Light, malleable and versatile: glass is undoubtedly one of the most used materials in the furnishing sector.
In addition to the glass obtained from silica sand, which is a natural raw material, a type of glass is often produced deriving from its recycling once purified and properly treated.
This type of glass requires a particular degree of attention during the working phase: in fact, the slab that is obtained, once the recycled glass has been melted, must not present any defect that would otherwise compromise its integrity.
One of the most requested glass processing is tempering, which makes tempered glass far more valuable than non-tempered glass.
We know more about curved tempered glass
Tempered glass, ortempered glass, is the final result of a process called quenching during which the slab is inserted inside a furnace where the temperature is between 650 – 750 °.
In these thermal conditions, the slab is highly viscous and this means that the material adheres perfectly to the mold used, which can be concave or convex; the curvature is achieved either by gravity, leaving the glass paste to adhere slowly to the fixed, semi-variable or variable-configuration mold (freely configurable) placed under it, or by pressure through the crushing inside a “male” mold and of a “female” who are lowered from above and brought up from below.
The glass plate is then cooled through a series of air jets coming from different directions: the upper and lower part of the surface cool quickly while the inner part, the soul of the glass, cools more slowly causing in the following moments greater instability of the molecules and fragility of the slab.
Through the tempering process the curved tempered glass gains more elasticity and resistance to impacts and pressures.
Why we talk about safety glass
Often we refer to tempered glass with the expression: “safety glass”. In fact, in the event of breakage the tempered glass, whether flat or curved, breaks into many pieces with a rounded shape, therefore without sharp edges: in this way, the person present at the time of the break does not risk injury. On average, about 40 fragments should be obtained from a square piece of 6mm thick glass that is breaking.
It is the European standard UNI EN 12150 which establishes the quality criteria of the tempering process by determining the characteristics of tempered glass.
Comparison between classic glass and tempered glass: the differences
Classic glass and tempered glass have differences that hardly ever appear at first sight, but trying to overheat the tempered glass plate to test its strength or break it to verify that it actually breaks into blunt fragments are “extreme” tests that can be safely avoided.
In fact, there are other aspects that you should consider to identify the type of glass plate you are dealing with: let’s see them together.
The first element that distinguishes tempered glass is the laser-printed serial number, so that it cannot be eliminated, which is usually found in the corners and parts of the plate that are less visible.
Compared to classic glass, the tempered glass has a much greater thickness (about 5 times higher), completely round corners and if polarized lenses are used it is possible to see blue or black stripes inside.
Finally, looking through a tempered glass the images are distorted due to undulations due to the passage on the rollers present in the oven used for the tempering and it is also possible to notice imperfections and whitish stripes.
When and how tempered glass is used
The versatility and malleability of glass mean that tempered glass is used in different areas: from the furnishing sector, to illuminate the rooms and create an overall elegant and refined style, to the automotive one.
In the indoor sector this material is used for:
- internal partition walls, separating spaces and favoring the passage of light;
- shower enclosure, avoiding dangerous domestic accidents in case of breakage;
- shop windows;
- external walls of glass buildings.
Finally, in the automotive sector, tempered glass has until now been used in windshields; the tendency, however, is to replace it with the stratified, a type of glass made “sandwich” with layers of plastic material that cushion the blows and prevent the glass from breaking in the event of shocks.