If you drive frequently, you must have come across a common issue of car windows fogging up. While not a life-threatening problem by any means, such window fog can still interfere with visibility for the driver, leading to road mishaps.

Have you noticed how such things tend to happen when you crank on the AC?

Well, that is because water droplets accumulate on your car’s windows due to the difference in outside and inside temperatures.

Furthermore, the humidity in the inside and outside air also exacerbates this problem. If you are wondering how to clear fog from your windshield, read on.

What is the reason for Foggy Car Windows?

Glass car windows act as a surface for condensation, causing water droplet forming on them. Condensation is a process when water vapour or humidity contained in the air transforms into its liquid form after being exposed to a colder surface.

For example, think of a metallic container holding ice cubes. Due to this ice, the metal surface is much cooler than its outside atmosphere.

Therefore, when outside air touches this metal surface, droplets of water are formed. These droplets are known as condensates. The same principle applies to your car windows as well.

Before you can arrive at an answer to ‘how to get rid of foggy windshield’, you must understand how it is created. Let us assume that you are inside a car with its AC turned on.

However, the outside temperature is sweltering. Under such a circumstance, humid air from the outside touches the cold glass and immediately condensates on its outer surface.

Similarly, if air within a car were warmer than air outside it, this condensation would occur on the inner surface of a window.

Regardless of which side of the glass such a fog forms, your primary concern should be getting rid of it.

In the summertime, condensates form on the outer surface of car windows. To prevent such a thing from happening, you can employ one of these following methods:

• Reduce AC Temperature - Cranking up the AC inside your car during hot and humid summer days can feel good. However, such a habit aids in creating a distinct temperature difference inside and outside your vehicle. Thus, if you do not want a layer of fog on the windshield while you drive, dial down your AC unit. This will slowly increase inside temperatures to match outside mercury level.
• Crack Car Windows Open A Bit - If you can bear the summer heat while driving, the simplest solution to prevent fog formation on window glasses would be to roll them down a bit. As soon as outside air starts coming into the vehicle, internal temperatures equalise, thereby dissipating condensates. Still, this may not be an option for everybody, considering the blistering heat that some place of India undergoes during summers.
• Turn on Windshield Wipers - Perhaps the most obvious answer to the question ’how to remove fog from outside windshield’ is to power on the vehicle’s windshield wipers. If turning on the wipers seem to make things worse, you can spray some cleaners and then use the wipers instead.

In winter, this formation of fogs on glass windows is reversed. Instead of on the outer surface of these windows, droplets will form on the inside.

Since air outside at such times tends to be cooler than within your car, such a phenomenon takes place. Here are some ways to prevent this:

• Decrease Inside Temperature - Crank up your air-conditioning unit to match the outside temperature. This immediately stops further water droplets from forming on the glass surface. However, this added cold may not suit everyone. Drivers can offset some of the discomfort by carrying an extra layer of clothing with them.
• Turn on ‘Fresh Air Mode’ - Fresh air mode refers to a particular facility through which the car can circulate air from the outside without a sudden and drastic decrease in the inside temperatures. Instead, the inside temperatures are gradually equalised with the external ones. Doing so clears up any fog formation on your windshield and windows. While doing this, make sure that the recirculation mode is turned off, as this feature prevents external air from entering your car. Instead, this mode is for recirculating the air within the confined spaces of the vehicle.
• Utilise the Defogger Functionality - Look for a button marked with a square and three squiggly arrows pointed upward. This defogger button is immensely useful to drivers in extremely cold climates. Turning this on sends a blast of air to the inside surface of your car’s windshield. The air in question is at the same temperature as that of the air outside, thereby swiftly clearing up any foggy glasses. 

Besides the aforementioned methods, you can also implement these age-old techniques to prevent fog formation on your car windows altogether.

• Shaving Foam on Car Windows - Believe it or not, using shaving foam on your car’s windshield is a sure-fire way to eliminate foggy surfaces. Take a clean cloth and apply a coating of shaving foam on the windows with it. Make sure that this foam remains on the glass for at least 3-5 minutes. Then, use another dry cloth to wipe off the remaining foam residue. The shaving foam creates an invisible layer of protection on the glass, thereby preventing condensation from setting in. Don’t believe us? Try it out!
• Using Silica Balls - Silica balls absorb moisture from the air. Therefore, keeping a few of them inside a sock or other such cloth, and placing them on the dashboard should prevent fogging up of car windows. A dehumidifier bag also does the same job. If you can get your hands on one or more of these bags, keep them on the car’s dashboard.