There are not so many options of glass for watches. The main ones are the following:

Plastic glass

The most budget-friendly material used to cover wristwatch dials is commonly found in low-cost models and certain sports watches. This type of glass is frequently used in fitness trackers and, for example, in Garmin Forerunner 735XT — a multi-sport watch designed for runners with advanced features.

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 case of such a need;
  • high strength due to the soft and plastic structure — it tends to bend more frequently than it shatters under the impact.;
  • 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;
  • microscopic roughness leads to a rapid clouding of the surface;
  • 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.
Good to know! Plastic glass is also called hesolite or organic glass.
Watches with plastic glass

Mineral glass

Mineral glass, often referred to as silicate glass or artificial crystal, is a widely used material for crafting protective coatings on watch dials. Positioned between inexpensive plastic and pricier sapphire glasses, it strikes a balanced middle ground.

Mineral glass is used in the vast majority of watches.

Advantages 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 — mineral glass can crack or shatter upon impact, producing sharp fragments;
  • susceptibility to glare is evident when the dial is exposed to direct sunlight, leading to a decline in readability

The issue of glare is addressed by applying an anti-reflective coating, a common practice among many watch manufacturers. This coating enhances visibility 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.

Interesting fact. Mineral glass can be transformed into a magnifying lens, aiding individuals with visual impairments in viewing the dial's indications.
Watches with mineral glass

Sapphire glass

Sapphire glass, an expensive material derived from artificially grown corundum crystals, ranks second only to diamond in hardness (scoring 9 on the Mohs scale against 10). It is exceptionally resistant to scratches, making it nearly impossible to scratch in everyday conditions, with only diamond capable of doing so.

Reference. The Mohs scale, a measure of mineral hardness, consists of 10 reference minerals arranged by increasing hardness: talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum and diamond.
Sapphire glass 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 — the presence of sapphire glass atop the watch dial or screen is a clear indicator of the product's elevated status;
  • hardness does not necessarily translate to high strength, especially when it comes to susceptibility to direct point impacts. Avoid subjecting sapphire glass to intense impacts, as it may shatter into small fragments if, for instance, the watch falls on asphalt.
Watches with sapphire glass

"Sandwich" from different types of glass

Certain watch materials blend the strengths of the three mentioned types. For example, Saflex and Seiko's proprietary Hardlex combine the hardness of sapphire with flexibility to withstand heavy loads. Structurally, Hardlex involves a mineral base that undergoes hardening and chemical treatment, compacting the outer glass layer through ion displacement for increased durability.

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 glasses 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.

Gorilla Glass

The rapid growth of the wearable electronics market led to the incorporation of Corning Gorilla Glass, renowned for its success in smartphones, into smartwatches. These glasses are thin yet robust, effectively resisting scratches. The latest Gorilla Glass generations closely match the properties of sapphire. Specifically designed for wearables, Gorilla Glass SR+ ensures outstanding strength, optical clarity, and touch sensitivity.

Corning manufactures screen protectors for most current smartphones, some laptops and smartwatches.

While classic wrist chronographs do not use Gorilla Glass, various generations of this material are widely employed in smartwatches and bracelets. This combination offers a balance of affordability and reliability. Unlike smartphones, where a shattered screen is common, the smaller screen area of wearable devices minimizes this issue.

Good luck with your choice!