Pre-firing is a process used in the manufacture of automotive glass. It involves applying a layer of enamel to the glass surface and then firing it at a low temperature to partially cure the enamel. The purpose of this process is to prepare the glass for subsequent processing, such as bending or laminating, without compromising the integrity of the enamel layer.

During the pre-firing process, the glass is heated to a temperature range of 550-630°C (1022-1166°F) for a period of 1-5 minutes, depending on the type and thickness of the glass. This temperature range is lower than that used for sag bending, as pre-firing is designed to partially cure the enamel layer, not fully bend the glass.

The enamel used in pre-firing is typically a black glass enamel, applied using the screen printing method. This enamel helps to block out unwanted light and reduce reflections, improving the overall appearance of the glass.

It is important to note that pre-firing should be performed by skilled technicians using specialized equipment to ensure consistent and reliable results. The use of high-quality enamel and precise control of temperature and firing time are critical to the success of the pre-firing process.

In conclusion, pre-firing is a crucial step in the production of automotive glass, providing a foundation for subsequent processing and improving the final appearance of the glass.