How to Get Rid of Fog from Car Glass

Driving a car comes with a set of annoyances like getting stuck in traffic, people honking unnecessarily, drivers cutting into your lane, etc. These are that things where we have limited control.

But we can reduce on important annoyance- Fogging up of windows during summers, monsoon, and winters. We only give thought to this issue when the windows are actually fogging up. And then you can’t remember what to do.

When I encountered this issue recently, I had to force myself to think about condensation and evaporation science class. And even after reaching a good conclusion, it only made the fogging much worst. In the end, I reached for the microfiber cloth door pocket and wiped off the fog.

I thought this shouldn’t be this hard. So after reaching home I researched online to find the best way to deal with car windows fogging. I found several contradicting information but there was one that always works like a charm for me.

To remove winter fog from the windshield: Turn the heater on full blast, click AC button, turn off air recirculation, and crack open windows.

Why Do Windshields Fog?

The fogging happens when the glass of your car is cold and humidity is high in the air (outside or inside cabin). As the air carrying moisture contacts cold glass, water vapour start to condense over it. This is what we call fogging.

Defogging in Winters

The fogging happens on the inside of the vehicle when it’s cold outside. This happens because glass of the car is cold and when you sit inside the vehicle, the humidity condenses on the glass inside. Humidity of car cabin is high as we breathe out water vapors in our breath. Let’s see the best solution to clear up fogged up windows during winters:

Step 1) Turn the heater on full blast: Here’s a fun fact for you: hot air at 103° Farenhiet/40° Celcius holds over ten times more moisture than cold air at 36° Fahrenhiet/2° Celcius. So turn on heater on full blast so that air can hold more moisture.

Step 2) Turn on AC button: Turning the AC on will make the air pass over the cool AC coils. The dry air will enter cabin this way as condensations form on the cold AC Coils. Ever noticed a pool of water under your car? That’s the condensation from the AC coil.

Step 3) Turn off Recirculation (Get fresh air from outside): We learned before that cold air holds less moisture. We want to bring in this cold air and heat it up to increase its moisture absorbing capacity. So we will turn off the air recirculation.

Step 4) Open the windows sightly: Cracking open the side glasses helps in the exchange of hot air with cold air. This has an instant effect to clear fogging, both during winters and summers.

fog on the windshield
Foggy windshields are hazardous apart from being annoying.

Defogging Windshield during summers

The fogging happens outside the cabin during summers. This happens as air is humid outside and glass is cold. Let’s see how to deal with it:

1) Lower AC temperature (make it hotter): You need to make the temperature of windshield little higher as it’s the cold glass that’s causing the fogging. So lowering the AC fan speed and temperature would help.

2) Use Windshield wipers: Since the fog is collecting on the outside of windshield, you can easily use wipers to clear it up. Sometime, wipers might not run freely over the fog, so it’s a good idea to spray a bit of washer fluid too.

3) Open windows: Cracking open the windows helps in this case too as exchange of air reduces outer and inner temperature differences.

Defogging in Monsoons

Fogging can happen on the outside or inside the glass during rains. Air generally becomes more humid just after rain so outside air has more moisture which can start fogging up on the outer side of windshield if your glass is cold.

But it can also fog up the inside as the glass becomes cold due to rainfall. Cold glass plus humid air is perfect recipe for fogged up windows. The inside fogging increases if your clothes had become wet before getting in the car. Inside the car, the water from your clothes evaporates to increase cabin air moisture.

In either case, you know how to clear the fog. Refer to defogging in summer and winter section above.

No brainer things that you can do to help in either case: Turn off air recirculation, crack open side windows.

How to prevent fogging up of car windows

Wouldn’t it be awesome if car windows don’t even fog up? This is possible but you’ll need to prep the glass for this. There are several hacks and dedicated products that will prevent fogging on of car glass. Let’s discuss each of them:

1) Keep the glass clean: A clean glass is less likely to fog-up compared to glass that has dust and oils deposited on it. Dust particles attract moisture and when they do it condenses on the cold glass. A clean microfiber cloth and glass cleaner should take care of it. A glass cleaner is a must-have item for every car detailing kit.

2) Kitty Litter in Socks: Kitty litter helps absorb water from the air. Throw some kitty litter into socks and place it near the windshield. This will help make the air dry so that moisture doesn’t condense on the windshield.

3) Silica gel sachets: Like kitty litter, silica balls also absorb moisture out of air. That’s why you’ll find them placed in shoe box, bags and other garments. Just save those silica sachets and place a couple of them near car windshield.

4) Shaving Foam: This is one of the most convenient way to prep the windshield to resist fogging. Just spray some foam out of the shaving can onto the windshield and spread it around. Then leave it for 2-3 minutes and wipe off with a clean microfiber cloth. This process lays a very thin layer over the glass surface that resists fogging. This coating will lasts for few weeks, then you’ll need to redo this process.

5) Shine Armor Anti Fog: This is one of the most popular anti-fogging products on Amazon. This works similarly to the shaving foam method. But the coating lasts for a lot longer. Customer reviews seem to be pretty good so it’s definitely worth a try.

Checkout: How to remove dents and scratches from your car & remove tint from car windows

Siddharth Sharma
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Siddharth Sharma

Siddharth has always been passionate about Cars and Bikes. He was the kind of kid that always had the latest Auto magazine in his school bag. He had this dream- to become a professional racecar driver. Finally, in 2012 he found himself racing as a rookie driver in the Polo R Cup national racing championship. Over time he had to readjust the sail and get into automotive journalism to continue enjoying machines on wheels.