How to tell the material of watch glass?

　　Watch glass is an exterior component, situated in the most prominent part of the watch, with the most opportunities for friction and impact with the outside world. Due to the material and position, the watch glass is one of the most easily damaged parts of a watch. Whenever the watch glass is lost, broken, or has cracks, it must be replaced according to the original specifications.

　　Classification of watch glass materials

　　Sapphire crystal: Stable in physical and chemical properties, with a hardness second only to diamond. It solves problems such as scratching, ageing, and corrosion, but is fragile. (Generally used for high-end watches.)

　　Plexiglass: That is synthetic glass, commonly known as acrylic. It is prone to scratches, but has good toughness and is not easily broken. (Mostly used for entry-level watches.)

　　Mineral glass: Has better scratch resistance, but its resistance to vertical impact is stronger than that of sapphire crystal, which is why military watches mostly use it for watch crystals. (Used for mid-range and entry-level watches.)

　　Methods for distinguishing watch glass materials

　　There is a professional hardness testing pen that can measure the hardness of the glass, but without professional equipment, you can use the following methods to distinguish:

　　First, when you gently tap the surface of plastic glass with your finger, it will emit a sound like plastic, whereas the sound of glass is thicker and more solid;

　　Second, you can touch it with facial skin. Touching sapphire crystal gives an icy sensation that other glasses do not have;

　　3. You can perform a water droplet test; a droplet will maintain its bead shape and will not easily spread out on sapphire crystal, whereas it will disperse quickly on other materials;

　　Additionally, what is an anti-reflective coated crystal? Simply put, an anti-reflective coated crystal features a thin film electroplated onto the lens to prevent light refraction, much like solar control film on car windows or coated lenses on spectacles, and is commonly used in professional aviation, diving watches, or watches with curved crystals.