What causes a windshield to fog up on the inside? I understand it’s related to the differences in temperature, but that’s as far as I understand. What can one do to resolve it?
Sorry if the flair is wrong 🙂
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When it’s cold outside the car and warm inside the car, the windscreen itself gets cold.
This means that moisture in the air inside the car – usually from the breath of people sat inside – condenses into liquid water when it hits the cold windscreen. Which then sticks to the windscreen, creating that fog. It’s the same principle as a cold drink getting wet condensation on the outside.
You can fix it two ways – either by equalising the temperature between inside and out, or by removing the moisture.
Most of the time, you don’t want the inside of the car to be as cold as the outside. 🙂
Older cars have vents which blow air at the windscreen, which both warms up the glass a bit and helps dry the area out. Other cars have things like heated windscreens, which keeps the windscreen too warm for water to condense onto it.
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