Types of glasses in watches
Glass in watches, whether they are ordinary or "smart", plays by no means the least important role. At a minimum, he is responsible for protecting the dial from mechanical damage and from getting inside the watch case of dust and other contaminants. The type of glass placed on the first line of defense of a chronometer also directly affects its strength characteristics.
There are not so many options for watch "glazing". The main ones are the following:
The most affordable material that covers the dial of a wristwatch is found mainly in the equipment of budget models and some representatives of the sports watch family. In particular, such glass is installed on board fitness trackers and, for example, a wrist “combine” for runners Garmin Forerunner 735XT — multi-sport watch with advanced functionality.
|Due to its flexibility, plastic glass can be molded into any shape.|
Advantages of plastic glass:
- low cost - it is not difficult to replace plastic glass in the event of such a need;
- high strength due to the soft and plastic structure - under the influence of impacts, the glass often bends, it beats much less often;
- the ability to give any shape, both flat and convex;
- easy to polish, which eliminates the first of the list of disadvantages below.
Disadvantages of plastic glass:
- actively collects scratches;
- quickly becomes cloudy due to the appearance of microscopic roughness;
- absorbs moisture - sometimes when the humidity is too high, fogging of the glass occurs from the inside, which makes it difficult to read the readings from the dial.
Mineral glass is ranked among the most common material used to make protective coatings for watch dials. It occupies an intermediate niche between cheap plastic glasses and more expensive sapphire glasses, being an optimally balanced “golden mean”. The names related to the material are silicate glass or artificial crystal.
|Mineral glass is used in the vast majority of watches|
Benefits of mineral glass:
- good transparency, which ensures excellent visibility of the readings on the dial or display (if it comes to smartwatches);
- easy to polish, which helps to get rid of scratches even at home.
Disadvantages of mineral glass:
- low impact strength - under the influence of impacts, mineral glass cracks or breaks, while the fragments can turn out to be quite sharp;
- susceptibility to catching glare - when exposed to direct sunlight, the readability of the dial deteriorates.
The last disadvantage is solved by applying an anti-reflective coating, which is practiced by many chronograph manufacturers. It allows you to see what time it is in bright sunlight or artificial light.
In addition, mineral glass can be enhanced with a sapphire coating to make it harder and therefore more resistant to scratches. Tempering also helps to improve the mechanical properties of glass.
An expensive material created on the basis of artificially grown corundum crystals. In terms of hardness, sapphire glass is inferior only to diamond and its compounds (9 points on the Mohs scale against 10). He is the only one who can scratch the sapphire crystal, since it is almost impossible to do this in domestic conditions.
|Sapphire crystal can be found in the equipment of some modifications of the Apple Watch|
Advantages of sapphire glass:
- no tendency to scratches;
- does not become cloudy and does not fade over time, while maintaining excellent transparency;
- has little susceptibility to glare.
Disadvantages of sapphire glass:
- high cost - sapphire glass on top of the dial or watch screen is a sure sign of the high status of the product;
- brittleness with direct point impacts, because hard does not mean high strength. It is advisable not to subject the sapphire glass to strong impacts, otherwise (for example, if the watch falls on asphalt), it may break into smithereens and shatter into small fragments.
"Sandwich" from different types of glass
Some types of watch "glazing" borrowed the best from the trinity of the above types of materials. So, saflex (Sapflex) combines the hardness of sapphire and flexibility in order to withstand heavy loads. Hardlex, a proprietary development of the Japanese watch brand Seiko, has similar properties. Structurally, hardlex consists of a mineral base, which is subjected to hardening and subsequent chemical treatment, as a result of which the outer layer of glass is compacted due to the displacement of some and metal ions by others - more durable.
|Hardlex glass is standard on most Seiko watches. The Japanese brand also sells this glass to a large number of third party manufacturers.|
One of the latest solutions in the watch industry is Krysterna glass, which came from the eyewear industry. This material combines sapphire scratch resistance and mineral mechanical strength. You can meet Krysterna glass in wristwatches from the Stuhrling brand, which participated in the entry of a new material into the industry.
The rapid development of the wearable electronics market forced the introduction of Corning Gorilla Glass, which has proven itself in the field of smartphones, into watches with the “smart” prefix. They are thin and strong at the same time, they perfectly resist scratches, and the latest generations of "gorilla glasses" are also practically not inferior in properties to sapphire ones. Especially for wearable gadgets, a special Gorilla Glass SR + glass is produced, which provides excellent strength, optical permeability and touch sensitivity.
|Corning manufactures screen protectors for most current smartphones, some laptops and smartwatches.|
Gorilla Glass is not used in classic wrist chronographs. But in "smart" watches and bracelets, various generations of this material are found with might and main, combining relatively low cost and good reliability. And if in smartphones the protective “gorilla glass” sometimes forms a “spider web” of cracks all over the screen when the gadget fails to fall, then in the family of wearable devices this problem is reduced to nothing, since the watch screen area is much smaller than the mobile phone display.
Good luck with your choice!