A watch crystal is a transparent cover that goes over the dial and protects it. As you might imagine, it has to be transparent, else how the hell are we going to see?
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Types of watch crystals
There are three types of crystals used in watches; Sapphire, mineral, and Plexiglas or acrylic crystals. Plexiglas or acrylic is the cheapest of the lot and sapphire is the most expensive.
Plexiglas or acrylic
As this one is modest of the lot, it is used in low-cost watches. It is extremely flexible and virtually shatterproof. But this one is the most scratch-prone material. So, if you are buying a kiddie’s watch, go for this one, at least there won’t be any cracks!
This one falls in the mid-range price category. Mineral crystals are nothing but ordinary glass treated at high temperatures or special chemicals to make them tougher and scratch-resistant. While they are not as scratch resistant as sapphire but are definitely better than acrylic. Most of the watches used this type of crystal. Some brands create their own version of mineral. Like SEIKO uses a proprietary mineral called HARDLEX in most of their watches.
Now before your mind races and starts thinking of this as a precious gem, stop! Original sapphires were used quite a few decades ago, not anymore.
These are made in laboratories and in a furnace!
To be a bit scientific, these are made from powdered aluminum oxide particles that are sprinkled through an oxyhydrogen flame, and expected to melt at temperatures over 2000 degrees Celsius!
Once they cool down below the melting point and fuse with one another, they begin to re-crystallize.
What you get eventually is a long cylindrical rod of sapphire which is cut by diamond-tipped cutters (as nothing else can cut it) and polished.
These are quite scratch and shatter-resistant.
There are real-life accounts of Rolex users, who accidentally banged their watches against a door or wall. The crystal didn’t crack or scratch, but the poor wall did!
Most high-end watches use this crystal and these are the most expensive of the lot.
How do you tell if your watch has which crystal?
The water drop test
Place on a drop of water on the crystal.
If the drop is well-formed, it is most likely a sapphire or else it is mineral/acrylic.
Now tilt it allowing the drop to slide. If the drop moves without leaving traces, it’s a sapphire. If it creates a puddle or a mess, its mineral or acrylic.
The sound test
Gently tap it with a fingernail.
While sapphire should give a thud sound (more bassy), the mineral will give a click (like how glass sounds).
Acrylic will also give a click but will sound more like plastic.
The forehead test
Yes, you heard it right, but you don’t have to bang it against your forehead! Instead, place the crystal on your forehead.
The acrylic should be the warmest and the coldest should be the sapphire.
Go ahead and find the truth of your watch crystal! What is it made of? What test did you perform?
Hit the comment box!