What's the "H" for Surface Hardness level?
When you take a close look at some packages of screen protection film or glass, you can often find "9H Surface Hardness" or "3H Surface Hardness".
Nobody knew what exactly it was. Maybe the bigger number we get, the better?
Today, I would like to unveil what it is.
What is the surface hardness?
Technically, the official name is "paint general test method - Part 5: Coating film mechanical features - Section 4: Scratch hardness (pencil method)" specified by JIS. It is a standard to show the hardness of the paint coating film and scratch resistance with numbers.
Detailed information is on the Japan Industrial Standards Committee (JISC) page. It has been mainly used for the strength of paint films such as automobiles. Recently, it is often used to prove the hardness of the surface hard coat layer of protective film for smartphones.
As you can see from the JIS title, "Scratch Hardness (Pencil Method)", the expression H or 3H represents the hardness of the core of the pencil. The hardness of the core of the pencil is hard in the order of 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H.
· Rub it against the polishing paper vertically so that the tip of the core becomes flat.
· Add weight of 750 g ± 10 g to the pencil while the core tip is on the paint coating.
· Pencil angle should be set at 45 ± 1 degree.
· Measure at a speed of 0.5 mm to 1 mm / s by moving it more than 7 mm.
· Repeat the test by raising the pencil hardness until the scratches can be seen are generated.· The hardest pencil hardness which did not cause any scratches is going to be used as its corresponding hardness.
Although this test can be measured by hands, JIS recommends using special equipment in order to accurately measure.
With this machine, you can accurately measure with weights and angles.
About The Testing Pencil
According to JIS, they recommend the Uni, MITSUBISHI PENCIL for the test. If you check HP of MITSUBISHI PENCIL,
There is a description: "When using pencils for strict test, we recommend "Pencil for scratch hardness test" of the Japan Paint Test Association."
This scratch test pencil has 14 kinds of hardness: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, and 6H.
The problem is what to do if you want to achieve a hardness of over 6H.
Although it may be the unnecessary hardness standard for ordinary paint film, but for the smartphone screen protector, the harder the better.
Therefore, we are using the pencils of MITSUBISHI Hi-Uni series for testing.
On the packages of glass protector from Simplism, it is described as 9H, 10H or more, this means that they are tested by using Hi-Uni's pencil.
As a matter of fact, the surface hardness of glass is much harder than the pencil hardness, so even 10H cannot make any scratches. However, we still use this "H" in order to convey the surface hardness to the customers.
The pencil hardness test is conducted accurately to all the Simplism products accurately.
Now you finally got the idea that the "H" means.
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