Can a tempered glass break?

Breakage of some tempered glass sheets may occur in the absence of obvious causes due to inclusions of nickel sulfide during the float glass manufacturing process.

The HST – Heat Soak Test furnace was introduced to offer customers greater guarantees of quality because it significantly reduces the risk of spontaneous breakage of the tempered glass.

The test consists of three main phases.
During the first phase, the temperature inside the furnace is gradually raised to about 280°. This is followed by a temperature maintenance process that accelerates the breakage of the tempered glass panels with the presence of Nickel Sulfide, and the subsequent final phase of cooling and discharge.