Why 9H Hardness Doesn't Mean What You Think

What Does 9H Hardness Actually Mean?

When a ceramic coating manufacturer says "9H hardness," they mean the pencil hardness scale. This is different from the Mohs scale, which measures minerals like diamonds and quartz.

The pencil hardness test uses graphite pencils of different hardness levels, from soft (6B) to hard (9H).

It pulls the pencils over a cured coating at a 45-degree angle using controlled pressure. If the coating resists visible scratching from a 9H pencil, it earns the 9H rating.

Most buyers don’t know the test was made for coatings on industrial surfaces, like metal panels and machinery, not for automotive clear coats.

"Pencil hardness measurements have been used by the coatings industry for many years to determine the hardness of clear and pigmented organic coating films." IGL Coatings USA

The test helps compare coatings in a lab. However, it doesn’t show how your car will resist shopping cart dings, automatic car washes, or a kid's bike handlebar.

Why the Pencil Hardness Scale Confuses Most Car Owners

Many people get confused. They hear "9H" and think it refers to the Mohs scale, which rates mineral hardness.

On the Mohs scale, a 9 is corundum (sapphire), which is harder than almost everything except diamond. So when you hear "9H ceramic coating," your brain thinks, "My car is now nearly as hard as sapphire!"

That's not what's happening.​

A 9H pencil hardness rating is nowhere near a 9 on the Mohs scale. In fact, a ceramic coating with a 9H pencil rating has a Mohs hardness closer to a 3 or 4, roughly the same as window glass.

For context, a fingernail is about 2 on the Mohs scale, and a penny is around 3.

Your ceramic coating doesn't create an impenetrable shield. Instead, it adds a thin sacrificial layer that offers moderate scratch resistance.

This gap between the rating's meaning and buyers' beliefs causes much frustration and broken trust. 

The Mohs Scale vs. Pencil Hardness: Understanding the Critical Difference

To understand why 9H hardness doesn't mean scratch-proof, you should look at the two scales:

• Mohs Scale: Rates how hard minerals are by seeing which can scratch others. A diamond (10) scratches everything below it; corundum (9) scratches topaz (8), and so on.

• Pencil Hardness Scale: This scale measures how well a coating resists scratches. It uses standardized graphite pencils for testing. It is a comparison used in industrial coating applications.

A 9H ceramic coating is rated on the pencil scale. Some manufacturers, such as IGL Coatings, offer coatings rated at 10H. This means they can resist scratches made by a 10H pencil.

The difference between 9H and 10H on the pencil scale is small. It won't greatly affect how well your car is protected from real-world hazards.

The pencil test measures how hard the coating is after it cures on a flat test surface. It doesn’t consider how the coating flexes with your car’s paint.

It also ignores how it withstands heat cycling or how it performs after six months of road grime and UV exposure.

"How a coating performs in lab tests is one thing. How it performs in the real world is the real test."

What 9H Hardness Will NOT Protect Your Car From

This is the section most ceramic coating companies don't want you to read, but it's the most important one if you want to set realistic expectations.

A 9H-rated ceramic coating will not protect your car from:

• Deep scratches or key marks: The coating is only a few microns thick, thinner than a human hair. A deliberate scratch with a key or a sharp object will go straight through the coating and into your clear coat.

• Rock chips: Ceramic coatings do not absorb impact. A rock flying at highway speed will chip your paint just as easily with or without a coating.

• Swirl marks from improper washing: Dirty sponges or harsh brushes can cause micro-scratches and swirls. This can happen whether you wash by hand or use an automatic car wash.

• Hard water spots and etching: Ceramic coatings repel water, but they're not safe from water spot etching. This is especially true if mineral-rich water dries in the sun.

"Water beading looks cool but can leave water spots if droplets dry on your paint" Water Beading Vs Sheeting

Ceramic Pro is a leading brand in the industry. They say their 9H coating acts as a sacrificial layer. This means it protects your paint by taking the damage. However, it can still get scratched or harmed.

Why Ceramic Coating Companies Use 9H as a Marketing Tool

Let's be honest: "9H hardness" sounds impressive. It's a number. It's specific. It feels scientific. In an industry with confused consumers, a clear claim like "9H hardness" gives buyers something solid to trust.

The 9H rating is now more of a marketing tool than a true measure of performance. Most ceramic coating brands, like IGL Coatings and Ceramic Pro, claim 9H or 10H hardness. This is what consumers want.

