Past sapphire glass was only used for high-end replica watches swiss and was very expensive, if it is the polymorphic glass watch, for example: arch, ball, polygon, the production process is even more difficult. Now it is very common that watch uses sapphire glass, which has been seen in many watch brands due to a large number of applications, especially the thin plate-like glass, the cost is not high and the price is not expensive.

We know that the biggest advantage of the sapphire glass is very hard and durable, which is very important for the long-term maintenance of watch’s intactness and beauty. Therefore, if a watch uses the sapphire glass, it will be written the English mark “SAPPHIRE.”
 
Sapphire watch glass is also helpful for improving the water resistance, especially the diving watches, can dive 300 meters, and the adopted sapphire glass’ thickness reaches to about 3 to 4 mm, so as to withstand the tremendous pressure of the deep-sea.

The cultured watches are plated with a layer of film on the sapphire glass, which has effect on preventing the anti-reflection and increasing the transmissivity. This is the same as the spectacles glasses and camera lens; some watches are even plated layer of film on both sides of the glass.

So, how to identify the sapphire glass?

(1) Laboratory methods:

To detect a watch glass is a sapphire glass or not, which is very similar to the jewelry appraisal and using the same instrument equipment. The most commonly instruments of jewelry appraisal is the refractometer, which can determine the refractive index of the tested things.

Although the sapphire glass is artificial, but its refractive index is the same as the natural, both are 1.76 to 1.77, because the sapphire glass is a crystal, so it also has refractive index the same as the crystal, which is 0.008, this will be clearly seen by rotating the Polaroid in the process of detection.

Flat watch glass can be observed, while spherical face is hard to observe, when testing, you’d better daub the refractive oil. The refractive index of mineral glass is about 1.52, it is easy to distinguish it from sapphire, and it has no re-refraction.

Another method is to use polarized light microscopy; all crystals can be checked out using polarized light microscopy, such as crystal. Sapphire is also the crystal, when rotating the polarizer, there will be alternating light and dark light turning 90 degrees per cycle. However, using a polarizing microscope to check a watch, you need to remove the whole movement, exposing the glass. However, some non-sapphire watch glass materials may also have the polarizing effect; it is because that it is made of crystal, such as the words “Crystal.”

(2) dripping method:

The legendary sapphire glass dripping method to measure the sapphire crystal glass is to drip a drop of water on the glass surface, was higher if the drip significantly tends to be a pearl, the glass is sapphire; if the drip is spreading, it is not a sapphire glass. Although this is an old method, I had to experience it, this trick really works, as there is any scientific justification, is still unknown.

Any liquid thing, dripping on drop of water on its surface, there will be a different fluid levels, the specific condition is relevant to the material nature and temperature, it should be called the tension of the liquid, is also counted by angle, including the watch’s watch oil also used in this specification. I guess due to the larger density and proportion of sapphire and the more smooth and delicate surface.

(3) The identity of watch and the hardness of glass:

If it is a regular brand watch, sapphire glass will usually be printed on the back of the watch, or indicated in the English words “SAPPHIRE” or “Sapphire Crystal,” now even it is a fake watch or counterfeit watch, it is ordinary to use the sapphire glass. Testing the hardness of the watch glass can be used a similar sharp metal needle to draw rub the edge of the glass watch at the most inconspicuous, feeling very hard, there is the feeling of drifting metal, glass is not scratched, it should be the sapphire glass. Also heard tapping listen to the sound of glass method, I feel seem no scientific justification; because the size of the glass watch are different, you cannot knock hard.