Process
How laminated safety glass is made
Laminated glass is made by assembling glass plies with a PVB interlayer in a clean, humidity-controlled room, de-airing the assembly under heat and pressure to form a pre-bond, then curing it in an autoclave at approximately 140 °C and 12 bar. The result is a permanent optical bond.
Lamination looks simple in outline — glass, film, glass, heat, pressure — and it is unforgiving in practice. Almost every defect in finished laminated glass traces back to something that happened before the autoclave door closed.
The lamination process, step by step
Common defects and their usual cause
| Defect | Most likely cause |
|---|---|
| Bubbles across the panel | Pressure released before the load cooled, or incomplete de-airing |
| Edge delamination | Interlayer moisture content too high, or exposed edges in service |
| Visible inclusions | Particle contamination during lay-up — a clean room issue |
| Cloudy or hazy appearance | Excessive interlayer moisture, or insufficient autoclave temperature |
| Optical distortion | Roller wave in toughened plies, or insufficient interlayer thickness for the surface deviation |
| Poor fragment retention on test | Adhesion outside the target band — usually interlayer conditioning |
Frequently asked questions
What temperature and pressure does the autoclave run at?
Typically around 140 °C at approximately 12 bar, with the exact cycle depending on interlayer type, total thickness and glass build-up. Follow the interlayer supplier's recommended cycle rather than a generic profile.
Can laminated glass be made without an autoclave?
Not with PVB. Autoclave-free lamination requires EVA, which cures with heat and vacuum alone. This is why smaller processors and decorative glass specialists often work in EVA rather than investing in autoclave capacity.
How long does a lamination cycle take?
A full autoclave cycle including heat-up, hold and controlled cooling typically runs several hours. The cooling phase cannot be rushed — releasing pressure before the load has cooled is a principal cause of bubble defects.