Because the temperature in the oven, instance swing quickly. Make a glass of liquid temperatures temperature not. And thus adversely affect the temperature of the glass.
Caused by rapidly fluctuating temperatures in the furnace. Cause the temperature of the glass trough conveyor dryer behind. Thus affect the temperature of the glass are not equal.
Caused by temperature in furnace swing rapidly. The temperature of the trough conveyor glass temperature in time. Therefore the impact to the temperature of the glass are not equal.