Tempered glass has long been used in industry, construction, automotive, etc., as it is highly strong. For the last decade, tempered glass has also been used in the manufacture of mobile electronics – for smartphones, tablets, smart clocks, etc. In this article, we will talk about what tempered glass is, consider its types, features, and characteristics.
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Tempering process and properties of tempered glass
Tempered glass is an ordinary glass that has undergone a type of heat treatment – tempering. Tempering is performed by heating the glass to a temperature of 680 degrees Celsius, after which the glass is quickly and uniformly cooled by cold air. Once the treatment is complete, residual mechanical compression stresses appear on the upper layers of the glass, which gives the material additional properties compared to ordinary glass:
- Increased resistance to mechanical impact. On impact or compression, the glass absorbs more mechanical energy without breaking down.
- Resistance to temperature fluctuations. Changes in ambient temperature do not cause cracking and destruction.
- Improved safety when glass breaks. Broken glass breaks down to pieces with blunt edges, reducing the risk of damage to people in the vicinity.
After tempering, the impact strength of the glass increases by up to 5 times. The bending resistance is up to 10 times. And the tensile strength is up to 6 times.
One of the disadvantages of safety glass is the difficulty in installing it. Particularly when installing the safety glass, air bubbles may appear. To solve this problem, read how to remove air bubbles from the screen protector.
Recently, hardened glass has been treated with an oleophobic coating that improves slip resistance and scratch resistance.
Chemically strengthened glass
Besides thermal tempering of glass, there is a method of hardening glass by chemical treatment. For this purpose, the glass is placed in a potassium salt solution heated to 300 degrees Celsius. Sodium ions on the glass surface are replaced in a crystal lattice by potassium ions. And since the radius of potassium ions is larger, compression forces are formed on the glass surface, resulting in increased strength of the glass.
Chemically strengthened glass can be cut and processed without cracks or destruction. Its strength is 6-8 times higher compared to ordinary glass. The most well-known brand of chemically hardened glass is Gorilla Glass from Corning.
Read also how to clean tempered glass screen protector.
Alternatives to tempered glass
Recently, a liquid screen protector has appeared on the market. Sellers advertise it as 100% protection for your device from bumps and scratches. In our article, we have told about the advantages and disadvantages of liquid screen protectors in comparison with PET/TPU films and tempered glass. Read also about the hydrogel screen protector.
Types of tempered glass
Below you can find the most famous and common types of tempered glass. Recall that there are different types of screen defenders and each with its own advantages and disadvantages. You can also read our research on what screen protector will be the best for your phone.
Corning Gorilla Glass
It’s chemically tempered glass. The technology is regularly improved, and every new generation of Gorilla Glass is stronger than the previous one. Hardness on the Mohs scale is 5-7.
This is a less popular and widespread analog of Gorilla Glass with a comparable hardness on the Mohs scale – 5-7. The production process consists of placing glass in a hot tin furnace for hardening.
This is another type of chemically treated glass obtained through ion exchange. As in the case of Gorilla Glass, sodium ions are replaced by potassium ions.
It’s made of quartz sand. Hardness on the Mohs scale – H7. Hardened mineral glass visually resembles the sapphire one. But the hardness of tempered mineral glass is inferior to its chemically treated counterparts, which is why mineral glass is used mainly in wristwatches.
Thermally tempered glass
This is an ordinary mineral melt glass with subsequent heat treatment. This type of tempered glass is widely used as a screen protector for smartphone screens and tablets. The presence of an additional layer of glass increases its strength and reduces the risk of screen damage.
Its hardness on the Mohs scale is the penultimate and has an H9 value. This usually indicates on the packaging. But in reality, the strength of most safety glasses is within 4-7 on the Mohs scale.
Protective multilayer or armored glass
This screen protector is a combination of several glasses glued with a polymer film. This ensures that the glass does not break but is tightly held in place by the film on all sides. This technology improves the strength of the glass. Such protective glass is available in the form of overlays on the screen of mobile devices.
This is tempered glass with a natural or synthetic mineral content of sapphire. This glass is highly resistant to scratches and impacts, exceeding Gorilla Glass’ capabilities by 25%. The hardness of the Mohs scale is H9. Most often, under the name of sapphire glass is sold ordinary tempered glass with sapphire spraying.
The article describes in detail what tempered glass is. In comparison with ordinary glass, the thermal or chemical treatment of hardened glass increases its strength. Tempered glass is harder to scratch and break. At the same time, any glass has a strength advantage and weak points such as corners and ends.
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