Momentum Watch Steelix Ivory SE 44MM Goma Rubber

Momentum Watch Steelix Ivory SE 44MM Black Dial with Black Goma Rubber

The Momentum Steelix 44mm Watch in Ivory comes a Black Goma Rubber watch strap, a virtually scratch-proof Sapphire Crystal and designed with a unique dial/handset. The propeller-shaped hands with super-luminous paint you to see the time even in the darkness of the night. The Steelix has a casing which is made from a block of solid 316L stainless steel and packed with all the features a great Momentum Sports/Dive Watch is known for.

Scratch-Resistant Sapphire Crystal

What is Sapphire Glass?
Synthetic sapphire combined of crystallised aluminium oxide

Astonishingly Sturdy
Value of 9 Mohs of mineral hardness same as titanium carbide

Scratch Resistant 
Superior to Quartz or gorilla glass

Application

• Watch Glass
• Display 
• Optics

Synthetic Sapphire: 
A synthetic sapphire crystal or “glass” is actually not glass at all. It is a very hard, transparent material made of crystallising pure aluminium oxide at very high temperatures. Synthetic sapphire has the same hardness as natural sapphire gemstones, but without the colouring agents that give the gems their various hues. When it is heated, the synthetic sapphire forms round masses, that are then sliced into pieces with diamond-coated saws. These disks are then ground and polished into watch crystals. (One reason sapphire crystals are relatively expensive is that the tools required to cut and polish this extremely hard material are very costly.) Sapphire (whether natural or synthetic) is one of the hardest substances on earth. It measures 9 on the Mohs scale, which is a system for rating the relative hardness of various materials. (Diamond measures 10, the highest rating.) Watch crystals made of synthetic sapphire are often marketed as “scratch resistant” or “virtually scratchproof” because they are very difficult - but not impossible - to scratch. Diamond can scratch them; so can man-made materials that incorporate silicon carbide, which, with a Mohs rating of between 9 and 10, is harder than sapphire. So, if you accidentally scratch your watch on a simulated-stone surface or a wall that incorporates some of these silicon carbide materials, it could scratch the crystal.

AR Coatings:
Sapphire crystal is more reflective than mineral crystal due to its higher index of refraction. (1,8 compared to 1,47). Applying one or more layers of AR (anti-reflective) coating will limit this reflection to a very low level. Very often, lines and marks on the top surface of a sapphire crystal are mistaken for scratches but are actually the scratched AR coating, or just AR coating wearing off after time. An AR coating on the inside of the crystal provides a good AR performance while avoiding this problem. If you do scratch a sapphire crystal, then it cannot be polished away and will need to be replaced.
 
Waterproof gasket:
As both mineral and sapphire crystals are extremely hard, they have little or no “flex”. This means that when the crystal is inserted into a hard, steel or titanium watch case, it requires a gasket to ensure a waterproof seal.  These crystal gaskets are typically made of nylon, and are either flat, “I”-shaped or “L”-shaped. (see example above). The crystal is pressed into the case, using a crystal press tool. When it is pressed in, the nylon crystal gasket is “squeezed” between the crystal and the case rim, making a reliable waterproof seal. Over time, these crystal gaskets can become brittle and break, so it is a good idea to change the crystal gaskets every few years, to ensure the ongoing waterproof performance of your watch.