Watch glasses. Sapphire or Mineral?

Wrist Watch

It will not be a discovery for anyone that true lovers of wristwatches have a rather impressive collection. Some models are worn very often, and some - for the occasion. For example, classic Jacques Lemans with sapphire crystal - great watch for every day!

But for a solemn event, it is better to wear a watch that matches the evening look. For example, the elegant Candino with extra durable mineral glass. But, even such durable glass can be scratched.

Familiar situation? Yes, mineral glasses, albeit the most durable ones, “take a blow”, or rather, protect from scratches, quite differently than sapphire ones ... How are they different? And why are sapphire glasses ready to repel any attempts to scratch them, while mineral ones are losing ground?

When choosing, not all buyers pay attention to what kind of glass is installed in the watch. It would seem that this is not such an important detail. Meanwhile, it is the watch glasses that are designed to protect the dial, and sometimes the watch mechanism (in the case of a transparent back cover) from external factors: moisture, dust, etc.

Watch glasses can be of three types:

• The most inexpensive - plexiglass (light and transparent plastic)

Plastic glass is not so easy to break, but it can be scratched with ease, however, it is very easy to polish.

Among the disadvantages: over time, such glass becomes a little cloudy. As a rule, these glasses are used in inexpensive watches.

There are enough models with plastic glasses in the Casio collections.

• The most popular is mineral glass (similar to window glass)

Even after tempering, mineral glass will still crack faster than plastic glass. But on the other hand, it does not scratch so quickly and does not grow cloudy.

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This type of glass is used in watches of the middle price range, and sometimes you can find the inscription CRYSTAL GLASS on the case back. You've probably heard about high-strength mineral glasses: a special hard coating makes the glass more resistant to mechanical damage.

For example, one of the variants of such glasses (hardlex) is used in many (inexpensive) Seiko models.

• The most expensive - sapphire crystal (synthetic sapphire formed during high-temperature processing from crystallized aluminum oxide)

Its main characteristic is high scratch resistance. Sapphire (natural or synthetic) has a hardness of 9 on the Mohs scale, second only to diamond with a hardness of 10.

However, the hardness of the material makes sapphire crystal very fragile at the same time. It breaks more easily than plastic or mineral. The use of expensive tools when processing these glasses is one of the reasons for their high cost.

It is logical that sapphire crystals are installed in watches of premium and luxury brands, and on the back of the watch or on the dial there is the SAPPHIRE or SAPPHIRE CRYSTAL markings. By the way, synthetic sapphire has been used in the watch industry since the 60s.

Often, sapphire or mineral glass is applied anti-reflective coating - on one or both sides, it is covered with a special very thin film, also used for camera lenses or glasses. This coating reduces light reflection so that readings can be read easily even in the brightest lighting conditions. How can I see this coverage?

Look closely, see a subtle bluish tint? This is precisely the anti-reflective coating.

How can you tell the difference between a sapphire crystal, you ask?

It is impossible to distinguish mineral glass from sapphire glass by eye: they look almost the same! The right way to check: trying to scratch the glass :-) Another test is not so radical: hold a watch with a mineral and a sapphire crystal alternately in your hands. They react differently to temperature changes. Sapphire heats up more slowly.

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In addition to the main types of glass that have been mentioned, manufacturers use others as well. Stuhrling watches are equipped with unique Krysterna ™ glasses - scratch-resistant, like sapphire, and mechanically strong, like mineral.

There are also combined glass: one, thick layer - mineral glass, and on top - a thin layer of sapphire. In terms of quality and characteristics, they are not inferior to sapphire glasses, but at the price they will definitely give a head start! Such combined glasses can be found in the collections of Adriatica, Seiko, Rodania, Swiss Military Hanowa, Nina Ricci.

Just like watch cases, glasses can be of different shapes: round (lunette) and curly (shaped crystal), that is, all the rest... Glasses are distinguished along the profile: flat, spherical, lens-shaped and more complex shapes (for example, with a faceted surface like Chronotech).

The thickness of the glass can also be very different. Standard: 0,8mm to 1,2mm. This is enough for hours every day. But when choosing a watch for diving, keep in mind that the glass must be at least 1,2mm thick. In addition to the thickness of the glass, its shape also plays an important role. Convex glass is the best way to distribute pressure on its surface, which means it is ideal for diving watches. A great example is Oris in the Divers collection.

How to care for watch glasses?

  • Wipe the glass with a soft cloth
  • Avoid direct hits

And remember that any glass, even the toughest glass, can be broken!

What if the glass is broken?

  • Stop the watch (by pulling out the crown) to avoid damaging the movement
  • Contact an Authorized Service Center
  • Never try to change the glass at home. Only highly qualified professionals working in special conditions can carry out the replacement.
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In any case, it is hardly worth giving up buying a watch of your dreams just because there is not the desired type of glass.

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