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What Is Tempered Glass? A Comprehensive Guide

Updated: 05/31/2024

Ever wondered what makes that glass on your shower door so much stronger than a drinking glass? The answer lies in a process called tempering. In this comprehensive guide by Apex Tempered Glass, we’ll delve into the world of tempered glass, exploring its creation process, unique properties, and the diverse applications that make it a ubiquitous feature in our everyday lives. From understanding its remarkable strength to discovering its various types and uses, get ready to have your knowledge of this fascinating material shattered (in a good way, of course)!

What Is Tempered Glass?

Unlike its regular glass counterpart, tempered glass undergoes a special treatment to transform into the robust material we know today. This process is called thermal tempering and involves meticulously heating the glass to extremely high temperatures, often exceeding 1000°F (538°C). Subsequently, the heated glass is rapidly cooled with powerful jets of air, creating a unique internal stress pattern. This process strengthens the glass significantly, making it several times more resistant to impact and thermal stress compared to untreated glass.

What Is Tempered Glass?

The Tempering Process: How Ordinary Glass Becomes Tempered Safety Glass

The transformation of regular glass into tempered glass is a fascinating process:

  1. Cutting and shaping: The glass is first cut and shaped according to its intended use.
  2. Heating: The glass panels are heated uniformly in a furnace to temperatures exceeding 1000°F (538°C).
  3. Rapid cooling: Once the desired temperature is reached, the glass is rapidly cooled with high-pressure air blasts. This rapid cooling creates a compression layer on the outer surfaces of the glass and a tension layer in the inner core.
  4. Quality inspection: The finished tempered glass undergoes rigorous inspection to ensure it meets safety standards and has no imperfections.

The Science Behind the Strength

The rapid cooling process creates a permanent state of compression in the outer surfaces of the glass and tension in the inner core. This internal stress distribution makes tempered glass significantly stronger and more resistant to impact.

When Tempered Glass Breaks: Understanding the Shattering Pattern

Tempered glass, when subjected to extreme force or pressure, breaks in a specific way:

  • Complete disintegration: Unlike regular glass, which shatters into large, sharp shards, tempered glass shatters completely into small, blunt fragments. These fragments are often referred to as “diced glass” or “tetragonal fragments.”
  • Rapid breakdown: The shattering happens almost instantaneously, releasing the internal stress within the glass.

Safety Through Shattering

While breaking may seem like a negative, the way tempered glass breaks is its key safety feature. The small, blunt fragments are far less likely to cause serious injuries compared to the large shards of regular glass.

Tempered Glass vs. Annealed Glass: Understanding the Difference

Annealed Glass

This is the most common type of glass used in windows, bottles, and other everyday applications. It undergoes a slow cooling process during manufacturing, making it relatively weak and prone to shattering into large, jagged shards when broken. Be careful, these shards can cause serious injuries.

Tempered Glass

Tempered glass goes through a thermal tempering process, which involves extreme heating and rapid cooling. This process creates internal stress within the glass, making it:

  • 4-5 times stronger than annealed glass of the same size and thickness.
  • Much safer when broken. It shatters into small, blunt fragments (often called “diced glass” or “tetragonal fragments”) that are less likely to cause injury.

Here’s a table summarizing the key differences:

Feature Annealed Glass Tempered Glass
Strength Weaker 4-5 times stronger
Breakage Large, sharp shards Small, blunt fragments
Safety Lower Higher
Applications Windows, bottles, mirrors Shower doors, windows, appliances

Why Choose Tempered Glass?

Why Choose Tempered Glass?

Tempered glass offers a compelling combination of strength, safety, and aesthetics. Here’s a summary of the key reasons to choose tempered glass:

  • Enhanced safety: Tempered glass significantly reduces the risk of injuries caused by broken glass due to its unique shattering pattern.
  • Increased strength: It’s several times stronger than regular glass, making it more resistant to impact and pressure.
  • Improved thermal resistance: Tempered glass can withstand higher temperatures than regular glass, making it suitable for certain applications.
  • Versatility: Tempered glass is used in various settings, from buildings and appliances to furniture and consumer products.

