As a glass structural engineer, you might often face the challenge of specifying the right glass quality for high-profile facades. The key to getting the best possible or most suitable glass for your project lies in finding the right balance: overspecification can lead to suppliers declining to quote, while underspecification may result in receiving subpar materials. So, what is the best glass quality you can realistically obtain from the market?
Not every project demands the highest possible glass quality. It's more practical to focus on the most suitable glass quality for your specific needs. Industry standards like EN 12150 often have very loose criteria; glass that barely meets these standards might not be ideal for your project. Therefore, identifying the critical criteria for your project and ensuring they align with your plans is essential.
Understanding Glass Quality Criteria
The tempering and heat-strengthening processes inherently cause some deviations in the glass. The acceptability of these deviations largely depends on the glass's installation location. For high-profile facades, stringent quality requirements are necessary, whereas for interior glass, where observation distance is shorter, the criteria can be less strict.
Here are some key considerations for specifying high-quality glass in terms of surface quality:
1. Rollerwave Deviation: This measures the peak-to-valley depth of the wave on the glass surface. For top-quality glass, the rollerwave deviation should not exceed 0.08 mm.
2. Edge Lift: This measures the deviation in a 300 mm area from the edge of the glass. The peak-to-valley deviation should not exceed 0.2 mm from the leading or trailing edge.
3. Overall Bow: This measures the curvature of the glass. The maximum acceptable bow should be 1.5 mm/m, including both bow and warp.
Example Specification for 6 mm Glass
To ensure you receive top-quality glass that good processors in the market can deliver, consider using the following example specification for 6 mm glass:
Rollerwave Deviation: Maximum peak-to-valley depth of 0.08 mm.
Edge Lift: Maximum peak-to-valley deviation of 0.2 mm within 300 mm from the edge.
Overall Bow: Maximum deviation of 1.5 mm per meter, including both bow and warp.
By specifying these criteria, you can ensure that you receive high-quality glass suitable for your high-profile facade projects. This approach will help you strike the right balance between quality and feasibility, making your project a success.
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