The Uses and Benefits of Tempered Glass

Unless you are involved in a field of work where glass manufacture or use is front and center, it’s a good bet that you haven’t given much thought to tempered glass and what makes it different from annealed (i.e. ordinary) glass. 

Tempered glass has an incredibly important role that really can mean the difference between life and death. Not only do we find it in the windows in vehicles, but also glass shower enclosures, skylights and even parts of bulletproof glass. It’s in virtually every part of our lives, but most of us don’t know much about tempered glass. 

More than likely, you’ve either used or been protected by an item containing tempered glass, although you might have heard it being called “safety glass.” Both tempered and laminated glass are considered safety glass. 

What is Tempered Glass?

Tempered glass is glass that has been subjected to thermal and chemical treatments designed to make it stronger.

Francois Barthelemy Alfred Royer de la Bastie, born in 1830 in Paris, is thought to be the first person to develop a consistent method of tempering glass, even though the effect has been known for centuries. 

Bastie’s method involved quenching nearly-molten glass in a bath of hot oil and grease. In 1877, Germany’s Friedrich Siemens invented a different method that involved pressing glass in cool molds. This process produced a type of tempered glass that was stronger than Bastie’s. 

Working from these first two efforts, in the 1920s Austrian chemist Rudolph A. Seiden created and patented the first complete process for making tempered glass.

What is Annealed Glass?

Annealed glass (aka ordinary or standard glass) is made when molten glass has been allowed to cool slowly once it has been shaped. One of the cheapest forms to manufacture, annealed glass is easy to work with since it can be cut without breaking. 

Since this type of glass is far weaker than tempered glass and tends to form jagged shards when broken, nowadays its mainly used in applications for which safety and strength are not a priority, such as in cabinet doors and household display cases.

How is Tempered Glass Made?

Tempered glass is annealed glass that has been subjected to thermal or chemical treatments to become four times stronger. The process is as follows:

  • After being placed on a roller table, a sheet of glass is moved through a furnace and heated to around 620°C. 
  • The surface of the glass sheet is then rapidly cooled with forced air, while the inside remains molten for a time. 
  • This cooling puts the inside of the tempered glass in a state of compression, which generates a stress pattern within the glass and results in its increased strength. 
  • When tempered glass is broken, all the energy stored in that stress pattern is released at once, shattering the glass into thousands of dull granular chunks, rather than sharp shards.

Annealed glass can also be toughened through a chemical treatment that forces the surface of the glass into compression through ion exchange. The sodium ions on the surface of the glass are exchanged for potassium ions by submerging the glass sheet into a chemical bath of potassium nitrate. 

This method of toughening results in tempered glass that is stronger compared to making toughened glass with a thermal treatment. Chemical treatment is often applied to objects with a more complex shape. 

Where is Tempered Glass Used?

Tempered glass is used where safety and material strength are necessary. 

This includes:

  • Passenger vehicle windows (except the front and rear windscreens, which are made of laminated glass)
  • Cookware and dining ware
  • Diving masks
  • Shower enclosures
  • Glass doors
  • Glass tables
  • Aquariums
  • Refrigerator shelves
  • Cell phone screen protectors
  • Sports and gym facilities
  • Greenhouses
  • Tempered glass windows
  • Bulletproof glass components
  • Glass walls
  • Retail and museum display cases
  • Patio doors

The Benefits of Tempered Glass

Using tempered glass has many benefits, such as:

  • Safe breakage. When broken, tempered glass shatters into small, harmless chunks, instead of jagged shards.
  • Strength. Tempered glass is known to be four times stronger than annealed glass.
  • Up to code. Building codes in many countries require tempered glass to be used in skylights, windows, doorways, sliding doors, elevators, fire department access panels and many other applications.
  • Framed. When tempered glass is also laminated, it will not fall out of its frame when broken.
  • Flexibility. Although tempered glass is very flexible in terms of what it can be used for, it should be noted that it does have the limitation that it can’t be cut once it’s gone through the tempering process. 
  • Aesthetics. Tempered glass can be finished with a beveled edge or just a polish to add further beauty.
  • Heat resistance. Due to the thermal treatment that tempered glass is subjected to in the manufacturing process, it has greater heat resistance than annealed glass.
  • Scratch resistance. Tempered glass is often used as a screen protector for cell phones because it is resistant to scratching.
  • UV protection. Tempered glass has an SPF factor of about 16 because it absorbs up to 65% of UV rays that pass through it.
  • Fire safety. Since tempered glass is resistant to heat, it stops radiant heat from flowing into the house from the outside. This is especially helpful in the event of a wildfire, or a fire in an adjacent building.
  • Security. Tempered glass is more impact-resistant than typical annealed glass, so break-ins can be stopped before they get any further than the window.

Tempered Glass and You

In addition to the added safety, security and strength of tempered glass, many people find it appealing to look at it. 

Aside from being naturally attractive, decorative touches can be added to tempered glass that improve the visual appeal and increase the possibilities for its use. 

For extra peace of mind about the safety and security of your family home or business, consider adding tempered glass windows and doors.

Budget Glass, based in Nanaimo, BC provides residential, auto and commercial glass products across central Vancouver Island. Our team are experts in working with tempered glass in multiple applications. 

Want to introduce more tempered glass within your home or commercial property? Contact us today and ask us how we can help.