(1) The temperature difference of the annealing furnace The distribution of the cross-sectional temperature of the general glass product annealing furnace is very uneven, the temperature near the two sides is generally lower, and the center temperature is generally higher, so that the temperature of the product is not uniform, especially the room type Annealing furnace. For this reason, when designing the annealing curve, the slow cooling rate should be lower than the actual allowable permanent stress, and generally half of the allowable stress is used for calculation. Ordinary products can take the allowable stress value of 5 to determine the heating rate and fast cooling rate, and also consider the factors affecting the temperature difference of the annealing furnace.