Why Do Spark Plugs Work so Well at Breaking Windows?

Did you know that spark plugs can easily break tempered glass in vehicles and shatter tempered glass to pieces? As unusual and unlikely as it may sound, this is quite easily achieved, as many YouTube videos demonstrate. Take a look:

But even after seeing these “spark plugs breaking car window” videos, the purpose of the demonstration may still remain unclear. After all, what are the chances that spark plugs will hit the tempered glass of your window in real life?

In this article, I will answer this question and look at how this nifty multitasking tool can save your life.

What is a Spark Plug?

There is no doubt that most car owners already know what spark plugs are and how they work. But for those who are hearing about it for the first time, it isn’t too difficult to understand, and below I will provide you with all the information you need to know the technical and nifty method of using a spark plug. Despite the differences in configurations and the technologies they use, all gasoline engines have spark plugs. Their job is to ignite the air-fuel mixture inside your vehicle’s cylinder at a precise moment. The resulting explosion will generate the power that moves the car forward.

Why Do Spark Plugs Break Windows?

Although spark plugs don’t weigh much, it still breaks tempered glass easily with little force. But this is not what makes it different from any other object that would cause the same thing. So you see, spark plugs can break safety glass, side windows, and a rear window of vehicles.

They can break windows because of their material composition – exceptionally hard aluminum oxide ceramic, otherwise known as porcelain. Spark plugs focus energy in a small area when thrown with reasonable force. Because of the spark plugs’ material and size, it results in tempered glass shattering. When used for breaking car windows, spark plugs are known as “ninja rocks,” and this is because of how easy it is to break windows.

How to Break a Window Using a Spark Plug?

As simple as it sounds, you will need only two things to break a window of a vehicle:

  • A spark plug (which can be new or used).
  • A ball-peen hammer.

Still, to prevent any potential injuries, protective equipment such as eye goggles and gloves would be a good idea. This exercise could result in tiny shards in your eyes or glass flying everywhere. Spark plug fragments could also end up cutting you.

Now that you have everything prepared, these are the steps you should follow:

Step 1: Grab the spark plug at its metal end with one hand and press it firmly against the floor or workbench.

Step 2: Swing the hammer with the other hand and moderately hit the white spark plug insulator. You may need to repeat this several times until the ceramic falls apart.

Step 3: Carefully pick big pieces, which you will use in the next step.

Step 4: Take your position in front of the side window smashing it at a distance of several feet. Then, aiming at one of its corners, throw a spark plug segment towards the window. Again, try to be moderate, as this will not need moderate speed.

Note: If the window stays intact, and there is no sign of a breaking point, you should repeat this step and throw your improvised projectile a bit harder – as you could have used too little force. When the window finally breaks, it will probably shatter into pieces on its own. Clear the debris before you cause injury to yourself.

Why Would You Want to Break a Car Glass with a Spark Plug?

Having established why spark plugs break tempered glass and how to do that, we come to the obvious question. Why would you want to break your vehicle’s tempered glass with spark plugs? A spark plug is a vehicle component that lives deep inside the engine bay, and it’s not likely to fly out of there on its own. This eliminates the possibility of running into them on the road.

Believe it or not, knowing how to use a spark plug to break windows may save your life!

Though a hard object such as a rock or piece of metal might also be able to do the job, the chances of you having that in your possession inside your vehicle are very slim! However, a spark plug is a small object that is easy to store and find at a hardware store. 

You should always ensure that you keep a spark plug in your glove box. If you are in a situation where you are trapped inside your car, your multitasking spark plug could save your life. Glass breakage will work if you are trapped inside a vehicle above or underwater, as not much force is needed to break the window when using a spark plug.

You will be able to break a car window and escape without enduring any cuts, as the tempered glass will break into cubes and should not leave any sharp edges of the glass.

Please note that you should be careful when handling the spark plug, ensuring it doesn’t break when you are placing it in your vehicle as spark plug porcelain shards could cause harm.


As we have explained in this article, spark plugs can end up breaking car glass. But, it’s only used to break the glass. A spark plug insulator is a part of an engine component used to make a vehicle drive. However, it can be used as a nifty gadget when you find yourself in a less-than-ideal situation.