The phenomenon in which glass breaks spontaneously is known as the spontaneous breakage of glass. This breakage happens only in tempered glass or toughened glass. The most common causes of the spontaneous breakage of glass are –
- Spontaneous breakage can happen due to mishandling or edge chipping of the glass at site.
- In some cases when toughened glass is used for external cladding, high wind loads could create a pressure and thermal stress in the glass. Sometimes the glass thickness may be very less compared to the ratio of wind loads which results in damage to the glass.
- Buildings are subject to various building movements; any such movement could create an imbalance, create internal stresses and cause the glass to break.
- Presence of small portions of nickel sulphide in the toughened glass which might grow and expand when the glass is exposed to sunlight is one of the prime reasons of the spontaneous breakage of glass.
In Spontaneous breakage, the crack happens at the stress point and then the crack expands outwards like the web. The glass is still in place when cracked but too much of external force might cause it to break. In many high rises Toughened glass is replaced with Heat strengthened glass.