Quenching to form glass final stress plays a decisive role on the glass quenching of the basic requirement is that the glass is cooled uniformly cooling rate in accordance with the requirements of the glass to obtain a uniform stress distribution.

For air-cooled quenching method, the cooling rate is determined by the air pressure, air temperature, air flow rate, nozzle spacing and glass and other factors, factors beyond the control of the general production of pressure and distance between the nozzle and the glass.

Stress heated glass completely released, after entering the quenching section, cooling glass started in accordance with the rate-setting, surface temperature decreases, the surface began to volume contraction, but the center layer of glass remains higher temperature, the volume has not had time to change, then glass temporary surface tensile stress, a little inner stress generated temporarily, the center layer stress relaxation occurs. This stage is easy because the glass surface defects cause rupture. If the residual stress within the glass is not completely eliminated, tempered glass is often due to the initial stress caused by the re-construction glass crack, glass and cause of stress is not completely eliminated and more generally for glass or glass heating temperature is not enough heating time is too short, or temperature homogenized enough.

With further cooling the temperature of the glass, the glass surface temperature below the glass transition temperature drops, the glass surface hardening contraction stop, the inner layer continue to shrink, until the temperature is reduced to the glass transition temperature, the glass surface to form a compressive stress, the inner layer is formed Zhang stress. In this case the presence of stress within the glass, even if the temperature gradient disappear and can not be eliminated, permanent stress.