Ceramic Coating & PPF Guide: Understand
What 8H, 9H and 10H Mean on a Ceramic Coating
Almost every ceramic coating ad leads with a number followed by H. 9H is common, 10H is the premium badge, and some budget products claim the same numbers as professional ones. It is easy to assume the number means the paint can no longer be scratched, or that a 10H coating is twice as tough as a 5H one.
Neither is true. The H rating comes from a simple, old test borrowed from the paint industry, and it measures one narrow thing. Here is what that test does, what it predicts and what it leaves out.
The short answer
8H, 9H and 10H are pencil hardness ratings. In the test, pencil leads of increasing hardness are pushed across a cured coating, and the rating is the hardest pencil that does not scratch or gouge it. A higher number means a harder surface film under those test conditions. It is a rough ranking tool, not a measure of rock chip, impact or deep scratch resistance, and results vary by lab and test panel.
Key points
- The H scale comes from graphite pencil grades; it is not the Mohs mineral scale.
- The industry method (ASTM D3363) is quick and cheap, and its own scope warns about variation between labs and pencils.
- A coating tested on a hard panel scores higher than the same coating would on a softer base.
- Hardness helps a coating resist light marring; it does nothing for impacts like rock chips.
- Durability depends more on film thickness, chemistry, prep and care than on the H number alone.
The test
How the pencil hardness test works
The standard method in North America is ASTM D3363, Film Hardness by Pencil Test. ASTM describes it as a quick, inexpensive way to judge the hardness of an organic coating on a metal or similarly hard substrate, using drawing leads of known hardness.
The idea is simple. A pencil lead, prepared to a standard tip, is pushed across the cured film with steady force at a fixed angle. If it cuts or scratches the coating, the tester steps down to a softer lead and tries again, until one leaves the film intact. IGL describes running the test with half-inch lines and repeating it to confirm the result.
The rating is that last pencil grade. A coating that survives a 9H lead but not a 10H lead is rated 9H. A coating that a 10H lead will not mark is rated 10H, which is why 10H is effectively the top of the scale for coatings.
The scale
From soft B to hard H
Pencil grades run from very soft, dark B leads, through HB and F in the middle, up to the hard H grades. The higher the number after H, the harder the lead and the lighter the line it leaves. IGL notes that a 10H lead leaves the least graphite because it is the hardest.
The scale is ordinal, not proportional. Each step is harder than the last, but 10H is not twice as hard as 5H, and the jump from 9H to 10H is not a fixed amount. That is one reason ASTM says the method is useful for ranking coatings with clearly different hardness and calls for caution when comparing coatings that are close.
- Not the Mohs scale
- Mohs ranks minerals by which one scratches another. IGL points out that graphite pencils only rate about 1 to 2 on Mohs, and that mineral scales are not well suited to coatings. A 9H coating is not "9 on the Mohs scale" no matter how an ad phrases it.
Variables
Why the same coating can score differently
The test has known weak spots, and the standard says so. ASTM notes that results can vary between laboratories, especially when different pencil manufacturers or substrates are used, and that even different production batches of pencils can shift results within the same grade.
The test panel matters most. ASTM limits the method to coatings on metal or similarly hard substrates, because on a softer base the result reflects the base deforming more than the coating's hardness. IGL makes the same point from the other direction: a coating applied on a hard base will naturally test harder. IGL says its tests typically use films about 25 to 38 microns thick, cured for 7 days.
Your car's coating sits on clear coat, which sits on base coat, primer and metal or plastic. That stack is softer and more flexible than a lab steel panel or glass slide, so the rating describes the coating's potential, not exactly how your hood will behave.
- Pencil brand and batch
- Lead preparation and tip shape
- Force and angle (fixed rigs help; hand tests vary)
- Test panel material and film thickness
- Cure time and temperature before testing
Predicts
What a higher H rating does tell you
A harder cured film generally resists fine marring better. Light wash marks, a towel dragged with a little grit, or a gentle brush against the paint are more likely to mark a soft film than a hard one. That is where hardness earns its place on a spec sheet.
Hardness is also a sign of cure. ASTM notes the test is used to check how well heat-cured coatings have cured, and coating makers use it the same way: a coating that reaches its rated hardness has crosslinked as intended.
Within one manufacturer's range, a higher rating usually tracks a more concentrated, thicker-building product. IGL rates its EZ coating at 8H, Quartz+ at 9H and Kenzo at 10H, and the three are also sold at different durability levels. The hardness number is one clue to that ladder, not the cause of it.
