Heat-strengthened glass is approximately twice as strong as annealed glass of similar thickness and configuration. Heat-strengthened glass generally fractures in a manner similar to annealed glass and tends to remain in the opening when broken. It is intended for general glazing where additional strength and/or resistance to mechanical and/or thermal stress are desired. Heat-strengthened glass is NOT a safety glazing product and therefore should not be used where safety glazing is required. Fully tempered glass is approximately four times stronger than annealed glass of the same thickness and configuration. When it is broken, tempered glass fractures into small fragments that reduce the probability of serious injury as compared to annealed glass. Tempered glass meets all safety glazing standards including the federal safety glazing standard, CPSC 16 CFR 1201. Because tempered glass fractures into many small pieces, it tends to vacate the opening, when broken, more than heat-strengthened and annealed glass does.
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Tempered & Heat Strengthened
Tempered & Heat Strengthened
Heat-treated glass can be either heat-strengthened, which is not considered safety glazing and fully tempered which is considered safety glazing.
- • Fully tempered glass meets all safety glazing standards including the federal safety glazing standard, CPSC 16 CFR 1201.
• Fully tempered glass meets all safety glazing standards including the federal safety glazing standard, CPSC 16 CFR 1201.
- Heat Strengthened Glass due to its superior glass retention properties, heat-strengthened glass is the preferred heat-treated glass product for applications where additional strength is needed to meet mechanical loads (wind or snow) or thermal loads caused by certain tinted or coated glasses. The color, chemical composition and light transmission characteristics of glass remain unchanged after the heat-treating process. The physical properties of glass, such as the compressive strength, hardness, specific gravity, the softening point, thermal conductivity, solar transmittance, stiffness and expansion coefficient, also remain unchanged. Heat-Strengthened glass is widely used in laminated glass for additional strength, such as in overhead and sloped glazing. Heat-Strengthened glass cannot be used in any safety glazing applications.
- Fully Tempered glass is used when the strength requirements exceed the capabilities of heat-strengthened glass, and for all safety glazing applications. Fully Tempered Glass is heat-treated by heating annealed glass to a temperature of approximately 1,150ºF (621°C), then rapidly cooling it. The glass is cooled by a carefully controlled airflow (also known as quenching), which uniformly cools all glass surfaces simultaneously. High airflow rates produce tempered glass and much lower airflow rates produce heat-strengthened glass. Tempered glass is commonly used in sliding doors, storm doors, atriums, partitions, windows, storefronts, display cases, bath and shower enclosures and all-glass doors and entrances. Tempered glass should not be installed in areas where it is exposed to temperatures greater than approximately 400°F because it will begin to lose its degree of temper (reverting back to annealed glass).
- Fully Tempered Capabilities
- Most architectural glass products can be heat-treated. Some patterned glass and decorative glass with a deep surface pattern may not be heat-treatable. Silk-Screened and ceramic spandrel glass are always either heat-strengthened or tempered as part of their fabrication process. When spandrel glass is incorporated into insulating glass units, both lites must be heat-treated. Heat-absorbing glasses, such as standard and high performance tints, reflective glasses and some Low-E glass, may require heat treatment to reduce the probability of thermal-stress breakage, especially when used as part of an insulating glass unit.
- Heat Strengthened Capabilities
- Most architectural glass products can be heat-treated. Some patterned glass and decorative glass with a deep surface pattern may not be heat-treatable. Silk-Screened and ceramic spandrel glass are always either heat-strengthened or tempered as part of their fabrication process. When spandrel glass is incorporated into insulating glass units, both lites must be heat-treated. Heat-absorbing glasses, such as standard and high performance tints, reflective glasses and some Low-E glass, may require heat treatment to reduce the probability of thermal-stress breakage, especially when used as part of an insulating glass unit.
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