Will sapphire crystal wear out?

　　Using sapphire for the watch crystal certainly has major advantages, as it is difficult to scratch and wear down due to its hardness rating of 9, second only to diamond. So, can sapphire watch crystals get scratched? Let us take a look below.

　　Sapphire crystal can indeed be scratched. In earlier years, Rado advertised their watches as being "scratch-proof", which was clearly an exaggeration; this was later changed to scratch-resistant, which is much more accurate. Indeed, sapphire crystal is merely scratch-resistant, and anything hard tends to be relatively brittle. Therefore, sapphire crystal is easily cracked or shattered under severe impact. (See photo)

　　Additionally, when sharp objects scrape across the surface of the crystal, they can easily cause scratches. This depends on the force and speed of the scrape; the sharper the contact point, and the greater the speed and force, the easier it is to cause a scratch. Another factor is the angle of impact; an impact angle of around 45 degrees is more likely to cause significant scratching.

　　In the late 80, when Swiss watchmaker Rado came to China to promote its tungsten-steel case and sapphire crystal watches, they performed live demonstrations on the spot. They placed the watch on the ground with the crystal facing down, stepped on it with one foot, and rubbed the watch back and forth against the ground under the pressure of a leather shoe. After the experiment, they wiped the watch clean, and remarkably, both the case and the crystal were completely undamaged, looking as bright and new as ever.

　　The Chinese spectators present at the time were astonished. Having never seen such a durable and scratch-resistant watch before, they thought it was miraculous. Looking back now, I feel that it was a gimmick, akin to a magic performance by Liu Qian. In reality, this is a simple matter of common physical pressure: the key lies in the fact that the contact area between the crystal and the ground was very large, while the pressure and rubbing speed from the foot could also be controlled by the person.

　　In watches like Rado models where the exterior surface is made entirely of protruding sapphire crystal, the edges are most vulnerable to damage. Crystals that are fully embedded into the case are relatively safer.

　　Once a sapphire watch crystal is scratched or marked, it cannot be removed through grinding and polishing; in other words, it cannot be repaired and must be replaced with a new one. Flat circular crystals are relatively easy to replace, but arched or shaped crystals generally require sourcing original parts, and the cost will not be cheap.