All float glass contains some level of microscopic impurities. One type of such impurity
is nickel sulfide (NiS) inclusion. Most NiS inclusions are stable and cause no problems
but there is the potential that NiS inclusions could cause spontaneous breakage in fully
tempered glass, which brings risks and replacement costs.
Heat soaking process involves placing fully tempered glass inside a chamber and raising
the temperature to approximately 290°C to accelerate the nickel sulfide expansion.
During this process glass containing nickel sulfide inclusions will break, thus reducing
the risk of potential breakage in the field, the shattering proof process is used for
high requirement projects.
