Heard of Auto Glass Shattering Into A Million Tiny Pieces?

On occasion, you may have heard of auto glass shattering into a million tiny pieces suddenly and unexpectedly. The person swears nothing hit the window, but still it shattered. What could have caused that?

To learn the answer, we need to know what auto glass is made of and understand its properties.

The Shattering Auto Glass Mystery

What Is Your Auto Glass Made Of?

There are two main types of auto glass: laminated and tempered.

Laminated glass is the only type of glass used for your windshield. Some manufacturers also use it for the side or back windows, though most of the time the sides and backs are made of tempered auto glass.

Laminated Auto Glass

There are 3 main reasons laminated auto glass needs to be used for the windshield:

1. It is better able to resist projectiles from outside the vehicle (rocks, etc.)
2. It is better able to keep objects inside the car (people in the event of a rollover, airbags which deflect off the windshield before catching the passenger.)
3. It is better able to support the roof and integrity of the vehicle structure in the event of a crash or rollover.

Laminated glass is made of a thin layer of polyvinyl butyral (PVB) inserted between two layers of solid glass. The glass and PVB are sealed with pressure rollers and then heated, mechanically and chemically bonding them all together. The PVB allows the auto glass to absorb energy during an impact, and gives it strength to resist penetration by flying objects. It also deflects up to 95% of ultraviolet (UV) rays from the sun.

While laminated glass can break and be punctured, it will stay mostly intact because of the PVB.

Tempered Auto Glass

While laminated auto glass is used for the side and back windows on occasion, for the most part your vehicle probably has tempered glass installed.

While tempered glass is not quite as strong as laminated glass, it is still stronger than the glass windows of your home. Tempered glass is put through a heating and rapid cooling process which strengthens its outer surface (which cools faster and contracts) and core (which cools slower and expands.) These stresses give tempered glass 5-10 times the strength of ordinary glass.

When tempered glass breaks, it shatters into tons of tiny dull pieces due to the stress it is under.

Auto Glass Can Shatter Unexpectedly (Rarely)

You may have heard stories of people driving down the road, or simply standing near their vehicle, when the back or side window shatters into a million tiny pieces suddenly.

This can happen, though it is rare, and it only happens with tempered glass, so luckily the pieces are small and dull.

The reason this happens is not because the person didn’t see an object hit the glass, but likely that the glass has taken a hit or two before, and the stress from those hits, chips, or cracks along with additional stresses, possibly from potholes or the heat of the sun, can cause the auto glass to shatter at an unexpected time.

One way to prevent a huge mess to clean up in a shattered glass situation is to have tint applied to your side and back tempered auto glass. The tint is a thin layer applied to both sides of the glass, which will hold the glass together in the event it shatters, preventing a million tiny pieces of glass from spreading all over your car.