Heating temperature and heating time are the two major factors in the heating process of the glass tempering furnace. The settings of these factors are very important during tempered glass heating and they are also interrelated. If a higher heating temperature is selected, the heating time should be reduced accordingly and vice versa. 

The glass heating process is actually a transition process of glass from a brittle state to a plastic state during which the glass internal stress vanishes. 

Either too high or too low temperature in the heating furnace will lead to unfavorable results. Theoretically, a high-temperature short-time approach should be taken as far as possible to prevent the glass from deformation in the tempering furnace as a result of prolonged heating time. 

It should be noted that the glass may be deformed if the heating temperature is too high, exceeding the softening point of the glass. On the other hand, too low heating temperature will not be able to heat the glass to the tempering temperature, resulting in insufficient tempered strength, even spontaneous breakage of tempered glass in the furnace during quenching process.