test results discussed here.
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