Tempered glass

Tempered glass in a squash court

The strong choice

Fully tempered glass is four to five times stronger than annealed glass, and breaks into dull-edged particles that are less likely to cause serious injury, such that tempered glass can satisfy safety glazing requirements. The higher strength of tempered glass is advantageous in point-supported and other specialty applications.

How it's made

Tempering involves heating annealed glass to over 1,000 degrees F, then rapidly cooling the glass surfaces to create permanent compressive stress.

Manage moderate thermal stress

Heat-strengthened glass can be advantageous in vision glazing applications that do not require the surface compression of fully tempered glass. In the event of breakage, heat-strengthened glass breaks into larger shards, similar to annealed glass. When heat-strengthened glass breaks, it is more likely than fully tempered glass to be retained within its framing system.

Reduce the risk of spontaneous breakage

Heat-soaked glass significantly reduces the risk of breakage caused by nickel sulfide (NiS) inclusions. While very rare, the risk of NiS cannot be eliminated from the float glass process. Due to the high surface compression of fully tempered glass, NiS inclusions can cause spontaneous breakage. The heat-soaking process helps to cause NiS inclusions to change size and break during the process, rather than after installation.

Guardian SunGuard® coated glass can be safely heat-soaked if it is determined the heat-soaking process is necessary. Explore our SunGuard coated glass below.

Improve security, safety and comfort

Guardian tempered glass can be combined with numerous ClimaGuard® residential glass and SunGuard® coated glass solutions.

Guardian Glass - ClimaGuard - 80/70 - man and daughter playing

ClimaGuard 80/70

ENERGY STAR® Northern Zone

Selectively lets visible light in to brighten and warm northern homes naturally, and provides insulation to stop heat from escaping

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Guardian Glass - ClimaGuard - 72/57 - man listing to music, snowy landscape and mountain outside window

ClimaGuard 72/57

ENERGY STAR® Northern and North-Central Zones

Provides ample light, solar heat gain and retains heat indoors in climates with cold winters

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Guardian Glass - ClimaGuard - 53/23 - photo of young African America woman reading on sofa with glass of juice

ClimaGuard 53/23

South-Central and Southern ENERGY STAR® Zones

Cools homes in warm, southern climates with triple silver protection to lower solar heat gain and U-value

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Guardian Glass - ClimaGuard - IS-20 - a group of friends playing a game

ClimaGuard IS-20


Enhances performance by lowering U-value of standard low-E windows to help meet energy codes

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Guardian Glass SunGuard - Hearst Corporation building


High-performance architectural glass that helps architects and designers Build With Light®.

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SunGuard Select Fabricators

SunGuard Advanced Architectural Glass is designed so it can be tempered by our network of independent SunGuard Select Fabricators. Our fabricators can help heat treat glass more quickly and closer to your project site for faster replacements and shorter lead times.