What is a sapphire mirror? Can sapphire be scratched?
1. What is a sapphire mirror?
Sapphire mirror, also known as sapphire crystal, generally refers to artificially synthesized sapphire, which is very different from the jewelry that people usually understand – natural sapphire, and is generally used in the manufacture of watch mirrors. It is a wear-resistant material along with tungsten-titanium alloy and high-tech ceramics. Although these materials are wear-resistant, they cannot withstand strong impacts. At the same time, some materials with the same or higher hardness (such as: grinding stones, sandpaper, nail files, granite surfaces, concrete walls and floors, etc.) may scratch the surface of these materials.
2. What are the characteristics of sapphire mirrors?
Sapphire crystal itself is a colorless, transparent, high-density, and brittle material; various chemical elements can be added to generate different colors. The hardness is Mohs 9, second only to diamond. Sapphire mirrors are more wear-resistant and scratch-resistant, but due to their high hardness and brittleness, they are easily damaged when they are hit or dropped!
3. Will sapphire mirrors be scratched?
In daily life, the anti-scratch effect of sapphire mirror is much better than that of ordinary mineral glass, but it does not mean that sapphire mirror will not be scratched. One situation is to encounter something with higher hardness. We know that the hardness of diamond is higher than that of sapphire, but if you rub the mirror against sand, marble, and granite, it will also be scratched, because the impurities in these stones contain diamond components, so it is necessary to avoid friction between the mirror and rock-like materials. Another situation is to be subjected to great force. The reason is very simple. For example, bullets are lead. We all know that lead is softer than steel, but bullets can indeed penetrate steel plates. Therefore, no matter how high the hardness of sapphire is, it can be scratched by great force! Once sapphire is scratched, it is difficult to polish it, and the only way is to replace the mirror.
4. The sapphire mirror itself is colorless, so why does the reflection of the watch mirror usually have color?
The reflection of sapphire itself is colorless, but many watches now use AR coating on the mirror. AR coating will show blue, green, purple and other reflections, which are commonly referred to as blue coating, green coating and purple coating. Of course, in addition to sapphire mirrors, many low-end watches use ordinary glass that is also coated. The cost of coating is not high, so many merchants use ordinary glass coated with blue film to deceive consumers and say it is a sapphire mirror. Some consumers even think that there must be blue reflection to be a sapphire mirror. Once I had a customer who refused to accept the IWC Portuguese Chronograph because he said, “Your watch mirror has no blue light, it is not a sapphire mirror!” I explained for a long time but he still didn’t believe it. In fact, the mirror of the Portuguese Chronograph itself is not coated with blue film. Speechless O__O’…!
There is a problem here. Sapphire itself has a good scratch resistance, but the coating is very easy to be scratched. Some consumers use a needle tip to scratch the mirror surface and find that it is scratched with a slight scratch. They think that the mirror surface is scratched, but it is not, it is just the coating that is scratched! Someone may ask, “Since the coating is easy to be scratched, why do mirrors need coating?” Because the reflectivity of mirrors is usually around 4%, and the reflectivity of coated mirrors is within 1%, so that the mirror surface will be very transparent even in the light, and the scale will not be unclear due to reflection even in strong light! Then someone will definitely ask, “What if the coating is scratched?” There is a thing called polishing cloth on Taobao, which is very cheap and can not only polish the mirror surface but also the case and strap!