The Origin of Sapphire Crystals on Replica Watches

　　The watch glass, as one of the most vital components of a replica watch, primarily serves to keep out external dust and moisture, thereby protecting the dial, hands and movement. However, watches were not originally designed with a crystal; instead, they used a protective cover. As manufacturing techniques matured, watchmakers began using silicate glass for watch crystals, alongside natural crystal options.

　　The application of sapphire dates back to the 70s, when the glass crystal materials used in watches were roughly divided into:

　　1, Plastic Perspex: Also known as acrylic or resin glass, this type of watch crystal is very prone to scratching and has slightly lower transparency, but because it is resilient and resistant to shattering, it is also called "safety glass". It is most commonly found on older watches.

　　2, High-hardness mineral glass: Also referred to as mineral crystal or hardened glass, this material is used in the majority of modern watches. Crystals made from this material resist scratching well, but because their hardness exceeds that of plastic perspex, they are more susceptible to shattering.

　　3, Sapphire crystal glass is not natural sapphire, but rather a synthetic material with a density and hardness equivalent to that of sapphire. It possesses extremely high density, with a hardness second only to diamond, ensuring it will not be scratched by daily bumps. Nevertheless, due to the high hardness of sapphire crystal, a severe impact or drop from a height may cause it to crack, though it will not shatter completely or fall out. In addition, many sapphire crystals feature an anti-reflective multi-layer coating on both sides to prevent light refraction. For instance, the specially treated double-sided multi-layer sapphire crystal on Breitling watches disperses light sources, which is particularly effective at high altitudes in direct sunlight, allowing the wearer to read the time clearly under the blazing sun.

　　How to tell if a sapphire crystal is coated

　　The simplest method of identification is to tilt the crystal, as thin-film interference will produce a colourful prismatic effect (much like spectacle lenses).

　　When buying a watch, hearing that it features a sapphire crystal naturally makes it feel high-end. In reality, however, the sapphire used in watches is not expensive natural sapphire, but genuine synthetic sapphire. Let us explore how sapphire is manufactured.

　　Synthetic sapphire is made from alumina (aluminium oxide) mixed with oxygen and hydrogen.

　　During production, the alumina is first decomposed at a high temperature of 1200 degrees, after which the material is brought to its melting point of 2050 degrees. After 15 hours, it forms a rod-like boule. It is then fired once more at a high temperature of 1800 degrees to ensure structural stability.

　　Next, diamond-tipped cutting blades slice it to the required thickness, and after grinding, it can be shaped into a domed or semi-circular crystal surface.

　　Following the grinding process, the semi-finished product undergoes further chemical polishing to ensure a seamless fit with the case.

　　Immediately afterwards, these sapphire crystals are transferred to furnaces in a cleanroom laboratory, where they undergo anti-reflective treatment via a precision vacuum evaporation process.

　　Sapphire crystals that have undergone anti-reflective treatment reduce reflected light entering the naked eye by 99%, with that faint blue tint playing a key role.

　　By the way, there are two additional points to keep in mind:

　　1, The coating can be rubbed off, so avoid cleaning it with abrasive items. It is best to use a soft cloth such as a microfibre cleaning cloth.

　　2, The water droplet test circulating online is not an effective way to identify a sapphire crystal; retailers will usually tell customers this directly, given that they are inexpensive anyway. Alternatively, you can purchase a dedicated sapphire tester pen to test it yourself.