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.
ImageGlass panels loaded on a rack inside an industrial autoclave chamber
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
- 01
Prepare and wash the glass
Cut, edge-work and wash the glass plies, then dry them fully. Any residue, moisture or particle trapped at this stage becomes a permanent visible defect in the finished laminate.
- 02
Condition the interlayer
Bring the PVB to line conditions before opening the sealed pack — typically 15–25 °C at 20–30% relative humidity. Moisture content directly governs bond quality.
- 03
Assemble in a clean room
Lay up glass, interlayer and glass in a humidity-controlled clean room. Trim the interlayer with a small overhang beyond the glass edge to allow for flow during processing.
- 04
De-air the assembly
Remove air from between the layers using nip rollers or a vacuum bag, with heat applied. This produces a pre-bond — the assembly is now handleable and visibly clear at the edges.
- 05
Run the autoclave cycle
Cure at approximately 140 °C and 12 bar. Heat and pressure together dissolve residual air into the interlayer and complete the chemical bond to the glass surface.
- 06
Cool under pressure
Cool the load before releasing pressure. Releasing early allows dissolved air to come back out of solution and form bubbles in the finished laminate.
- 07
Inspect and trim
Trim the interlayer overhang flush with the glass edge, then inspect for bubbles, delamination, inclusions and edge defects before release.
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.