Structural glass is created by combining multiple layers of glass, often thermally toughened, and bonding them together using heat and vacuum to achieve the necessary strength and safety.
Here's a more detailed breakdown of the process:
1. Glass Selection & Preparation
- Glass Type: The process starts with selecting the right type of glass. Common choices include:
- Float Glass: Standard annealed glass.
- Low-Iron Glass: Offers greater clarity due to reduced iron content.
- Thickness: The thickness of each glass layer is determined based on the structural requirements of the application.
- Cutting and Edging: The glass is cut to the required dimensions and the edges are processed to remove any sharp or weak points.
2. Thermal Treatment (Tempering/Heat Strengthening)
- Tempering: This process involves heating the glass to a high temperature and then rapidly cooling it. This creates a compressive stress on the surface and tensile stress inside, making the glass significantly stronger (around 4-5 times) than annealed glass. When broken, tempered glass shatters into small, relatively harmless pieces.
- Heat Strengthening: Similar to tempering, but the cooling process is slower. Heat-strengthened glass is about twice as strong as annealed glass and its breakage pattern is similar to annealed glass but with larger fragments. While not as strong as tempered glass, it offers improved resistance to thermal stress.
3. Interlayer Selection & Preparation
- Interlayer Materials: These are bonding materials placed between the glass layers. Common options include:
- Polyvinyl Butyral (PVB): A widely used interlayer that provides excellent adhesion, impact resistance, and sound dampening.
- SentryGlas® (Ionoplast): A more rigid interlayer offering superior strength, clarity, and edge stability compared to PVB. It is often used in demanding structural applications.
- Ethylene-Vinyl Acetate (EVA): Primarily used in decorative and specialty applications.
- Cutting and Cleaning: The interlayer is cut to size and carefully cleaned to ensure optimal adhesion.
4. Lamination Process
- Lay-up: The glass layers and interlayers are carefully aligned and assembled.
- De-airing (Vacuum Bagging): Air is removed from between the layers using a vacuum bag or roller system to prevent bubbles and ensure proper bonding.
- Heating & Pressing (Autoclaving): The assembled glass is placed in an autoclave, where it is subjected to high temperature and pressure. This melts the interlayer and bonds the glass layers together.
5. Quality Control
- Inspection: The laminated glass is thoroughly inspected for any defects, such as bubbles, delamination, or scratches.
- Testing: Samples may undergo testing to verify the strength, impact resistance, and optical properties of the laminated glass.
Example Applications
- Glass Floors: Multiple layers of tempered and laminated glass provide the necessary strength and safety for walkable surfaces.
- Glass Beams and Fins: Load-bearing glass elements require precise engineering and high-performance interlayers like SentryGlas® to handle structural stresses.
- Glass Facades and Curtain Walls: Laminated glass provides both structural support and weather resistance in building envelopes.
In summary, the manufacture of structural glass is a precise process combining select materials, thermal treatment, and bonding techniques to create a safe and robust building component.
