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  • You can shatter a car window by hitting it with a sharp, broken shard of white ceramic from a spark plug’s insulator.
  • The spark plug’s insulator is usually made of aluminum oxide ceramic, which has a higher hardness rating than annealed or tempered glass.
  • Remember that keeping spark plug shards might be illegal in your state and windshields and bulletproof glass are tougher to break than windows.

Car windows are durable to keep you safe on the road. That’s both good and bad. The stronger the glass that comprises the window pane, the less likely it will break if something strikes it forcefully. However, that same sturdy glass pane can also prevent a hasty escape from your car during a severe accident. If you need to escape your vehicle in an emergency, you’ll need something that can break windows easily.

You might have heard that spark plugs make an excellent emergency breakout tool. But can a broken piece of a spark plug break a window glass?

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mechanic showing a spark plug
Most spark plug insulators use aluminum oxide ceramic, which has a higher hardness than the annealed or tempered glass that makes up most car windows.

Can a Spark Plug Break a Window?

You can shatter a car window by hitting it with a spark plug. Specifically, use a shard of white ceramic that serves as the plug’s insulator.

Break the ceramic insulation material into smaller pieces. Pick a shard with a sharp point, taking care to avoid injuring yourself.

Throw the broken shard of the spark plug like a dart so that the pointy end strikes the glass. Aim for either the window’s center or one of its corners. If you go for a corner, target the one near the top of the door.

Keep your distance from the glass to avoid shattered glass or ricocheting ceramic. If other people are standing nearby, warn them to move back.

Why Does a Spark Plug Break a Window?

Most spark plug insulators use aluminum oxide ceramic. This porcelain has higher hardness than the annealed or tempered glass that makes up most car windows.

Furthermore, spark plugs tend to break into pieces with sharp edges and points. If an edge or point hits something, it can apply a lot of force to a tiny surface area of the glass.

hand holding a new spark plug
REMEMBER: Spark plug shards are illegal in some states because they are regarded as weapons in those states.

Things to Remember About Breaking Windows With Spark Plugs

Before you find the nearest spark plug as an emergency car glass breaker, it pays to keep the following in mind:

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Keeping Spark Plug Shards Might Be Illegal in Your State

Some states regard spark plug shards as a weapon. Why is that? Because you’re not the first to think about using a broken piece of a spark plug to shatter a window, and other people might have less than lawful motives.

Burglars and car thieves have used the same technique to break into cars. Depending on your home state’s laws, you can get fined or imprisoned for carrying a spark plug chip. Always check state legislation to see if this practice is forbidden.

Windshields and Bulletproof Glass Are Tougher

Throwing a spark plug shard might not immediately work on a windshield or bulletproof glass. Ordinary car glass is either annealed or tempered glass. Both materials easily give way to the ceramic of the spark plug insulator.

In contrast, many windshields have a laminate layer that can withstand greater impact. Meanwhile, most bulletproof glass uses sturdier materials, such as acrylic or polycarbonate. You can still break through them in time, but it will take much more effort.

It’s best to call for professional assistance when you need to get in or out of your car. However, a spark plug can get you out of trouble by letting you break a window in an emergency.

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Where to Get Quality Spark Plugs for Your Vehicle

If you’re in a pinch, storing some spare spark plugs in your vehicle might just save your life. Of course, these spares are also useful if your engine’s current spark plugs happen to break down. Whatever the case, if you want to have spare spark plugs on hand in case of an emergency, has you covered. has a great catalog full of quality aftermarket parts at every price point to suit your budget. We aim to offer the best deals, which is why our price match guarantee is in place to help you save on the parts you need. Enjoy fast shipping and receive your life-saving spark plugs in as few as two business days if you order now. If you have any questions or concerns, feel free to reach out to our friendly and helpful customer support team.

Place your order for new spark plugs on today.

About The Authors
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Automotive Features Reviewer at

Lisa Conant grew up in Canada around a solid contingency of gear heads and DIY motor enthusiasts. She is an eclectic writer with a varied repertoire in the automotive industry, including research pieces with a focus on daily drivers and recreational vehicles. Lisa has written for Car Bibles and The Drive.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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