The problem is that hardness is only one variable in a coating's performance. Coatings undergo tests for various properties.

These tests check for:

• Chemical resistance
• UV stability
• Hydrophobicity
• Flexibility
• Adhesion
• Durability over time

A coating might have a 10H rating, but it can still fail in chemical resistance. It may crack after a year if it's too brittle.

[Insert real-world experience, opinion, or example here.]

Dr. Beasley argues that flexibility is more important than hardness for lasting durability. Their Nano-Resin Pro coating gives up some hardness for flexible elastomeric benefits. This lets the coating move with the paint as your car's panels expand and contract with temperature changes.

"Hardness doesn’t make a ceramic coating mar-proof, and it also isn’t the best measure of coating’s performance. Flexibility is much more significant, as it promotes better durability, longevity, and even self-healing properties." Your Ceramic Coating Should Be Flexible, Not Hard Dr. Beasley's

The Real-World Performance Issues With Ultra-Hard Coatings

Here's something many buyers overlook: ultra-hard coatings can be a risk.

Excessively hard coatings are inflexible and brittle.

Your car's clear coat isn't fixed. It moves as the steel panels beneath it expand and contract. This happens with heat, speed, and changes in the environment. If the ceramic coating bonded to that clear coat is too rigid, it can't flex with the substrate.

Over time, this can lead to micro-cracking, separation, or even delaminate.​

A flexible coating bends with the movement beneath it. It's more durable, longer-lasting, and in some cases, even self-healing.

Dr. Beasley's Nano-Resin Pro uses elastomeric polymers. These polymers compress when scratched, not break. So, minor scratches can "heal" as they return to their original form.

IGL Coatings also acknowledges this nuance. They provide 10H-rated coatings like Kenzo. But, they stress that hardness is just one part of their testing.

Other factors that are tested:

• Abrasion resistance
• Impact resistance
• Chemical resistance
• Oxidation
• Gloss
• UV resistance
• And more

What Actually Matters More Than Hardness Ratings

So if 9H hardness isn't the magic metric, what should you focus on?

Here's what really decides if a ceramic coating will meet your needs:​

• Flexibility and elasticity: Coatings that move with your paint last longer. They’re also less likely to crack or separate.

• Chemical resistance: Your car faces road salt, bird droppings, bug splatter, and tree sap. A coating's ability to resist chemical etching is just as important as hardness.

• Hydrophobic and self-cleaning: IGL Kenzo has a 120° contact angle. This makes water bead up and roll off, taking dirt along with it.

• UV Resistance: Coatings that resist yellowing, oxidation, and UV damage help your car stay looking new for years.

• Professional application vs. DIY: Even the best coating will fail if it's applied incorrectly. Surface prep, weather, and curing time are all important. - Read more about DIY coatings in this article

How to Evaluate Ceramic Coatings Beyond the 9H Claim

When you're comparing ceramic coatings, here's what to ask your installer or research on your own:

• What is the coating's full testing profile? Don't just ask about hardness. Ask about abrasion resistance, impact testing, chemical resistance, and UV stability.

• What is the coating's flexibility rating? If a brand emphasizes ultra-hardness but doesn't mention flexibility, that's a red flag.

• What is the guarantee, and what does it actually cover? Guarantees vary wildly. Some cover only coating failure, not scratches or damage.

• What kind of maintenance is required? Even the best coatings need regular maintenance washes to stay effective.

[Insert how your company approaches this challenge or service offering.]

Should You Still Choose a Ceramic Coating With These Limitations?

Yes, but only if you go in with realistic expectations.

Ceramic coatings are not scratch-proof force fields. They are sacrificial layers. They provide strong water repellency, UV protection, and resistance to chemicals.

They make your car easier to clean, keep it looking glossy, and extend the life of your paint. Brands like IGL Coatings, Ceramic Pro, and Dr. Beasley's offer great products. When applied properly, they perform well.

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But if you're expecting 9H hardness to mean your car will never scratch again, you'll be disappointed. The value of a ceramic coating lies in its full range of protective features, not just one pencil test rating.

To get honest answers about the right ceramic coating for your car, talk to a shop that’s ready to discuss your needs. Consider your driving habits and budget, too.

Ready to protect your car the right way? Schedule a discovery call with us today. We'll explain what to expect. No hype, no inflated claims. Just the truth about what ceramic coatings can and can't do for your vehicle.