Toughened glasses are three to seven times stronger than annealed glasses. Because of safety and strength, toughened glass is used in a variety of demanding applications. Toughened or tempered glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass.

Applications in the following fields:

Automobile: Cars, trucks, Industry buses, tempos etc.
Railways: Coaches
Defense: Fleets, vehicles factory
Commercial: Hotels, shops, complex
Air ports: Doors

Used for:

Frameless glass Doors
Sliding Doors
Automatic Doors

Tempering puts the outer surfaces into compression and the inner surfaces into tension. Such stresses cause the glass, when broken, to crumble into small granular chunks instead of splintering into jagged shards as plate glass (a.k.a. annealed glass) does. The granular chunks are less likely to cause injury.
As a result of its safety and strength, toughened glass is used in a variety of demanding applications, including passenger vehicle windows, shower doors, architectural glass doors and tables, refrigerator trays, mobile screen protectors, as a component of bulletproof glass, for diving masks, and various types of plates and cookware.
Toughened or tempered glass is glass that has undergone processes of controlled thermal treatment to increase its strength.
Toughened glass is made from annealed glass that has been heated to approximately 650?C and then rapidly cooled. Due to the increased heat treatment and rapid cooling of the glass, especially between the surface and the inside of the glass, the treatment produces different physical properties. This results in compressive stress on the surface and improved bending strength of glass.
Before toughening, the glass must be cut to size or pressed to shape. This is because once it is toughened, it cannot be re-worked on. Toughened glass is widely used in a number of applications.
Toughened glass acquires a degree of strength for excess of the strength of normal glass sheet or plate glass, which if broken shatters into small and comparatively harmless pieces. It is claimed that the resistance to mechanical stock of toughened plate glass is 4 to 5 times more than that of ordinary plate glass. A toughened glass has better resistance to the vibration, mechanical shock and abrasion.

Toughened Glass has to pass the following important tests:

i. Transfer strength test on sheets on simply supplied (Modules of rupture and electricity)
ii. Impact test: By following weight on sheets supported on two wooden battens
iii. Impact by falling weight on sheet evenly bedded (on putty)
iv. Impact by falling weight on edge of sheet
v. Repeated twisting tests
vi. Sand blast abrasion
vii. Thermal tests

Because of the strength and other specific physical properties mentioned above, it finds


Toughened glass is physically and thermally stronger than regular glass.[1] The greater contraction of the inner layer during manufacturing induces compressive stresses in the surface of the glass balanced by tensile stresses in the body of the glass. For glass to be considered toughened, this compressive stress on the surface of the glass should be a minimum of 69 megapascals (10,000 psi). For it to be considered safety glass, the surface compressive stress should exceed 100 megapascals (15,000 psi). The greater the surface stress, the smaller the glass particles will be when broken.
It is this compressive stress that gives the toughened glass increased strength. This is because any surface flaws tend to be pressed closed by the retained compressive forces, while the core layer remains relatively free of the defects which could cause a crack to begin.
Any cutting or grinding must be done prior to tempering. Cutting, grinding, and sharp impacts after tempering will cause the glass to fracture.
The strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses.
Toughened glass is four to five times stronger than annealed glass of the same size and thickness against impact. Toughened glass has higher thermal strength and can withstand a high temperature differential up to 250°C.Toughened glass is considered as safety glass. It is difficult to break and even in the event of a breakage, disintegrates into small globules, which are relatively harmless.
Toughening does not alter the basic characteristics of glass such as light transmission and solar radiant heat properties.
After heat treatment, the surface of toughened glass has the same resistance to surface damage as annealed glass. Toughened glass cannot be cut, drilled or altered.
Heat soak test is recommended to be carried out on Toughened glass that is used for overhead and horizontal application, to prevent the spontaneous breakage caused due to nickel sulphide inclusion.


Toughened glass is used when strength, thermal resistance, and safety are important considerations.


The most commonly encountered tempered glass is that used for side and rear windows in automobiles. It is used for its characteristic of shattering into small cubes rather than large shards and is sometimes referred to as safety glass in this context. (The windscreen or windshield is instead made of laminated glass, which will not shatter when broken.

Buildings and structures

Toughened glass is also used in buildings for unframed assemblies (such as frameless glass doors), structurally loaded applications, and any other application that would become dangerous in the event of human impact. Tempered and heat strengthened glass can be three to seven times stronger than annealed glass. Building codes in the United States require tempered or laminated glass in several situations including some skylights, near doorways and stairways, large windows, windows which extend close to floor level, sliding doors, elevators, fire department access panels, and near swimming pools.

Household Uses

Tempered glass is also used in the home. Some common household furniture and appliances that use tempered glass are frameless shower doors, glass table tops, replacement glass, glass shelves, cabinet glass and glass for fireplaces.
“Rim-tempered” indicates that a limited area, such as the rim of the glass or plate, is tempered and is popular in food service. However, there are also specialist manufacturers that offer a fully tempered/toughened drinkware solution that can bring increased benefits in the form of strength and thermal shock resistance. In some countries these products are specified in venues that require increased performance levels or have a requirement for a safer glass due to intense usage.
Tempered glass has also seen increased usage in bars and pubs, particularly in the United Kingdom and Australia, to prevent broken glass being used as a weapon.

Cooking and baking

Some forms of tempered glass are used for cooking and baking.


Toughened glass can be made from annealed glass via a thermal tempering process. The glass is placed onto a roller table, taking it through a furnace that heats it well above its transition temperature of 564 °C (1,047 °F) to around 620 °C (1,148 °F). The glass is then rapidly cooled with forced air drafts while the inner portion remains free to flow for a short time.
An alternative chemical toughening process involves forcing a surface layer of glass at least 0.1 mm thick into compression by ion exchange of the sodium ions in the glass surface with potassium ions (which are 30% larger), by immersion of the glass into a bath of molten potassium nitrate. Chemical toughening results in increased toughness compared with thermal toughening and can be applied to glass objects of complex shapes.


The term “toughened glass” is generally used to describe fully tempered glass but is sometimes used to describe heat-strengthened glass as both types undergo a thermal “toughening” process.
There are two main types of heat-treated glass:
Heat-strengthened and fully tempered.
Heat-strengthened glass is twice as strong as annealed glass while fully tempered glass typically has four to six times the strength of annealed glass, and with stands heating in microwave ovens. The difference is the residual stress in the edge and glass surface. Fully tempered glass in the US is generally rated above 65 megapascals (9,400 psi) in pressure-resistance, while heat-strengthened glass is between 40 and 55 megapascals (5,800 and 8,000 psi).
The tempering process does not change the stiffness of the glass. Annealed glass undergoes a similar deflection compared to tempered glass under the same load, but tempered glass can take a higher load and, therefore, deflects further before breaking.