Mengus Watch Tech – Episode 4

Episode IV – Watch Crystals

If we can’t use the practical information in daily life, that we learn from reviews or articles, then what is the purpose of spending time reading them in the first place?

Lots of things are talked about in forums and FB groups about watch crystals. If it’s not sapphire, then it’s not worth having, according to many.

Here are the typically used materials in their scale of hardness:

  • Sapphire
  • Hardlex
  • Mineral
  • Acrylic
  • Polycarbonate

In reality the crystal material does not make too much of an effect on the watch you’re wearing, if you do not count price. It’s all about the benefits that particular crystal gives. By the end of this article, you will understand what I mean. The most expensive material in market is artificial sapphire crystal. The ranking is close to “8-9” at MOHS scale (a hardness scale for gems) very close to diamond. Yes, in all aspects, sapphire is very scratch resistant but not scratch proof. Realise the difference. You can scratch or shatter sapphire. It is hard but not impossible. Sometimes you see a beautiful blue tint in sapphire crystals. This is directly related to the quality and thickness of sapphire and the Anti Reflection Coating (applied layer on surface to prevent glare). This treatment prevents glares and reflections and increases legibility. You may hear of “Double Domed” crystals. This has nothing to do with the size, what it means is that the outside of the crystal is concave, whereas the underside is convex. This allows for less distortion, especially at depth.

HINT: Always chose internal AR coated sapphire crystals. Externally treated crystals will start to peel because of friction, and a very nasty looking appearance occurs on surface.

How do we know if a crystal is sapphire or not?

It is hard to prove if a crystal is sapphire or not. Jewellers and watch makers use special tester apparatus or needle apparatus. This is the same as used to detect if a diamond is real or fake.

HINT: You can ping the crystal with a steel or nail (try not to scratch it). If the sound is treble, it is probably acrylic or polycarbonate. It’s not a foolproof method because hardlex and mineral crystals also have strong bass sounds.

HINT: Another common way is dropping water on surface.

Water drop test. If a drop flattens on crystal, It is not sapphire. Probably acrylic or polycarbonate.

If the drop stays round and domed. Crystal is probably sapphire.

Best way to define sapphire or not is the tester pen apparatus however.

What about mineral crystals, acrylics and polycarbonates.?

Mineral crystals are quite durable. Mineral choice may decrease the price by USD 30 to 80 when you are choosing a watch. It is not possible to determine if a watch has a sapphire crystal or mineral crystal, simply by looking.

The crystals are fixed in case in 2 ways: Use an “ I ring” (made of nylon and holds crystal by friction) and UV glue. I ring gaskets may cause water leakage after time due deformation and if exposed natural abrasives like acid, base contact etc. UV glue is a kind of chemical that start to bond under UV light only and fixes the crystal in its nest.

A nice watch, called the Vostok Amphibia diver series, uses acrylic in a clever way. This watch is AK 47 of watches. It is a completely amazing design. The crystal is flexible because it’s made of acrylic but hard and thick enough to counter to 200 m (20 atm) pressure. Acrylic crystals becomes flatter when water pressure increases, and from the sides this squeezes and holds the I Ring tighter. The deeper the depth, the tighter it becomes. Besides, acrylic decreases the price tag of watch. Another incredible part of this watch is the backlid. A separate ring keeps the backlid rubbing and deforming the backlid gasket. We will cover water resistance issue in a separate episode. I Hope Tony will do a review one of these Vostok Amphibia soon. (Hmmm, I don’t like them as much as you do Mengu – Tony)

Any questions are welcomed. Any point in your mind, I will try to give an answer. Keep your watch crystal clean, till next episode!

Author: Mengu Evrensel

Watch designer, maker, artist, guitar player

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