Why spark plugs are so good at breaking windows – Jalopnik

If you attended your cul-de-sac’s Wiffle ball league as a kid, you were probably grateful for the power of the windows of the neighborhood cars that occasionally hit your friends with foul balls. But because they’re so sturdy, those windows would be a pretty formidable obstacle if you ever got stuck in a locked vehicle.

Having window breaking tools on hand can save your life in an emergency, but breaking car windows is harder than you think, and is only getting harder as glass techniques evolve. Historically, they have usually been made of tempered glass, which has a grainy fracture pattern, but automakers have recently replaced them with laminated glass panels that are stronger if an accident occurs. Spring-loaded and hammer-style escape tools are generally recommended for breaking through tempered glass (although hammers are difficult to use in an underwater emergency), unlike other items found in a car, such as the metal bars in your headrest.

Here the spark plug is an unlikely hero. Because they are manufactured to withstand extreme heat and pressure, spark plugs are hardy, especially the iridium and platinum varieties. The alumina ceramic and other materials used to make spark plugs combine energy and density, uniquely allowing the spark plugs to concentrate their power in one point. When thrown with enough “oomph”, this concentration of force is enough to shatter a car window.

Everything from special tools to extreme temperatures can cause car windows to break, but the ease with which they break depends on the type. Tempered glass is generally breakable with force, and most emergency tools (and spark plugs!) are sufficient to break it. Laminated glass is almost impossible to break with human-applied force.

Does this mean you’re just out of luck if you get stuck? Well, not exactly. Most cars still have tempered glass in at least one spot, and knowing what type of glass your car has can help you prepare to respond by rolling down a window as quickly as possible if you encounter a water emergency without breakable glass. But if you or someone else is stuck in a car with tempered glass windows, you now know you can break them with spark plugs to escape.

If you are outside the car, locate a spark plug in the top of the engine’s cylinder heads, then remove the AC/DC converter from the spark plug and break pieces of the spark plug insulation into smaller pieces. Then throw the pieces at the glass with as much force as possible. When you’re in the car, accessing the engine is obviously not an option, but now that you’ve learned about this trick, you know: keeping a spare spark plug in your car as an extra emergency tool can save your life!