In the past, due to its expensive price, sapphire glass was only used in high-end brand watches. Especially the arched, spherical and polygonal sapphire, their craftsmanship is more complex. But now, sapphire glass is very common and is widely used in watch-making, its price is also much cheaper than before.
As you know, sapphire glass is very hard, wear-resistant, and for all watches that use sapphire glass, there is a “SAPPHIRE” identity on the caseback.
Sapphire glass can also improve watch’s waterproof performance, especially the diving watches, which can dive to 300 meters, the thickness of their sapphire glasses is up to 3mm-4mm, so as to withstand the enormous pressure in the deep sea.
But now, how to identify sapphire glass ? Following are some methods.
1, Use equipments to detect
Although sapphire crystal glass is artificial, it has the same refractivity as the natural sapphire, both are 1.76-1.77. Because sapphire is crystalline substance, so like the crystals, it has a birefringence, which is 0.008. This can be seen clearly when rotating the polarizer of eyepiece.
The flat crystal glass is easy to detect, but you have to smear some refraction oil on the surface when detecting a domed one. Refractive index of mineral glass is about 1.52 and it has no birefringence, so it is easy to distinguish between it and the sapphire.
2, Dripping method
Drip a drop of water on the glass’s surface, if the water drop is presented as beaded, then the glass is sapphire, if the water drop spreads out, then it is common glass, not sapphire. Although this method is not known by most people, it is very effective.
3, Check the identification and the hardness of the glass
On the caseback of a original watch, there is a “SAPPHIRE” or “Sapphire Crystal” identification and sapphire crystal glass is also widely used in replica watches. Besides, a sapphire crystal won’t scratch when you drag a razor across its surface.
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