Where You’ll Find Tempered Glass: Applications and Uses

Tempered glass plays an important role in various applications due to its superior strength and safety features. Here are some of the most common uses:

Tempered Glass Windows

Tempered glass is often used in windows, particularly in:

  • High-traffic areas: Places with a high risk of accidental impact, like schools, hospitals, and office buildings.
  • Large windows and patio doors: Tempered glass ensures safety in case of breakage due to extreme weather events.
  • Frameless glass shower doors: Tempered glass is mandatory by building codes for shower doors due to the risk of impact and potential injury.

Glass in Buildings

You’ll also find tempered glass in:

Consumer Products

Tempered glass finds applications in various household items, including:

  • Glass table tops;
  • Oven doors;
  • Microwave doors;
  • Side windows in cars (tempered for safety but not the windshield, which is laminated glass for a different safety benefit);
  • Display cases.

Additional Considerations

  • While tempered glass is significantly stronger than regular glass, it can still break under extreme force or pressure.
  • Tempered glass, when broken, shatters completely and cannot be repaired. However, this is a safety feature, as it eliminates the risk of large, sharp shards remaining.

Tempered Glass Window Alternatives: Exploring Other Options

Tempered Glass Window Alternatives: Exploring Other Options

While tempered glass offers excellent safety benefits for windows, there are alternative options to consider depending on your needs:

  • Laminated glass: This type of glass consists of two or more glass layers bonded together with a clear plastic interlayer. Laminated glass offers superior security benefits as it’s difficult to penetrate and tends to crack but not shatter upon impact.
  • Security window films: These are transparent films applied to the inner surface of an existing window. They can add a layer of protection against shattering and forced entry. However, they don’t offer the same level of strength and safety as tempered glass.

Choosing the Right Option

The best choice for your windows depends on your unique needs. Here’s a quick guide:

  • For high-traffic areas and safety: Tempered glass is the clear winner.
  • For security against break-ins: Laminated glass or tempered glass with security film can be good options.
  • For existing windows: Security window films offer an affordable solution for adding a layer of protection.

Beyond Windows: Additional Uses and Benefits of Tempered Glass

Tempered glass offers advantages beyond just windows. Here are some additional benefits and applications:

  • Thermal shock resistance: Tempered glass can withstand sudden temperature changes better than regular glass, making it suitable for applications like oven doors.
  • Improved safety in appliances: Tempered glass is used in various appliances like microwaves and oven doors because it reduces the risk of shattering due to heat.
  • Enhanced aesthetics: Tempered glass offers a clean and modern look, making it a popular choice for furniture and display cases.

Important Note

Tempered glass cannot be cut, drilled, or altered after the tempering process. Any modifications need to be done before the tempering stage.

Finding Tempered Glass: Where to Look

Tempered glass is readily available from various sources:

  • Glass manufacturers and distributors: These companies specialize in different types of glass, including tempered glass.
  • Home improvement stores: Many home improvement stores carry pre-cut tempered glass for various applications like shelves or table tops.
  • Custom glass shops: These shops can create custom-sized tempered glass pieces based on your specific needs.


By understanding the properties and benefits of tempered glass, you can make the best decisions for your needs. While it might not be the solution for every situation, tempered glass can promote safety and create a more secure environment in homes and buildings.

Elevate your space with the confidence of Apex Tempered Glass! Located in Chicago, we’re experts in crafting high-quality tempered glass solutions. Our team is passionate and dedicated to providing custom designs to perfectly match your needs. Get a free quote today and see how we can transform your vision into reality.

Nina Tsoy

Finance And Operations

Nina leads Apex Tempered Glass, a company specializing in manufacturing all types of glass. Known for her strategic expertise and exceptional operational performance, Nina is committed to providing innovative solutions for any glass-related issue.


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