Learn about the differences between tempered and regular glass. Understand manufacturing, strength, durability, impact resistance, and thermal shock handling for informed decisions.
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The Manufacturing Process
The way glass is manufactured plays a critical role in determining its properties and applications.
Let’s take a closer look at how regular and tempered glass are made.
The Creation of Regular (Annealed) Glass
In the production of regular glass, the molten silica-based mix is cooled slowly under carefully controlled conditions.
This process, known as annealing, removes undesirable stresses from the glass.
Cooling happens in an annealing “lehr,” which is why we often refer to regular glass as “annealed” glass.
The Heat Treatment of Tempered Glass
Tempered glass undergoes a different process. After heating to a temperature near its softening point, it is forced to cool rapidly under carefully controlled conditions.
This heat treatment induces stress in the glass, resulting in increased strength, resistance to thermal stress, and improved impact resistance.
The fracture characteristics of heat-strengthened glass can vary widely, giving it unique properties depending on the level of compression applied during the heat treatment. Vitro Architectural Glass sums it up as:
Vitro Architectural Glass
- Heat strengthening and tempering are two processes used to heat treat glass for durability and safety. Heat strengthening makes glass 2x stronger while tempering makes it 4-5x stronger.
- Tempered glass has a minimum surface compression of 10,000 psi and breaks into small, cube-like pieces. Heat strengthened glass has 3,500-7,500 psi compression and breaks into large pieces.
- Tempered glass meets safety glazing standards due to its breakage pattern. Heat strengthened does not meet safety standards but its breakage helps glass stay in place.
- Distortion can occur in heat treated glass due to roller waves, bowing, and other factors. Doing mock-ups and using thicker glass can minimize distortion.
- The type of heat treatment depends on the application. Tempering should be used where safety glass is needed. Heat strengthening works for other applications.
Strength and Durability
Understanding the strength and durability of glass is crucial, especially when choosing the right type of glass for a particular application.
So, how does annealed glass stack up against tempered glass?
Regular, or annealed, glass is often used in situations where high strength isn’t needed.
While it’s a versatile and cost-effective choice for applications like window panes or table tops, its lack of heat and impact resistance limits its use in more demanding settings.
Additionally, when it breaks, it can form dangerous shards.
Tempered glass, on the other hand, stands out for its strength.
With a minimum surface compression of 69 MPa (10,000 psi) or an edge compression of not less than 67 MPa (9,700 psi), it can withstand much higher pressures and impacts compared to regular glass.
This makes it perfect for use in car windows, shower doors, and other areas where safety is paramount.
Impact Resistance and Safety Standards
Whether you’re designing a building or selecting a new coffee table, safety is often a top concern.
Here’s what you need to know about the impact resistance of regular and tempered glass.
Regular glass, despite being a common material in homes and buildings, has low impact resistance.
When hit with sufficient force, it can easily crack or shatter, producing sharp fragments that can lead to injuries.
Tempered glass has a considerably higher impact resistance, thanks to the heat treatment process it goes through during production.
If it does break, it shatters into small, pebble-like pieces that are far less likely to cause injury than the sharp shards produced by broken regular glass.
This makes tempered glass a safer option, especially in high-traffic areas or places where children or pets are present.
Thermal Shock and Breakage
Thermal shock refers to stress-induced within a material due to a rapid change in temperature. Let’s explore how regular and tempered glass respond to such conditions.
Regular glass, due to its basic composition and manufacturing process, is vulnerable to thermal shock.
A sudden temperature change can cause it to crack or even shatter, posing a potential safety hazard.
With its superior heat resistance (it can withstand temperatures up to 470 degrees Fahrenheit), tempered glass is much more resistant to thermal shock than regular glass.
Even if it does break due to extreme conditions, it shatters into small pieces without sharp edges, significantly reducing the risk of injury.
Installation, Cost, and Maintenance
While safety and performance are important factors in choosing between regular and tempered glass, practical considerations like ease of installation, cost, and maintenance should also be part of the equation.
The Ease of Cutting and Installing Regular Glass
Regular glass is easier to cut and install than tempered glass.
This is because once the glass has gone through the tempering process, it can no longer be cut or modified. Any attempts to do so would result in the glass shattering.
This makes regular glass a popular choice for DIY projects and installations that may need adjustment on-site.
The Challenges and Costs Associated with Tempered Glass
Tempered glass, although stronger and more durable, comes with its own set of challenges.
It must be cut and etched into the final desired shape before tempering, which can make the manufacturing process more complex and costly.
However, its high durability and safety features often justify the extra cost, especially in commercial and industrial applications where high strength and safety are paramount.
FAQs about Types of Glass
We understand that choosing the right type of glass can be confusing, especially when you’re dealing with complex terms and technical details.
Here, we answer some frequently asked questions to help clarify things.
How can you tell the difference between tempered glass and regular glass?
It’s not always easy to tell the difference just by looking at them. However, one way to spot tempered glass is by examining it under polarized light.
Tempered glass will show patterns from the cooling process, while regular glass will not.
Also, tempered glass has smooth and rounded edges due to the additional processing, whereas regular glass does not.
How strong is tempered glass compared to regular glass?
Tempered glass is up to five times stronger than regular glass.
It’s manufactured under a process that increases its tensile strength, enabling it to withstand higher pressures and impacts.
This is why it’s used in situations where safety and durability are crucial, such as in car windows and shower doors.
How many times stronger is tempered glass than regular glass?
Tempered glass is generally four to five times stronger than regular annealed glass. It undergoes a heat treatment process that puts the outer surfaces into compression and the interior into tension.