According to Mr. Salah Al-Otaibi, General Manager of ZGI, Heat Soak Testing is a quality control process, which guards against spontaneous breakage 'NiS inclusions are invisible to the naked eye and can form during the tempering process. Such particles freeze in an unstable form and can return to their original state, which can happen either in days, months or years due to the low temperature state at any time. If NiS particles occur within the tensile portion of the tempered glass, they increase in volume, causing fractures or breakages in the glass.'
The purpose of Heat Soak Testing is to eliminate tempered glass lites containing critical NiS inclusions, by speeding the rate of the reverse transition to the low temperature state. This means that tempered glass lites containing NiS inclusions will fracture during the heat soak process thereby eliminating the possibility of finished glass that could break in the future.
As a responsible leading glass processor, Zamil Glass Industries advocates, advises and recommends the Heat Soak Test for all architectural glass products as well as guaranteeing all of its Heat Soak Tested glasses against spontaneous breakage.