Why Half Grid Is Often Recommended for 4mm Tempered Glass Production

When producing 4mm tempered glass, one question often comes up:

Why not just load the furnace with a full grid arrangement?

The answer lies in three key factors: heat distribution, quenching uniformity, and edge stress control.

1. Thin glass heats up faster and is more sensitive to temperature differences
Four-millimeter glass is relatively thin compared to thicker architectural glass. It absorbs heat quickly, but it also cools down quickly. If the sheets are placed too close together in a full grid, heat cannot escape evenly between the glass edges. This can cause local overheating, uneven softening, and eventually waviness or distortion.

2. A half grid improves heat transfer between sheets
In a half grid arrangement, glass sheets are spaced apart or arranged in a staggered pattern. This allows hot air to flow more uniformly around each sheet. As a result, the glass surface reaches a more consistent temperature during heating. This is especially important for thin glass, where even small temperature differences can affect flatness.

3. Better quenching effect after heating
After leaving the furnace, the glass enters the quenching section, where high-pressure air rapidly cools the surface. If the sheets are too close together, air circulation between them becomes limited. A half grid layout helps the cooling air reach both sides and edges of each glass sheet more effectively. This supports more uniform stress formation and improves the overall tempering quality.

4. Reduced risk of breaking during production
For 4mm glass, thermal stress and mechanical stress can build up quickly. Poor loading arrangement may increase the risk of spontaneous breakage inside the furnace or during quenching. By using a half grid, manufacturers can reduce edge-to-edge contact, improve airflow, and lower the chance of sheets sticking, cracking, or breaking.

Conclusion
A full grid may seem more efficient in terms of loading density, but for 4mm tempered glass, quality often depends more on uniform heating and uniform cooling.

That is why many experienced technicians prefer a half grid arrangement for thin glass:

less distortion, more consistent quenching, better stress distribution, and lower production loss.