Heat soaking is an extra process carried out on toughened glass with Nichol Sulphide (NiS) inclusions to reduce the risk of sudden breakage
Float glass usually contains slight imperfections such as nickel sulphide (NiS) inclusions. Generally, NiS inclusions cause no problems, but on some rare occasions, Nis may lead to sudden breakage in the toughened glass without applying thermal stress or load.
Heat soaking helps identify potential causes of spontaneous breakage and address the issue. This test simulates real-time glazing conditions. It is recommended for safety-critical work like balustrades and atrium glazing, including high trafficked areas such as airports and overhead glazing. Areas with high profile projects where the risk of breakage has a significant adverse effect also require heat soak testing.
Heat soak testing is carried out to identify any NiS inclusions in toughened glass. It involves placing glass in a sealed chamber and raising the temperature. This increases nickel sulphide expansions, resulting in the breakage of any glass containing NiS inclusions in the heat soak chamber.
Identifying the inclusions during the heat soak testing can significantly reduce the breakage risks after installation. The heat soak test is a destructive process designed to break high-risk glass, generally increasing the conversion rate to 90 – 95%. Heat soaking detects NiS but doesn’t detect silica which also causes breakage.
The testing professional will position single toughened glass on special racks, place it within a calibrated oven, and then heat in a controlled manner until the last glass piece reaches 250oC. The next step is to hold the glass at 260oC ± 100C for at least two hours and then cool the glass in a controlled environment to reduce the risk of glass breakage resulting from thermal shock. Any breakage during the process is replaced before re-running the sequence again.
Heat soak testing for toughened glass aims to reduce the risk of spontaneous breakage, which helps keep you safe. At SG Commercial Glaziers, we supply and install heat soaked toughed glass.
You can contact us today on 020 3475 3078 for more enquiries on heat soaked toughed glass.