How to break a tempered glass screen protector

I’m a big believer in kitting out smartphones with a screen protector. A good-quality tempered glass screen protector is cheap insurance against scratches and chips, and can keep your smartphone looking new for longer, and can help improve the value if you want to resell your phone down the line.

I always choose a good-quality tempered glass screen protector with a rated hardness of 9 Mohs.

Mohs is a scale introduced in 1812 by geologist Friedrich Mohs to compare the hardness of minerals. At position 1 is talc, a soft mineral, while at the top at 10 is diamond, the hardest. The unit is measured by scratching a material with picks of different hardness.

This makes Mohs a good way to measure how scratch-resistant a material is.

When a good-quality tempered glass screen protector has a hardness of 9, it means that there are a limited number of materials that can scratch it. Gold, silver, and aluminum have a hardness of around 3, steel has a hardness of 4.5, teeth and volcanic glass have a hardness of 5, and hardened steel has a hardness of 8.

Note that sapphire, which is used as the crystal for some high-end wristwatches, including the Apple Watch Ultra, has a hardness of 9.

But just how good are these screen protectors?

Let’s find out.

Here I’m pitting the ESR Armorite tempered glass screen protector against a few nasties.

Note that I’m testing the screen protector on a soft, yielding surface. I believe that it would be even stronger on a flat, unyielding surface such as a screen, but I wanted to give the screen protector the toughest test possible.

I rubbed it with a rock…

… a key…

… even a knife…