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How to De-Fog a Windshield

Last updated 6 years ago


Fog on a windshield is not only a nuisance—it’s also a hazard, as the amount of moisture on the windshield can obscure your view of the road. There are a few ways to get rid of the windshield fog that inevitably accompanies driving in cool and moist climates, but understanding what causes your windshield to blur with condensation is important before you can decide which method is best.

Physics Principles at Work

What happens on your windshield when it becomes obscured by fog is known as a change-of-state. A variety of factors like temperature and pressure dictate whether a substance will take the form of a liquid, gas, or solid. When water vapor in the air hits a cold windshield, it undergoes a change from a gas to a liquid, condensing on the glass and obscuring the view.

Finding Equilibrium

One of the quickest ways to get your windshield to go from foggy and opaque to crystal-clear is by opening the windows of your vehicle. Since the water vapor inside of the car is warm and condensing on the windshield, lowering the inside temperature of the windshield and water vapor around it will help prevent condensation. This is especially effective when the weather is cold and dry, and is one of the fastest ways to de-fog your windshield.

Using your Defogger

If opening your windows just isn’t feasible, then utilize your defogger. The defogging setting of the car will push air onto the windshield, evaporating condensation with heat and air circulation. If this doesn’t work, then try matching the temperature of the blowing air to the outside temperature for immediate results.

If you need affordable and experienced auto glass repair services in the Northern California area, then call Glass on the Move at (510) 338-4791.


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