Why Do Spark Plugs Break Windows?

By John Adebimitan

You may have seen posts about how easy it is to break windows with spark plugs, and you are probably wondering if it is true. Well, yes, it is.

It may sound weird, but breaking windows with spark plugs is effective. Read this article to find out why spark plugs can easily break windows.

Why Do Spark Plugs Break Windows?

To answer this question, let’s first talk about window glasses.

Most window glasses – aside from car windshields – are usually made with tempered glass. Though tempered glasses are generally very strong, they have a common weakness resulting from their manufacturing process.

During the manufacturing process of tempered glasses, they are usually rapidly cooled from liquid to solid. When this happens, the outside of the glass cools rapidly; meanwhile, the inside doesn’t.

This results in a glass with a lower density and a higher volume compared to glasses that cool slowly. Consequently, the outside portion of tempered glasses usually has high surface compressive stress, while the inside has high internal tensile stress.

The takeaway from this is that the entire manufacturing process of the tempered glass is already acting as a crack inhibition method. This means that once you can overcome the compressive stress on the outside, the glasses’ internal stress will do the rest of the breaking.

In other words, you simply need to force a crack that penetrates the thin compressive stress layer outside the glass. When you do that, the tensile stress that the glass stores internally will break the glass completely.

This is where the spark plug comes in. Since spark plugs are made from aluminum oxide ceramic which is very hard, they are strong enough to make an impact that will form a crack.

Immediately they make the crack, the internal tension in the glass will spread through the entire surface, causing it to shatter. 

How to Break A Car Window with A Spark Plug

Below is a step-by-step procedure you can follow to break a car window with a spark plug

  • STEP 1: Since the ceramic portion of the spark plug breaks the window, you need to break off the metal connection end of the plug.

If you find that hard to do, try to sharpen the ceramic part by hammering on it enough to break off tiny pieces so you can get sharp edges.

  • STEP 2: Scribble an X pattern on the window to make it easy for you to target the center of the glass. Targeting the center will make it easier for you to pop the glass.

An alternative you could try is to target the edges of the glass.

  • STEP 3: Once you’ve picked your preferred target, keep a reasonable distance between yourself and the car window. Then throw the plug at your targeted part on the window.

With enough force, the spark plug will create enough damage to shatter the window.

How Do You Break A Car Window Quickly? – The Different Options You Have

This section discusses some options you can try when you want to break a car window quickly.

1.    Using a spark plug

A spark plug is one of the fastest ways to break a car window. Note that the ceramic part of the plug is what you need the most.

You can get rid of the metal end of the spark plug to leave the ceramic part exposed, or you smash the ceramic part into pieces. If you can get rid of the metal end, you should now have an exposed sharp ceramic end.

Target the center or an edge of the window. Now throw the spark plug or the ceramic pieces you’ve broken off at your target center on the window.

If you’ve applied enough force, stand back and watch the glass shatter.

2.    Use Porcelain bit or Ninja Rocks:

When you need to break your car window quickly, something small and sharp like a porcelain bit or ninja rock can help you do the job.

Stand away from the window and throw the porcelain bit or ninja rock at the edge of the glass. If you’ve added enough pressure, the glass will shatter upon the impact of the porcelain bit or ninja rock.

3.    Use an emergency hammer:

You can also use an emergency hammer to break a car window quickly.

In the case of an emergency, you can use the metallic end of the hammer to hit on the edge of your car window. Once you can crack the window, it will begin to shatter.

4.    Use a standard EMT device:

This is the most time-consuming of all the methods we’ve considered so far. In this method, you will need to use a standard EMT device.

The standard EMT device is a tool the police and emergency units use.

Before you use this tool, you will need to cover the glass with duct tape to hold the pieces together because it will make the usual noise of breaking glass. After doing that, hit the center of the glass to break your car window.

5.    Make use of an automated steel punch tool:

Though carpenters and plumbers mostly use this item as an electronic center punch steel tool, you can also use it to break your car window.

Simply press it against the glass and then release the spring so it can release a punch effect on the glass. Doing that will create a hole in the glass.

The glass will shatter from the effect the hole makes.

Read also:  Best Lumbar Support for Car Seats

How to Break Spark Plug Porcelain

The easiest way to break off the spark plug porcelain would be to use a hammer or blade made for ceramic tiles. Such a hammer or blade would be built with carbide or diamond.

If you can’t get one, you can use a regular hammer. However, you will need to hit the hammer down on it very hard to break the ceramic part of the spark plug.


Now you can conclude that it is true that spark plugs can break windows.

Since they have a ceramic component that is more rigid than glass, spark plugs can break your windows with ease.

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