The classic image of glass is something that shatters under the least amount of stress. As they say, people who live in glass houses shouldn’t throw stones. But not if the house was made out of a safer type of glass.
We actually encounter these safer glass surfaces everywhere: from windscreens to balustrades to windows to coffee tables to the floors of raised walkways. Even though it’s unnerving to step onto a glass surface high above the ground, you can do so these days. Glass can be very tough.
There are two general types of stronger glass: Laminated Glass and Toughened Glass (also called Tempered Glass). They are both very useful, but they also differ in big ways.
How Laminated and Toughened Glass are made
Laminated glass is created by bonding several sheets of regular glass with sheets of plastic in between them. The effect is that, if the glass breaks, it still stays together, creating a web-like effect. You can make a hole in the glass surface, but otherwise it stays intact. One common example is a windscreen:
If you think of what happens in a car accident. The windscreen cracks, but the glass does not shatter into the car. There are two normal annealed panes of glass — there could be multiple — with a Polyvinyl Butyral or EVA laminate in between. When it does take an impact, the glass breaks, but it sticks to the laminate virtually in one piece. So there aren’t large shards of glass that come off. But don’t forget this is still normal glass. Once that laminating comes off, and it can over time, the glass can be as dangerous as a regular pane.”
Toughened glass is quite different. This is glass that was baked at very high temperatures, making it incredibly strong — hardy enough that it cannot be shaped or cut afterwards. Toughened glass is more flexible, and can shatter, but creates many small pieces that are unlikely to cause serious cuts. The other windows on a car are typically toughened glass.
That’s very important to remember. Neither should cut you, but one remains ‘intact’ and the other does not
The differences between Laminated and Toughened Glass
Other than how they are made, the important differences between these two glasses are in their uses. Toughened glass can be installed without a frame, but laminated glass requires a frame to protect it from de-lamination.
As soon as laminated glass comes into contact with water, it can start to delaminate. So you use a frame to keep the edges protected. But toughened works for framed and frameless applications, such as glass balustrades or stacking doors.
Laminated glass won’t shatter and is arguably a bit stronger due to the extra layers. But it is still normal (annealed) glass. Toughened glass can be incredibly strong.
Which to use depends on several factors, including safety regulations. If you want to ensure someone can’t fall through a pane of glass, such as a large window or shower, laminated glass is often the choice. Toughened glass may be stronger, but once it breaks it leaves a hole, creating an ongoing hazard.
But if glass is freestanding, in other words not supported completely by a frame, it often has to be toughened. Toughened glass is distinctive enough to have its own standards: by law each toughened panel must have a stamp on it, identifying the company and other information such as numbered codes. The same is true for laminated glass.
The acoustic properties of Laminated and Toughened Glass
If the glass is tougher or incorporates layers of plastic, is it better for managing sound as well? Can safety glass also block noise? The place to start is the frame:
Acoustics depends a lot on what happens around the glass. So if you have an acoustic frame that seals things, that will have a big impact on acoustics overall. You can use acoustic glass, but if it’s surrounded by a regular aluminum frame, it won’t do much. Acoustic management is a system involving the glass and what’s around it.
Glass is very complimentary to sound. It resonates and vibrates at normal frequencies, making it easy for sound to travel through. This property does not change significantly if a glass has been toughened or laminated, though there can be a difference especially if more layers are added. There are also other methods. You can laminate two different thicknesses of glass together, or create an air gap. This will change the frequencies, which interfere with the sound waves.
Acoustic glass is usually treated with acoustic vinyl, which like a laminate is applied to the glass. So it is entirely possible to have safety glass that also manages sound.