Tempering process increases the strength of glass many folds, offering a greater resistance to breakage. However, the raw materials used in the manufacturing of tempered glass are not free from certain defects namely Nickel Sulfide inclusions, which put tempered glass at potential risk of spontaneous breakage. The amount and size of these inclusions vary from glass to glass.
NiS inclusions change their structure & volume during the heating process of tempering. This changed state is ‘trapped’ during the quenching process. So at room temperature, the NiS inclusions tend to change back to their original state, which having bigger volume, cause spontaneous breakage.
This changing back of state could happen in a few minutes to a few years, making it unpredictable when tempered glass may break.
At RAMESHWARAM GROUPS, we realize the implications of spontaneous Tempered glass fracture and the much inconvenience caused. Therefore the concept of heat soaking is defined as the transfer of potential onsite breakage to breakage in the factory under a controlled process of accelerating the inversion of the nickel sulfide inclusions to their low temperature phase. In all probability, the glasses that have NiS inclusions, will break during this heat soaking process.
While heat soaking does not guarantee, that breakage will be completely eliminated in installed tempered glass, which reduces the chances drastically. Studies have been conducted world-wide indicating the reliability of heat soak test to as high as 98.5%.
All fully tempered as well as heat strengthened glasses for a project can be heat soaked in our heat soak oven.