Why do spark plugs break a car’s window?

Car windows are often made from highly hard materials to break easily; their surface is made with comprehensive stress and high tensile stress granting them durability and strength and making them shatter into many tiny pieces when broken.

This, therefore, means that it is not easy to break the car windows as easily as you can think. This is so because while manufacturing, the glass is quickly cooled from liquid to solid.

When cooled this quickly, it means that it ends in lower density and higher volume than one that is slowly cooled. There is a thermal gradient in the glass pane as the glass cools since the outside cools faster, and the inner part does not.

Therefore, compression on the outside glass while tension is put on the inside. This method will act as a crack inhibition since the stress necessary to propagate the crack should first overcome the outside glass’ comprehensive pressure.

So the result is that the glass is too strong to be broken. But I believe you might have seen various posts about how to break this glass with a spark plug like those in windows or windshields.

It is actually simple to break a window with a spark plug, but how and why do spark plugs break any glass so easily? What is contained in the sparkplugs that makes this possible. Check out.

Why do spark plugs break a glass window?

Car windows are strong enough to withstand damage, but spark plugs can break through them so easily. This is because spark plugs are made of aluminum oxide ceramic or porcelain and can put a significant amount of energy on a single point on this glass.

The ceramic contained in these plugs break glasses so easily. Ceramic is known to be a more complex object than glass; therefore, even with minimal force, it can ruin a glass.

Most car windows are made of tempered glass that is best known for strength but can also break catastrophically. Glass windows are robust, and due to the heating cycle, it contains a significant amount of internal energy.

This energy makes the glass highly sensitive even to more minor damages from the spark plug. The ceramic found in spark plugs concentrates energy on a precise area, making it easy to break.

Generally, the ceramic component contained in a spark plug produces enough damage that it can shatter a glass.

How is a spark plug so efficient in breaking windows so fast?

A spark plug can efficiently break windows so fast because of the shape ceramic component contained in this device. After getting a chip with a sharp edge, you need to throw it at the glass window while at a distance.

According to physics and science, the ceramic material is heavier than the window’s glass on the hardness scale. However, it would be best if you were careful while handling porcelain chips to prevent injuries to your hands.

Because of the compressed energy on the glass inside, a force that can break the entire surface of glass concentrates on a single point.

This is where a tempered glass weak point lies with just a small spot of the glass coming to contact with the spark plug’s ceramic, creating a pressure point and making the glass shatter to pieces.

Therefore, a spark plug is efficient in breaking glass because the hard aluminum oxide ceramic found in the spark plugs puts the impact energy in the grass’s precise area.

Does a spark plug break all types of windows?

Spark plugs can break windows made of tempered glasses. However, these devices cannot break all windows. Because of the aluminum oxide ceramic contained in the spark plugs, the spark plugs can easily break tempered glass, float glass, tinted glass, and bulletproof glass.

Although there are some exceptions, a spark plug can impact even a resistant glass. However, it depends on the precision and hitting force used in hitting the glass.


Spark plugs can break glass easily because of the ceramic components it contains. These ceramic components are responsible for breaking glasses as they are more rigid than glass. Due to this rigidity, the spark plug can destroy a car’s windshield even with less effort.

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