How to identify sapphire glass?
The identification of sapphire glass is similar to that of jewellery, and the instruments used is also the same. The most commonly used instrument for jewellery identification is the refractometer, which can determine the refractive index of the detected thing. Although sapphire glass is an artificial material, its refractive index is identical to that of natural sapphire, which is 1.76~1.77. Sapphire glass is a crystalline material, and as such, it has a heavy refractive index like a crystal, which is 0.008. This can be seen clearly by rotating the polarizer on the eyepiece. The surface of flat glass is the optimal area for observation, whereas the spherical glass is less suitable. When testing, it is necessary to coat the glass with refractive oil. Mineral glass has a refractive index of approximately 1.52, and it has no heavy refractive index, which differentiates it from sapphire glass easily.
Another way is to use a polarizer, which enables the examination of all crystals. This includes sapphire, which is also a crystal. When a polarising is rotated, alternating light and dark changes occur, with each rotation of 90 degrees constituting a cycle. However, when utilizing a polarising to examine the watch glass, it is necessary to take out the entire watch center and expose the watch glass. Nevertheless, it should be noted that some non-sapphire glass may also exhibit a polarizing effect, given that it has also been manufactured into crystals.
The third method of testing sapphire glass is dropping water. That is, with a small drop of water dropped from a higher place to the surface of the glass, if the water drop is observed in a high bead shape, then it can be concluded that the glass is sapphire. Conversely, if the water drips apart, it can be inferred that the glass is not sapphire. Any liquid, regardless of its composition, will exhibit a different liquid level when dropped to a smooth medium surface. This phenomenon, known as liquid tension, is also related to the properties of the medium and temperature, which can be quantified by measuring the angles as well. Furthermore, the technical index is also applicable to watch oil. This method can be employed to identify sapphire, as the density and specific gravity of sapphire are relatively high, and the surface is more smooth and delicate.
