Safety and Security
Safety glass is glass with additional safety features that make it less likely to break, or less likely to pose a threat when broken.
Common designs include toughened glass (also known as tempered glass), laminated glass and wire mesh glass (also known as wired glass).
Toughened glass is processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering, by design, creates balanced internal stresses which causes the glass sheet, when broken, to crumble into small granular chunks of similar size and shape instead of splintering into random, jagged shards. The granular chunks are less likely to cause injury.
As a result of its safety and strength, tempered glass is used in a variety of demanding applications, including passenger vehicle windows, shower doors, architectural glass doors and tables, refrigerator trays, as a component of bulletproof glass, for diving masks, and various types of plates and cookware.
Laminated glass is composed layers of glass and plastic held together by an inner layer membrane. When laminated glass is broken, it is held in place by the membrane between its two or more layers of glass, which crumble into small pieces. The membrane keeps the layers of glass bonded even when broken, and its toughening prevents the glass from breaking up into large sharp pieces. This produces a characteristic “spider web” cracking pattern when the impact is not enough to completely pierce the glass.
Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered. It is often used in exterior storefronts, curtain walls and windows. Skylight glazing and automobile windshields typically use laminated glass. The PVB interlayer also gives the glass a much higher sound insulation rating, due to the damping effect, and also blocks most of the incoming UV radiation.
Wire glass is a common sight in schools, businesses, and hotels across the nation. It is manufactured primarily as a fire retardant, with wire mesh inlaid in the glass to prevent it from shattering and breaking out under stress or when exposed to high temperatures.