9H (Pencil Hardness)
Quick answer: “9H” is a result from the pencil hardness scratch test on coatings. It means the cured film resists being cut by a 9H graphite pencil under a specified load and angle. It is not the Mohs scale and does not mean scratch-proof paint.
What it means
The pencil hardness test (often ASTM D3363 or JIS K5600-5-4) uses graded pencils from softer (B) to harder (H, up to 9H). The highest-numbered hard pencil that does not cut or gouge the coating defines its rating. A “9H ceramic” claim therefore describes resistance to that particular lab method on a flat test panel after proper cure.
Why it matters
- Indicates comparative scratch and mar resistance of a cured coating film under controlled conditions.
- Helps compare coatings and clear coats when tested the same way with the same load and technique.
- Sets realistic expectations: higher pencil hardness can reduce fine marring but will not stop all scratches.
Where you’ll see it
On ceramic coating datasheets and marketing claims such as “9H hardness” for paint, glass and phone-screen coatings.
Context
Car Paint Protection; Ceramic coatings
Common mistakes
- Confusing pencil hardness with Mohs hardness – 9H pencil is not “hardness 9 on Mohs” and does not equal sapphire or diamond.
- Assuming “9H” means scratch-proof – it only reflects resistance to a specific pencil test, not keys, grit or wash abuse.
- Comparing results from different labs without matching test load, angle, substrate, cure time and environment.
- Forgetting the test is done on flat panels – curved automotive panels, contamination and real-world washing are harsher.
Written by Danny Argent. Last updated 06/11/2025 17:27