Frost Formation on Windshields

When the weather turns cold, some of us begin the morning with scraping frost off the car windshields. This frost forms when evaporating water turns into a solid, thus glazing a car windshield with ice.

Dew Point

• Argonne National Laboratory scientist Larry Krengel reminds us that frost forms when the air's dew point and temperature near, reach or drop below freezing. Dew point measures the amount of water vapor in the air: the more water, the higher the dew point.

Temperature

• Heat radiating from surfaces significantly affects the formation of frost. The Department of Atmospheric Sciences at the University of Washington states that, "as the sun sets on cold, clear nights, the surface temperature plummets (as the earth radiates heat into space), and the air near the surface can cool to the dew point temperature." When the inside of the car is -- or has been -- warm, and the air outside the car isn't, the heat radiating outward forces the water in the air inside to the windshield's surface, where it freezes.

Prevention/Solution

• Using a garage, covering the windshield or applying nighttime de-icer sprays prevent frost formation. To remove frost, turn on the car and its defroster setting, or pour a cup of lukewarm water over the windows to gradually warm the glass and melt and loosen the frost. If all else fails, there's always the good ol' ice scraper.