Tuesday, November 29, 2011

What's the difference between acrylic, mineral, and sapphire crystals?

The see through window above the dial is commonly interpreted as Crystal.

An acrylic watch crystal is a kind of plastic, being ductile, which has the advantage of being resistant to shattering, but prone to be scratched quite easily. Fortunately, scratches can be easily removed from acrylic. See Note*1 below for rework.
Mineral crystal is a kind of glass, which is more scratch resistant than acrylic, but not as as good as sapphire. Mineral crystals are also somewhat better at shatter resistance compared with sapphire. Unlike acrylic, scratches in mineral glass are more difficult to buff out; and unlike sapphire, mineral glass will scratch. In my opinion, the mineral crystal seems to be a poor compromise between the two extremes.
A sapphire crystal is indeed made of synthetic sapphire industrially, which is a transparent form of corundum, or aluminum oxide (Al2O3). It is extremely hard (Moh's scale 9), theoretically it will resist scratching by most substances short of diamonds. However, if it is struck sharply from the right direction, sapphire will crack. Despite the relatively large size compared with sapphire gemstones, sapphire crystals aren't very expensive (approx. $20). However some of the curved synthetic sapphire can be a few time more expensive as due to the manufacturability.
A cheap Fake watch usually used Mineral Crystal which is not as clear and transparent as the Synthetic sapphire. This is one of the way the tell this is Grade B or Grade A Fake Watch. Some grade A Fake watch uses synthetic Sapphire!
Attached Picture is a Older Rolex Day Date Ref. 1803 dated 1972 which was only having
Acrylic Crystal, where the newer Day Date Ref 18338 dated 2003 on the right is using Synthetic Sapphire.
Rolex Acrylic Crystal is just HKD$250 and a Synthetic Sapphire is approximately HKD$900.
A Rolex Acrylic Crystal is warmer and the new synthetic Sapphire is cooler when you place you watch to you cheek.. some of the people prefer the older watch just because they warm they are warmer….more closer to the skin temperature!
How do I remove the scratches from an acrylic crystal?
Good old-fashioned toothpaste is a good start. Start by buffing a little bit onto a clean fine cloth over the area of the scratch. Rub lightly, and rinse with a very slightly damp cloth. Repeat until scratches are gone.
Note that there are also purpose-made polishes for this purpose, such as Polywatch , Crystal-Kleer or Brasso. Tsim Sha Tsui Snob

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