What is tempered glass, toughened glass?

Tempered glass or toughened glass is a type of safety glazing material. To improve the strength of the glass, we use chemical or physical methods to form compressive stress on the surface of the glass. When an external force is subject to the glass, the surface stress is the first offset. Thus, it increases the bearing capacity and enhances the glass wind pressure resistance, cold, hot, shock, etc. It is widely used in construction, home appliances, automobiles, and other industry fields.

How to make it?

To make a toughened glass, we need to cut the float glass to the required size first. Then heat the glass close to the softening point and performing rapid and uniform cooling. After tempering, the surface of the glass forms consistent compressive stress. As a result, tensile stress creates inside. It improves the glass’s bending and impact strength, making it three to five times that of regular glass.

What are the advantages of toughened glass?


When an external force damages the glass, the fragments will become obtuse-angled small particles, which are not easy to cause serious harm to the human body.

High Strength

The impact strength of tempered glass of the same thickness is 3 to 5 times that of ordinary glass, and the bending power is 3 to 5 times that of regular glass.

Thermal stability

Toughened glass has good thermal stability, can withstand a temperature difference of 3 times that of ordinary glass, and fight a temperature of 300 ℃. Moreover, it has a noticeable effect on preventing thermal explosions.

What are the disadvantages of tempered glass?

The toughened glass cannot be subjected to any cutting, grinding, or other processing or be damaged. Otherwise, the glass will break due to the destruction of the uniform compressive stress balance.

The toughened glass can still shatter, and it has a self-exploding rate.

Why toughened glass self-explodes?

As we know the tempered glass has the possibility of self-exploding, But why? It is because the glass raw material contains nickel sulfide crystals. This kind of nickel sulfide crystal has two forms, A form and B form. Under certain time and temperature conditions, the A form will change to the B form. And the volume of the B form is 3-5 times the volume of the A form.

tempered glass explode

So although the volume of this crystal is minimal, if it becomes B-shape, the increase in volume will affect the internal compressive stress balance of the whole glass piece and cause it to break. Unfortunately, it can’t avoid tempered glass self-exploding completely under the current technology. The exploding range of regular toughened glass is 3/1000 to 5/1000.

How to reduce toughened glass self-explode rate?

To prevent the tempered glass from exploding, the heat soaking process is the best way now. After the glass is tempered, we can send it into a furnace at 300°C for about 8 hours. It simulates extreme environmental factors so that the glass spontaneously explodes in advance, which can be understood as detonation treatment. Then now, the self-explosion rate of toughened glass is 1/1000.

VSOM tempered glass Heating Soaking

Furthermore, if use ultra-clear float glass to produce the tempered glass. We can use chemical substitution reactions to eliminate the nickel sulfide impurity inside the glass when the glass is produced. As a result, the self-explosion rate of this glass after tempering is 1/100000.

In addition, we can stick the explosion-proof films on the glass to prevent the hazard.

How many types of toughened glass?

Sort by different shapes; there are flat type and curved type.

Sort by different manufacturing processes, there are physically tempered processing glass and chemically tempered processing glass. The chemical costs far more than physical ways, so it’s not widely used.

Sort by the degree of toughness, there are toughened glass ( tempering degree 2N/cm- 4N/cm, curtain wall surface stress α≥95Mpa); semi-tempered glass (tempering degree 2N/cm, curtain wall surface stress 24Mpa≤α≤69Mpa); and super tough tempered glass (tempering degree>4N/cm).

What pays attention to during tempered glass manufacturing?

The specification standard of tempered glass divides into several categories: size, appearance, safety performance, and general performance.

The safety-related items are surface stress values, fragmentation state, impact resistance, heat resistance impact performance, etc. As long as the tempering fan air pressure and the air volume are in the designed range, it can produce safety performance qualified tempered glass.

Defects that often occur in the tempering process are the curvature of the tempered glass, the bow curvature, and waveform curvature.

Firstly, the bow curvature prevents by adjusting the tempering equipment’s furnace temperature, the fan’s height, air volume distribution, etc.

Then, the most challenging thing to control in tempered glass manufacturing is the curvature of the wave near the edge, also known as wave deformation. Significantly, the waveform deformation of the temperable Low-E glass is more prominent. The waveform deformation directly affects the appearance of the building. It has a significant influence on the formation of the building curtain wall. Therefore, it tests the level of tempered glass manufacturers.

What kind of product can use toughened glass?

Toughened glass is a safety glass with high strength, which makes it widely used in different products.

For example, it can make doors, windows, railing systems, curtain walls, interior decoration, etc., in the building industry.

As for furniture manufacturing, it can make glass tables, accessories, etc. Moreover, it makes TV, oven, mobile phones, and other digital products. And also automobile window glass, military glass, etc.

tempered glass stairs