What is the hardest ceramic coating?

We honestly couldn't tell you. We haven't tried all the ceramic coatings, and even if we had, we don't test them for hardness. 

While this is a valid question, it is really too narrow in focus to provide much meaning. The ceramic coating its self is strong rather than hard. When applied to your paintwork, it makes the paint harder, and this is tested using Wolff-Wilborn Test, colloquially called the Pencil Test. Any ceramic coated paint tested on the Wolff-Wilborn scale is H9, which is as high as the scale goes.

Although not officially part of the Wolff-Wilborn scale, Koh-i-noor testing pencil sets do include a 10H. Some brands of ceramic coatings are now claiming to be 10, but this should be treated with some scepticism for two reasons, firstly 10h is not part of any official standard and is incompatible with ISO 15184, secondly, other brands would probably only been tested with a set that goes up to 9H, so may be just as hard. 

(For what it's worth, I am a huge fan of Koh-i-noor, and I own a number of their mechanical pencils, but their Kolinsky Brushes are very disappointing!)

So, rated on hardness, they are all pretty much the same which is to be expected which you consider that they are all a coating of silica dioxide and resins. It is also the case that ceramic coatings are no longer a new technology, and there is unlikely to be any significant technological developments which will leapfrog one ceramic coating ahead of all the others in this respect.

However, they aren't all the same. Most of the differences are in things like ease of application, which doesn't impact the end result (although they may impact the price).

We are now seeing diamond coatings, graphene coatings and other new products, which might not be any harder, in fact they may be softer, but might be more flexible and resistant to scratches via elasticity.

It is probably fair to say that the future could be in softer products, not harder ones.

What this question is really about

When people ask what the hardest ceramic coating is, they are usually looking for maximum protection and durability. In reality, the question is driven by published hardness numbers rather than how coatings actually behave on a car.

Why “hardness” is often misunderstood

• Most quoted hardness figures (such as 9H) come from pencil hardness tests, not real-world use
• Pencil hardness measures resistance to a stylus, not scratches from washing, grit, or road debris
• Different brands test in different ways, making comparisons unreliable

What hardness does - and doesn’t - tell you

Hardness can indicate how resistant a coating is to light marking, but it is only one small part of performance.

• It does not mean the coating is scratch-proof
• It does not prevent stone chips or impact damage
• It does not guarantee longer lifespan on the road

What matters more than headline hardness

• Surface preparation and correction quality before application
• Coating chemistry and how it bonds to the clear coat
• Thickness consistency and curing conditions
• Maintenance, washing technique, and mileage

Written by Danny Argent. Last updated 05/01/2026 18:11