Physics and Technology
🔥Tempered Glass
Produced by heating annealed float glass to around 620–650°C and then rapidly cooling it with high-pressure air (quenching). This creates compressive stress on the surface and tensile stress in the core, making the glass four to five times stronger than ordinary annealed glass. When fractured, it breaks into small, blunt fragments rather than sharp shards, reducing injury risk.
🌡️Heat Strengthened Glass
Produced by heating annealed float glass to approximately 620–650°C, similar to tempering, but cooled at a slower rate. Surface compressive stress is lower than tempered glass but higher than annealed glass — resulting in glass about twice as strong as ordinary annealed glass. It has less optical distortion and breaks into larger fragments, advantageous in laminated applications.
International Standards
To ensure safety and reliability, Glaspedia tempered and heat strengthened glass comply with most global standards.
- USA ASTM C1048 (United States) Defines mechanical strength and fragmentation requirements for tempered and heat strengthened glass.
- EU EN 12150 (Europe) Specifies performance criteria for thermally toughened soda-lime silicate safety glass.
- EU EN 1683 (Europe) Specifies performance criteria for heat strengthened glass.
- AU/NZ AS/NZS 2208 (Australia & New Zealand) Governs tempered and heat strengthened glass under safety glazing materials.
- INTL IEC Standards (International) Govern tempered glass use in Building Integrated Photovoltaics (BIPV) applications.
Aesthetics
The tempering or heat treating process can introduce optical effects that influence design. Roller wave, bow, or warp may cause reflections to appear uneven, particularly on large façades. Anisotropy, visible as rainbow-like patterns under polarized light, results from stress distribution within the glass. While not defects, these phenomena affect visual uniformity.
Glaspedia tempered and heat strengthened glass exemplifies the balance between physics, safety, and design. Its strength and compliance with international standards make it indispensable, while careful management of optical effects ensures it remains a material of choice for modern architecture and technology.
Frequently Asked Questions
What is the difference between tempered glass and heat strengthened glass?
Tempered glass is rapidly cooled after heating, making it 4–5 times stronger than standard glass and causing it to break into small blunt fragments. Heat strengthened glass is cooled more slowly, making it about twice as strong, with less optical distortion and larger fracture fragments — preferred in laminated applications.
Why does tempered glass break into small pieces instead of sharp shards?
The rapid quenching process creates high compressive stress on the surface and tensile stress in the core. When the glass breaks, this stored energy causes it to shatter into small, blunt granular pieces rather than dangerous sharp shards, significantly reducing the risk of injury.
What international standards does Glaspedia tempered glass comply with?
Glaspedia tempered and heat strengthened glass comply with major global standards including ASTM C1048 (USA), EN 12150 and EN 1683 (Europe), AS/NZS 2208 (Australia & New Zealand), and IEC standards for BIPV applications.
What is anisotropy in tempered glass and is it a defect?
Anisotropy appears as rainbow-like or iridescent patterns visible under polarized light, caused by internal stress distribution created during the tempering process. It is not considered a manufacturing defect but a natural optical characteristic that can affect visual uniformity on large glass façades.
Is heat strengthened glass suitable for use in laminated glass applications?
Yes. Heat strengthened glass is especially well-suited for laminated applications because when fractured, it breaks into larger fragments that remain held together by the interlayer. This fragment retention behavior makes it safer and more structurally stable compared to fully tempered glass in laminated assemblies.
How does South Star minimize optical distortion in tempered glass?
South Star uses the advanced Osprey 10 Complete by LiteSentry® inspection system combined with optimized cooling processes to detect and minimize roller wave, bow, warp, and anisotropy, ensuring that heat treated glass meets both high functional performance and aesthetic standards for modern architecture.