Process »»»

The concept of heat soaking is defined as the transfer of potential on site breakage in the factory under controlled process of accelerating the inversion of the nickel Sulphide inclusions to their low temperature phase. In all probability, the glass that has Nis inclusions will break during his heat soaking process.

Studies have been conducted worldwide indicating the reliability of heat soak test to as high 98.5%.

Gold Tuff Toughened Safety Glass and Heat Strengthened Glass can be specified Heat Soaked.
Heat Soaking is a quality control check carried out, when specified, to detect and reject any Toughened Glass that may have inclusions (Nickel Sulphide) or edge defects that may cause breakage after installation.

Nickel Sulphide (NIS) has been known to be the cause of spontaneous burst in tempered glass. During tempering the Nickel Sulfide is transformed to the high temperature alpha ---phase (T>380C) and has no time to return to thebeta- phase on quenching with the passage of time NIS slowly inverts to the low temperature beta -phase with an increase in volume of about 4%. This volume expansion may cause glass breakage.
The heat soak is a destructive treatment which heats the glass for several hours at about 290C to speed up the alpha - NIS to Beta- NIS transformation and consequently forces the contaminated glasses broken within the oven.