Doesn't predict
What the H number leaves out
The pencil test is a scratch test with a slow, steady load. A rock chip is an impact: a small stone hitting the front of the car at highway speed, often from a truck tire on I-85 or a gravel road shoulder. Impact resistance depends on how a material absorbs and spreads energy, and a thin hard film over paint has almost no room to do that. This is why thick, flexible urethane film, not a harder coating, is the answer for chips.
Deep scratches are another limit. Keys, sand trapped in a brush wash or a fingernail-catching scratch cut through the coating and into the clear coat below, regardless of rating. IGL itself says the pencil test is only one of many tests used to evaluate coatings, that you should not judge a finish entirely on hardness, and that a coating strong in one property, such as UV resistance, may not match another in heat or abrasion resistance.
- For chips, look at film
- Paint protection film is a thick, self-healing urethane layer built to absorb impacts that no coating can stop. Ceramic coating vs PPF
- Other limits
- Dings, water spots and washing are covered in a plain list of what a coating will not do. What a coating won't do
Shopping
How to read a hardness claim
Look for the test method
A rating with a named method such as ASTM D3363, and ideally the panel and film thickness, means more than a bare "9H" on a label.
Compare within one brand
Ratings from different companies, labs and pencil sets are not directly comparable. A brand's own ladder (8H, 9H, 10H) is more meaningful than a cross-brand comparison.
Weigh durability and chemistry
Rated years, layers, solids content and the technical data sheet's care instructions tell you more about real life than hardness does.
Ask about prep
A 10H coating over swirled, contaminated paint performs worse than a 9H coating over corrected, clean paint. Prep decides the result.
Be wary of extreme claims
Numbers above the scale ("12H", "20H") or claims that a coating stops chips or scratches are marketing, not test results.
| Rating | Test result | Real-world meaning | Example |
|---|---|---|---|
| 8H | An 8H lead does not mark the film; a 9H lead does | Good resistance to fine marring for an entry coating | IGL EZ |
| 9H | A 9H lead does not mark the film; a 10H lead does | Harder film; common rating for professional coatings | IGL Quartz+ |
| 10H | Even a 10H lead does not mark the film | Top of the pencil scale; still no protection from impacts | IGL Kenzo |
None of these ratings means the coating resists rock chips, dings or deep scratches.
Choose a coating by how you drive, not by the H
We install IGL EZ (8H), Quartz+ (9H) and Kenzo (10H). At inspection we will help you match durability to how you wash and park, and tell you where film makes more sense.
Common questions
Is a 10H coating better than a 9H coating?
It is harder in the pencil test, which can mean slightly better resistance to fine marring. Whether it is better for you depends on durability, layers, prep and how you care for the car. Within one brand, the 10H product is usually the more concentrated, longer-rated coating, but the hardness number alone does not decide that.
Is 9H the hardness of the coating or the hardness of my paint?
It describes the coating film as tested on a hard panel. Your clear coat is a separate, softer layer, and the coating is very thin, so under a heavy load the paint below can still deform or scratch. Think of the rating as the coating's surface hardness under lab conditions, not a new hardness for your whole paint system.
Why do cheap coatings also claim 9H?
Because the test is simple and the number is easy to print. Results vary with pencil brand, panel material and film thickness, and there is no independent body checking label claims. A low-priced product can reach 9H on a glass slide and still be thin, short-lived or hard to apply well. Look at the technical data sheet, rated durability and the installer's prep instead.
Can a ceramic coating be scratched with a fingernail?
A fingernail is far softer than a cured coating, so it will not cut a properly cured film. What it can do is drag grit across the surface, and the grit can leave marks. Fingernails are also a good tool for judging scratch depth: if a scratch catches your nail, it usually goes through the clear coat, and no coating will hide it.
Sources
- ASTM D3363-22, Standard Test Method for Film Hardness by Pencil Test, ASTM International (https://store.astm.org/d3363-22.html), accessed October 2026
- Ceramic Coating Hardness, IGL Coatings blog (https://blog.iglcoatings.com/ceramic-coating-hardness/), accessed October 2026
- Difference Between 10H and 9H Ceramic Coating, IGL Coatings blog (https://blog.iglcoatings.com/difference-between-10h-and-9h-ceramic-coating/), accessed October 2026
- Ecocoat Kenzo, IGL Coatings (https://iglcoatings.com/products/ecocoat-kenzo-graphene-reinforced/), accessed October 2026
- Ecocoat Quartz+, IGL Coatings (https://iglcoatings.com/products/ecocoat-quartz-plus/), accessed October 2026
Prices on this page are The Auto Show’s published starting prices and are confirmed after we inspect the vehicle. Product ratings and warranty terms come from the manufacturers.