Have you ever opened your car door on a cold or humid morning only to be greeted by fogged-up windows, a musty smell, or damp seats? Many drivers assume this is just part of winter or rainy seasons. But there’s a shockingly simple, low-cost solution that has been quietly used for decades: putting a glass of salt inside your car.
This viral tip isn’t folklore or superstition. It’s rooted in basic chemistry and real-world physics. In this article, we’ll break down why it works, how to do it safely, and when it’s especially effective—plus a few smart variations every driver should know.
Why Moisture Inside Your Car Is a Bigger Problem Than You Think
Before understanding why salt works, it’s important to know why excess moisture inside your car is harmful.
Common causes of moisture buildup in cars
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Wet shoes, umbrellas, or clothes
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Rain or snow carried in on floor mats
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Temperature differences between inside and outside air
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Poor ventilation
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Small leaks in door seals or windows
What excess humidity can cause
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Constantly foggy or icy windows
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Reduced visibility while driving (a serious safety risk)
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Mold and mildew growth
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Musty or sour smells
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Damage to upholstery, electronics, and interior trim
Most people try to solve this by blasting the heater or air conditioning. While that helps temporarily, it doesn’t remove the moisture source itself.
The Science Behind Salt: Why This Trick Actually Works
Salt (sodium chloride) is hygroscopic, which means it naturally attracts and absorbs water molecules from the air.
How it works in simple terms
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Salt pulls moisture out of humid air
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The absorbed water collects in the salt instead of lingering in your car
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Lower humidity = less condensation on windows
This is the same principle behind:
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Commercial moisture absorbers
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Dehumidifier packets
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Anti-clumping agents in food packaging
The difference? Salt is cheap, available everywhere, and reusable.
How to Use the Salt-in-the-Car Trick Correctly (Step by Step)
What you’ll need
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1 clean glass, bowl, or cup
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Regular table salt, sea salt, or rock salt (do NOT use iodized salt if possible)
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Optional: breathable fabric (sock, gauze, or mesh)
