Serving all Illinois and Wisconsin

Unlocking the Mystery: How to Tell If Glass Is Tempered

Updated: 05/31/2024

Welcome to the ultimate guide on identifying tempered glass! As tempered glass manufacturers, we at Apex Tempered Glass are excited to share our knowledge with you. Tempered glass, known for its strength and safety features, is commonly used in various applications.

However, being able to distinguish tempered glass from regular glass is important for safety and practical purposes. In this blog post, we’ll delve into the methods for determining if glass sheets are tempered to give you the knowledge to make informed decisions.

Understanding Tempered Glass and Its Uses

Understanding Tempered Glass and Its Uses

Tempered glass is a type of safety glass that undergoes a specialized thermal treatment process. This process involves heating the glass to high temperatures and then rapidly cooling it. As a result, tempered glass becomes significantly stronger than regular glass of the same thickness. Additionally, tempered glass is designed to break into small, blunt pieces rather than sharp shards to improve safety in case of breakage.

Common Applications

Tempered glass finds widespread use in various applications due to its strength and safety features. Common applications include:

  1. Automotive Industry: Tempered glass is used for car windows, windshields, and rear-view mirrors.
  2. Construction and Architecture: It’s utilized in building facades, doors, windows, and shower enclosures.
  3. Household Products: Tempered glass is found in household items such as oven doors, table tops, and refrigerator shelves.
  4. Electronics: It’s used for smartphone screens, computer monitors, and touch panels.
  5. Furniture: Tempered glass is incorporated into furniture pieces like coffee tables and display cabinets.

6 Ways to Check Tempered Glass

Our team at Apex has made it easy to discover simple yet effective methods to distinguish tempered safety glass. From visual cues to physical tests, learn how to confidently recognize this safety-enhanced material.

Method Description
Check Smooth Edges Inspect edges for smoothness. Tempered glass typically lacks sharp edges of untreated glass.
Look for Surface Imperfections Examine the surface for subtle distortions or imperfections, which are common in tempered glass.
Look at It Against the Sun Use polarized sunglasses to reveal stress patterns, indicating tempered glass.
Drill Test Attempt to drill the glass; tempered glass will resist and shatter into small pieces.
Check Stamp of Authenticity Look for a discreet stamp or identifier indicating tempered glass status.
Score a Line Score a line on the glass surface; tempered glass will resist and may shatter into small pieces.

1. Check Smooth Edges: A Sign of Tempering

Check Smooth Edges: A Sign of Tempering

Inspecting the edges of glass can unveil valuable clues about its tempering. Tempered glass boasts remarkably smooth edges, devoid of the sharp edges typically found in ordinary annealed glass. This smoothness is a result of the tempering process, where the glass undergoes intense heating and rapid cooling. So, run your fingers along the same glass edges — if they glide effortlessly without encountering any roughness, you’re likely dealing with genuinely tempered glass.

2. Look for Surface Imperfections

Look for Surface Imperfections

Take a closer look at the glass surface — imperfections tell a story. Unlike ordinary glass, tempered glass often exhibits subtle distortions or imperfections. These may manifest as slight waves or ripples, indicative of the tempering process. Keep your eyes peeled for any irregularities or anomalies on the surface — they could be the key to identifying tempered glass.

3. Look at It Against the Sun While Wearing Polarized Sunglasses

Look at It Against the Sun While Wearing Polarized Sunglasses

Don a pair of polarized glasses and step into the world of hidden stress patterns. When viewed through polarized lenses, tempered glass reveals mesmerizing stress patterns that are invisible to the naked eye.

These patterns, a result of the tempering process, manifest as intricate designs, offering undeniable proof of tempered glass. Grab your polarized glasses and embark on a visual journey to uncover the secrets within the glass.

4. Drill Test: Tempered Glass Will Shatter

4. Drill Test: Tempered Glass Will Shatter

Feeling adventurous? Put tempered glass to the test with a simple drill examination. Unlike regular glass, tempered glass resists drilling efforts, often shattering into countless small pieces upon impact. In the case that your attempt to drill leaves you with a shattered spectacle rather than a clean hole, chances are you’ve encountered tempered glass. Just remember to exercise caution and wear appropriate safety gear during this experiment.

5. Check the Stamp of Authenticity

Check the Stamp of Authenticity

Seeking definitive proof of tempered glass? Look no further than the stamp of authenticity. Many tempered glass products feature a discreet stamp or identifier, confirming their genuine tempered glass status. This stamp shows the manufacturer’s name and the CPSC (Consumer Product Safety Commission) standards. Keep an eye out for these markings — they may include codes, logos, or symbols that indicate compliance with industry standards. A quick glance at the stamp can provide reassurance of the glass’s authenticity and quality.

6. Score a Line: Identifying Tempered Glass with a Cut

Score a Line: Identifying Tempered Glass with a Cut

One straightforward method for identifying tempered glass is by scoring a line on its surface. You can use a sharp object like a glass cutter or a diamond pen to carefully score a line across the glass.

However, exercise caution and wear appropriate safety gear, such as gloves and eye protection, to avoid injury. If the glass is tempered, it’ll resist the scoring and may even shatter into small, relatively harmless pieces. In contrast, regular glass will easily score and may exhibit a clean break. This is a fast and easy method to confirm whether the glass is tempered or not.

Other Methods to Check for Tempered Glass

Beyond the straightforward techniques we’ve discussed, there are other ways to check tempered glass. However, these methods are more complex and require specialized tools and expertise.

  • Thermal Stress Test: This involves applying heat to the glass and observing its reactions. Common tools like a heat gun or a blowtorch are used for this purpose.
  • Acid Etching: Acid is applied to the glass surface to see how it reacts. Tempered glass will show a different reaction compared to untreated glass to help you identify its tempering.


As a Chicago tempered glass manufacturer proudly serving Illinois and Wisconsin, we at Apex Tempered Glass are committed to delivering premium quality products tailored to your specific needs. From custom craftsmanship to free delivery and installation, see why so many people trust us with their glass manufacturing needs.

Get in touch with us today for a free quote on custom tempered glass solutions that meet your requirements and exceed your expectations. Your safety and satisfaction are always our top priorities.

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.


Get Your Free Quote Today!

With a commitment to quality and innovation, we’re here to exceed your glass expectations. Get in touch now to discuss your project.

*We serve Illinois and Milwaukee area