JerryRigEverything’s Zack gets to the bottom of this question in a new teardown video. Part of these videos is always a scratch test, in which Zack treats the displays with objects of different hardness. The hardness is given on the Mohs hardness scale. “Normal” Gorilla Glass scratches from level 6 or 7, depending on the generation. Real sapphire glass, on the other hand, achieves a value of 8 to 9. Here is the test of whether the Apple Watch Ultra really has a sapphire glass display.
Sapphire crystal is man-made, extremely expensive and almost as hard as diamonds. Since the iPhone 5 and Watch 3 generations, Apple has stated that the displays are made of sapphire glass. Technically that’s even true, but it’s a below-average hard version of sapphire glass that’s cheaper to manufacture.
Two different Sapphire tests
In the test, Zack uses two methods to check whether it really is high-quality sapphire crystal. On the one hand, a test device is used that measures the thermal conductivity of a material. The higher the conductivity, the higher the quality of the material. On the other hand, various scratching tools of different hardness are available. A Samsung Galaxy Watch5, the Garmin Fenix 7 and the Apple Watch Ultra are tested, all of which have sapphire glass displays according to the manufacturers.
First up is the Galaxy Watch5, which according to the test device actually uses a sapphire glass panel. However, the measurement only just reaches the limit of the red area. The scratch test only leaves real damage from level 8, which confirms the measurements of the device. The Garmin Fenix 7, on the other hand, almost exceeds the range of the test device and shows the maximum deflection. The scratch test shows the well-known picture – scratches from level 8, it is a real sapphire glass.
Now to the Apple Watch Ultra: The test device shows almost full deflection, only a line is missing at the end of the scale. The scratch test shows minimal scratches from level 7, with stronger marks from level 8. Zack therefore assumes that Apple is still using the same type of sapphire glass as always. While the Garmin Fenix 7 emerged as the winner of the test, it is also clear that the Samsung Galaxy Watch5 and the Apple Watch Ultra have sapphire glass installed. The glass of the Garmin is just a bit harder.
