Spontaneously shattering auto glass isn’t something most vehicle owners really think about, but that doesn’t mean it doesn’t happen. While the phenomenon isn’t super common, it’s definitely possible, and since that’s the case, as a conscientious vehicle owner, you should know whether your ride is at risk and what to expect.

In this blog, we can explain what spontaneous auto glass explosions are, what usually causes them, and what you should do if this startling, unusual issue happens to you.

What Is Spontaneous Glass Shattering?

Spontaneous glass breakage is essentially what it sounds like: a sudden shattering, explosion, or less severe breakage in a sheet of glass that happens with no apparent cause. The phenomenon only occurs in tempered glass, a type of safety glass that comprises the rear window of most vehicles. Why tempered glass only?

Because tempered glass is created through a series of chemical or temperature treatments designed to make it more impact resistant than other types of glass. The “toughening” process required to create this type of glass places the outer surface of the glass sheet under considerable stress and compression.

The tensile stress in the body of the glass naturally balances the outer compression, which puts the whole sheet (or in this case, window) under considerable internal stress. Given the amount of stress the average safety glass rear window is under at all times; it can shatter suddenly if there’s even minor damage to the edges or interior of the glass. From the outside, however, the damage appears to occur for no reason whatsoever.

Risk Factors for Spontaneous Glass Breakage

Now that you know spontaneous glass shattering is a real thing, you’d probably like to avoid it if at all possible, right? How do you do that? Tend to back glass repairs or rear window glass replacement promptly if you notice even a minor indication of glass damage.

Aside from handling necessary auto glass repairs or window replacements as quickly as possible, you’ll also want to keep an eye out for these potential red flags:

  • Edge damage. Considerable stress can build around chips, cracks, or other imperfections in the edges of a tempered glass window. Over time, environmental stressors like temperature, wind, and road vibrations can put those glass imperfections under even more stress, which triggers spontaneous breakage.
  • Thermal stress. Extremely hot or cold temperatures can prompt glass contraction and expansion, and if the thermal stress exceeds the glass’s strength, the window will break. If you notice your vehicle windows become ridiculously hot in the sun or incredibly cold in winter, try to park in a covered area to minimize thermal glass stress.
  • Window frame changes. When the frame of a vehicle window incurs damage or changes shape for other reasons, the tempered glass inside it may no longer get adequate cushioning and protection. Driving vibrations, heat transfer from the vehicle frame, and excess frame pressure can all damage the edges of the glass and contribute to spontaneous breakage. 
  • Nickel-sulfide particles. When small pieces of nickel-sulfide get trapped within a sheet of tempered glass, they can compromise its strength and integrity. You probably won’t be able to detect nickel-sulfide in your vehicle window, and in reality, the risk factor for this issue isn’t high due to stringent glass manufacturing standards. It’s good to be aware of the potential risk nonetheless.

Post-Shattering Back Glass Replacement: How To Handle The Situation

If you’re ever the victim of a spontaneous window-shattering incident, try not to panic. Keep a cool head, pull over in a safe location, call the authorities for help, and begin documenting the incident immediately. Find your insurance information and start getting quotes from reputable auto glass replacement companies as soon as you can.

The type of auto coverage you have and the specifics of your policy will determine your next steps. If you can, try to work with an auto glass shop that will help you with your claim so you get the appropriate coverage for your situation. 

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