Normal toughened safety glass can be affected by something known as Nickel Sulphide Inclusion. This impurity within the tempered glass panel can cause spontaneous breakage of glass units from months to years after the installation is finished.
This spontaneous breakage post construction can obviously cause issues and extra costs on a build where glass panels need to be replaced and reinstating any building finishes after replacement.
Heat Soaked Glass is a safety glass that has a lower chance of Nickel Sulphide Inclusion being present in a glass unit and can reduce the risk of spontaneous breakage by up to 95%.
A Nickel Sulphide Inclusion is a small imperfection found in all glass manufactured that occurs due to the high levels of nickel based materials in the manufacturing process of standard float glass, such as stainless steel.
These additions can be present in any form of glass but do not cause much of an issue within normal annealed glasses due to the slow cooling times in the annealing process. Here the nickel sulphide inclusion has time to expand from its heated state to its cooled state in conjunction with the glass.
In the tempering process these cooling times are much faster to create the needed tensions within the glass. Here the nickel sulphide inclusion does not have time to fully cool and expand. This expansion then happens over the next few months or years, and the impurity can expand by up to 4%.
This expansion can cause these so called spontaneous breakages within a glass panel years after install.
Heat Soaking a glass unit involves placing the tempered glass units into a further oven after the toughening process is finished, heating and cooling the glass units in order to force any glass panels containing Nickel Sulphide Inclusions to break within the oven, rather than on site.