1. When glass heating temperature exceeds the softening point, the glass can be easily deformed,  and significant damage will be caused  to the surface quality of tempered glass.

2. When the radiation temperature of the heating element gets too high, the peak value of radiation intensity will move in the direction of shortwave. The radiant-ray will penetrate the glass and not be absorbed. Because of that, the increase of the heat of this kind will be wasted.

3. If the heating temperature is too low, the small temperature gradient will slow down the relaxation speed of glass internal stress.

4. In case the heating temperature is too low, the inner side of the glass will not be fully heated in the same length of time and the residual stress not be completely released. It will affect the re-distribution of the stress after cooling. The glass also tends to break during quenching process.

5. When the heating temperature is too low, the properties of tempered glass will deteriorate and tempered glass will shatter into larger pieces.

Therefore, it is critical to set the right heating profile during glass tempering process.Temperature should be determined according to the heating properties of glass at different stages.