Hot water on cold windshield

If you live in a cold climate, then you’re probably familiar with the dreaded task of clearing your car’s windshield of ice and snow. Some people opt for a standard scraper or an ice-melting chemical spray. But one simple solution that works wonders is hot water. It melts the ice quickly and easily, making it an excellent alternative to scraping or waiting around while your car defrosts naturally (which can take hours). But does this mean that you should throw boiling water on your windshield? Well… not exactly…

What are car windshields made of?

Your car windshield is made of laminated glass, which means it has a layer of plastic between two layers of glass. The plastic layer makes the windshield more flexible and prevents cracks from spreading. This composite is much stronger than either type of glass alone, but if you apply enough force to your windshield with your wipers or by kicking your car door, it can break just as easily as any other piece of glass would.

Will hot water crack a cold windshield?

In short, hot water won’t crack your windshield. But it can damage it if you’re not careful.

While we’re on the topic of crack-free windshields, let’s address another common question: Is it safe to use hot water to clear ice from a windshield? The answer is yes—but only if the temperature of both your car and your water is low enough. If you pour boiling water from a tea kettle onto a cold windshield and allow it to sit for too long, you’ll end up with numerous cracks in your glass. So be sure to take these precautions before using hot water as an ice removal tool:

  • Make sure both the car and the water are at room temperature (around 75° F). Your vehicle should also have been parked in a garage or under cover for several hours beforehand so that its windows don’t freeze over when exposed directly to harsh sunlight.
  • If possible, remove ice with basic scraping tools before applying heat.* If removing snow or frost with anything other than warm liquid would damage any part of your vehicle’s bodywork (such as painted surfaces), then skip this step altogether!

Why does hot water crack a cold windshield?

You’ve probably heard that hot water can crack a cold windshield, but what does that mean? Hotter water is more viscous than colder water.

This means that it takes longer for hotter liquids to change shape and flow into new spaces. This is why you should never pour hot coffee on your lap—the heat from the liquid will cause burns along with its slow movement.

When you pour warm or hot water on a cold car windshield, it expands and shifts inside the glass without spreading evenly across its surface. This causes stress lines to form at points of high tension along which cracks can form when temperatures drop again during winter months.

What is the easiest solution to thaw a frozen windshield?

You can remove ice with a scraper, but it’s much more effective if you first use the defroster. If you have an older model of car, your car probably doesn’t have a built-in defroster. In that case, you’ll need to purchase one or get assistance from someone who has experience using one.

The most effective way to defrost your windshield is by using hot water on it—you might even be able to do this at home by filling up a sink or other container with hot water and placing the container on top of your dashboard (don’t put any part of your body near the heat source). You can also use any other heat source as long as it isn’t too close to plastic parts of your vehicle—this includes using heating pads and blankets, space heaters and hairdryers (watch out for any exposed wires), etcetera.


We hope you’ve learned a little more about how hot water can affect your car’s windshield. If you want to avoid the risk of cracking your windshield, our best advice is to leave it alone. However, if you think the ice is too much for you and need help getting through until it melts naturally, we recommend using a de-icing chemical like Klean-Strip Ice Melter or WD-40. Just be sure not to spray any chemicals directly onto the glass—instead spray them on some newspaper or towel first before applying them to your car’s surface.

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