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What does ceramic coating 9H mean?

March 27, 2016 William Russell

Is 9H hardness an important factor in choosing a ceramic coating?

9H hardness is a rating on the Pencil Hardness Test, commonly used by manufacturers of clear and pigmented surface coatings.  The Pencil Hardness test is used to determine the scratch resistance of a coating surface by using pencils to scratch the surface and rate the scratch resistance in relation to that pencils hardness and other materials of similar hardness.  But is the hardness the only factor in scratch resistance?

Is the Pencil Hardness Test standardized

There are two different standards used in the pencil hardness test: ASTM D3363 and JIS K-5600-5-4.  Both require a different set of procedures and initial surface for coating to be applied to. This will allow various coatings, cured at different heats, to be tested without any other variables interfering.

The downfall with Pencil Hardness Test

The biggest concern with this testing method is the lack of control and standards.  Even when following a basic outline for standardized testing, different companies follow varied procedures that can skew the results of the hardness test.  One method is to lower the gram load weight of the pencil hardness tester.  The less pressure used in the tester, the less likely the surface is to scratch. This allows a tester to up the rating on their pencil hardness scale. This tactic is not outlined in the standardized testing, so it can go undetected by customers.  When choosing coatings based off the pencil hardness test, always look deeper into the testing methods as you are not always comparing "apples to apples."

Can a hard surface be scratched?

Absolutely, yes. The reason is relatively simple.  When the surface area of whatever material is making contact with the hard surface is very small but maintains equal acting force, the pressure becomes so extremely great, that the surface can then be penetrated. Much like how a mosquito can penetrate even the hardest of surfaces like a rhinos hide.

Curing ceramic 9H coating

Another factor is time. Many coatings take days, weeks, and even months to reach maximum hardness. When curing is accelerated through heat, for some coatings, the hardness may increase faster. But this is not always the case.

So what factors should I use when deciding?

All of the above and most importantly the proven durability (not claimed), installation qualities (is it easy to install or difficult along with why?), the group of installers who also chose to use this coating, and the actual warranty information. There are plenty of honest, proven coatings on the market. As always, through due diligence, use all of the research methods possible to first learn the most you can before choosing a coating. Sometimes it's not as easy as comparing apples to apples.

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