White haze  is a common optical defect in the tempering process caused by mechanical friction or improper thermal parameters. This guide outlines the root causes and corrective actions for haze appearing longitudinally (in the center) and transversely (at the ends) of the glass panel.

1. Longitudinal White Haze (Center of the Panel)

When longitudinal white haze appears along the middle of glass panels, it is typically caused by a combination of mechanical misalignment and thermal imbalances. Mechanically, the issue often stems from poor equipment leveling, radial runout in the ceramic roller bed, slipping O-shape belts, or damage to the main shaft coupling keyway. Thermally, the causes include insufficient heat balance, low temperatures in the upper convection furnace, excessive glass oscillation speed, or excessively high temperatures in the bottom of the radiation furnace.

Corrective Measures: To resolve these issues, operators must first verify the equipment's level and inspect the ceramic rollers for radial runout, ensuring the bearing seats are properly filled with high-temperature lithium lubricating grease. It is also essential to check if the O-shape belts are loose or slipping and to examine the main shaft coupling keyway for damage, initiating repairs or replacements if necessary. Regarding process parameters, operators should appropriately increase the heat balance pressure and operating time, and increase the speed of the convection blowers above the convection furnace. Simultaneously, the speed of the glass oscillation inside the furnace should be lowered, and the temperature in the lower part of the radiation furnace should be reduced to prevent overheating.

2. Transverse White Haze (Ends of the Panel)

Transverse white haze occurring at both ends of the glass is primarily driven by improper temperature profiles. Common reasons include an excessively large temperature difference between the upper and lower parts of the furnace, or the temperature in the bottom section being set too low. Specific furnace types also have unique causes: in Radiation furnaces, this defect results from excessive heat balance pressure and operating time; in JetConvection furnaces, it is caused by an excessively high rotating speed of the convection blowers in the upper part of the furnace.

Corrective Measures: To eliminate transverse haze, the temperature difference between the upper and lower furnace sections must be strictly controlled within 10℃, and the temperature in the bottom part should be appropriately increased. For Radiation furnaces, the heat balance pressure and operating time should be appropriately reduced. For JetConvection furnaces, the rotating speed of the upper convection blowers must be lowered to reduce thermal impact on the glass ends.