Serving all Illinois and Wisconsin

Unveiling the Art of Crafting Tempered Glass: A Comprehensive Guide

Updated: 05/31/2024

Tempered glass has made a fascinating journey from humble raw materials to a marvel of modern engineering. This fortified glass, renowned for its exceptional strength and resilience, undergoes a meticulous manufacturing process that transforms it from molten form to a product of unparalleled durability.

In this article, we at Apex Tempered Glass, as a tempered glass manufacturer, will uncover the intricate steps involved in crafting tempered glass and shed light on its creation and significance.

What Is Tempered Glass?

Tempered glass, also known as safety glass, is a type of glass specially treated for increased strength and safety.

Here’s a breakdown of its benefits:

  • Strength: Through a heating and rapid cooling process (tempering), tempered glass becomes several times stronger than regular glass. This makes it more resistant to impacts, blows, and even minor explosions.
  • Safety: The key benefit of tempered glass lies in its shattering pattern. Unlike regular glass that breaks into large, sharp shards, tempered glass shatters into small, blunt fragments. This significantly reduces the risk of injuries in case of breakage.
  • Heat resistance: Tempered glass can withstand higher temperatures compared to regular glass, making it ideal for applications like oven doors or kitchen backsplashes.

How Is Tempered Glass Made?

The manufacturing process of tempered glass involves several distinct steps to ensure its strength, durability, and safety. Here’s a simplified overview of the typical steps.

How Is Tempered Glass Made?

Step 1. Selection of Raw Materials

The journey to tempered glass begins with meticulous material selection. High-quality ingredients are essential to ensure the final product’s strength and clarity.

  • Base glass: Large quantities of silica sand (a primary component of glass) are used along with other minerals like soda ash, limestone, and feldspar.
  • Quality control: Strict measures are taken to remove impurities like iron, which can affect the glass’s clarity and weaken its structure.

These carefully chosen raw materials form the foundation for the transformation into robust tempered glass.

Step 2. Melting

Once the raw materials are selected and precisely measured, the transformation into molten glass begins:

  • Mixing and heating: The raw ingredients are meticulously combined in large furnaces. Intense heat, reaching up to 1500°C (2732°F), melts the mixture, transforming it into a viscous liquid.
  • Refining: High temperatures not only melt the materials but also initiate a crucial process called refining. This step eliminates any remaining gas bubbles or impurities that could compromise the glass’s structural integrity.
  • Homogeneity: Maintaining consistent temperature throughout the molten mixture is vital. This ensures the glass achieves a uniform composition and clarity, free from imperfections that might later lead to breakage during tempering.

The molten glass, now a homogenous liquid free of bubbles and impurities, becomes the canvas for the next stage: shaping into the desired form.

Step 3. Shaping

Step 3. Shaping

Step 3 deals with transforming the molten glass into its initial shape. However, it’s crucial to remember that shaping cannot be done after tempering due to the inherent properties of the process. Therefore, shaping often occurs before the tempering stage.

Here are two common shaping methods for tempered glass:

  • Float process: This dominant method involves pouring the molten glass onto a bed of molten tin. The glass floats due to its lower density, spreading evenly and forming a flat sheet with smooth surfaces. This method is ideal for creating large, uniform panels used for windows, shower doors, and architectural applications.
  • Pressing: For specific curved shapes, pressing techniques are employed. Molds are used to shape the molten glass as it solidifies. This method is suitable for smaller items requiring non-flat profiles, such as certain electronic components or decorative glass pieces.

After shaping, the glass undergoes further cooling and then continues to the crucial tempering process. This is where it gets its enhanced strength and safety features.

Step 4. Quenching (Tempering Process)

This stage is the essence of the transformation process, where regular glass gains its remarkable strength and safety features:

  • Rapid cooling: The carefully shaped glass, previously heated to around 620°C (1148°F), enters a crucial zone. Here, it’s subjected to a rapid cooling process using high-pressure jets of cool air. This rapid quenching is what differentiates tempered glass from annealed glass.
  • Uneven cooling: The key to the process lies in the uneven cooling rate between the glass’s internal core and its outer surfaces. The air jets rapidly cool the outer surfaces at a much faster pace compared to the inner core.

Internal Stress Creation

This contrasting cooling creates a unique state of internal stress within the glass:

  • Compression: The rapidly cooled outer surfaces contract, placing them in a state of compressive stress. This essentially squeezes the outer layer, making it significantly stronger.
  • Tension: The inner core, cooling at a slower pace, experiences tensile stress. This creates a pulling force within the core.

This deliberate stress distribution is the secret behind tempered glass’s exceptional properties: impact resistance and thermal shock resistance.

Step 5. Inspection and Quality Control

Step 5. Inspection and Quality Control

After the tempering process, meticulous inspection guarantees quality and safety.

  • Trained personnel scrutinize the glass for surface flaws.
  • A polariscope ensures consistent internal stress patterns, important for strength.
  • Dimensions are verified to meet exact specifications.

Additional tests might be conducted depending on the application:

  • Impact resistance: How well the glass withstands blows.
  • Thermal shock resistance: How the glass handles sudden temperature changes.

Only glass passing all checks is deemed suitable. This step guarantees:

Following successful inspection, the glass is cleaned, packaged, and shipped, ready to be used.

Explore the Masterful Craftsmanship of Tempered Glass

Dive into our comprehensive guide and unravel the artistry that goes into creating this remarkable glass option.
*We serve Illinois and Milwaukee area.

How to Tell If Glass Is Tempered

Determining whether glass has been tempered can be challenging due to its subtle visual and physical differences compared to regular annealed glass.

However, here are some methods to help you identify tempered glass:

  • Look for a mark or label: Check for a manufacturer’s mark or label in one corner indicating that the glass is tempered.
  • Check for distortion: Tempered glass often has slight distortions, like waves or ripples, especially noticeable when viewing reflections or objects through the glass.
  • Inspect the edges: Tempered glass typically has smoother, rounded edges compared to regular glass, often resulting from grinding or polishing after tempering.
  • Look for stress patterns: Tempered glass may show faint stress patterns, known as “quench marks,” visible as small, parallel lines or spots on the surface.
  • Perform a polarized light test: Viewing through polarized sunglasses or a filter may reveal distinct patterns or colors in tempered glass due to internal stresses.
  • Conduct a tap test: While not always reliable, tapping the glass lightly with a metal object can produce a higher-pitched, ringing sound characteristic of tempered glass.

It’s important to note that none of these methods are foolproof, and the best way to determine if glass is tempered is to consult with a professional or the manufacturer. Additionally, attempting to test glass can be risky and may result in breakage or injury, so exercise caution when performing any of these methods.


The meticulous process behind tempered glass manufacturing yields a product renowned for its strength and safety. At Apex Tempered Glass, we specialize not only in tempered glass but also in tempered laminated glass, offering tailored solutions for diverse applications for customers across Illinois and Wisconsin. Contact us to explore how our expertise can elevate your projects with the reliability and durability of tempered glass solutions.

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!

Contact us today to schedule a consultation and bring your vision to life.