The idea behind the salt trick comes from a property known as hygroscopicity, which describes a substance’s ability to attract moisture from its surroundings. Ordinary table salt can absorb water vapor when humidity becomes sufficiently high, particularly when the relative humidity reaches approximately 75% at room temperature. This means salt may interact with moisture in a damp environment, but it does not continuously absorb large amounts of water under all conditions. Although the concept has some scientific basis, a small glass of table salt is unlikely to make a significant difference to the humidity inside an entire vehicle.

Foggy car windows are usually caused by warm, moist air coming into contact with colder glass. This commonly happens during winter, rainy weather, or when passengers enter a vehicle wearing damp clothing. Moisture can also accumulate from wet floor mats, umbrellas, snow-covered shoes, or water leaks around doors and windows. When the humidity inside a vehicle rises, condensation may form on the glass, reducing visibility and making driving uncomfortable. Some drivers hope that placing salt inside the car will reduce this moisture, but there are more effective ways to address the problem.

One of the best solutions is to use the vehicle’s heating and ventilation system correctly. Turning on the windshield defroster, activating the air conditioning when available, and bringing in outside air can help remove moisture and clear condensation. It’s also important to keep the interior dry by removing wet items, cleaning damp floor mats, and checking for leaks. For vehicles that frequently experience excess humidity, a purpose-made automotive moisture absorber containing silica gel or another suitable desiccant may be more practical than loose table salt. Any moisture absorber should be secured so it cannot spill or interfere with driving.

There are also reasons to be cautious about leaving an open glass of salt inside a moving vehicle. A loose container can tip over during sudden braking or sharp turns, and spilled salt may contribute to corrosion when it comes into contact with damp metal components. Salt is not a reliable solution for mold or unpleasant odors either, particularly when the underlying source of moisture remains untreated. While this inexpensive household trick may sound appealing, understanding the cause of condensation is far more useful than relying on a viral shortcut. Sometimes the simplest solution isn’t adding something to your car but removing the moisture that’s already trapped inside.

🚗 Have you ever tried putting salt, rice, or a moisture absorber inside your car to stop foggy windows? Did it actually work? Share your experience in the comments!