As the borosilicate fire-resistant glass has a high softening point and very low coefficient of thermal expansion, it creates a big challenge to tempering process. While the process needs to maintain the flatness of the glass sheet, it also has to ensure the tempering stress and granularity.
Usually the tensile stress in the body of the glass is proportional to the surface compressive stress. The larger the surface compressive stresses of the fire-resistant glass, the greater the internal tensile stress. The larger the tensile stress per unit area, the easier the glass to explode. To reduce the possibility of self-explosion, it must mitigate the tensile stress that the edges are exposed to while increasing the surface compressive stress.