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Foggy Windshield: How To Remove Fog From Car’s Windshield

By 12 Mins Read

You might have already come across foggy windshields at certain times, especially during rainy days. This happens as a result of hot air contacting cold air. This can be interpreted on warm days, as warm air from outside meets the air-conditioned cold air inside the vehicle. This happens on all parts of the body of the vehicle. This occurrence especially on the windshield and windows obstruct the driver’s vision. Thus, it can cause dangerous situations while driving. It requires stopping the vehicle, getting out, and wiping the windshield every time the fog is created. This is a very difficult and time consuming task while traveling. Despite this, there are ways to remove the occurrence of foggy windshields effectively. Let’s learn more about this.

Fog and Moisture

When the humidity in the air turns into tiny droplets of water, then the fog materializes and comes into existence on the windshield. This is not a surprising or strange phenomenon. This is completely natural in extreme weather when there is a considerable temperature difference between the surroundings and the inside of the car. Cold air is dry. The moisture that is trapped in cold environments gets frozen and hidden in fabrics or on various surfaces. For instance, when you enter a warm car in winter, you bring hidden moisture along with you. This would get unfrozen inside the warm car. Even the steamy air you exhale would produce moisture. 

It’s Physics!

Warm air has more energy and this energy makes water molecules in air move faster and further apart from one another. This energy is also the reason for the evaporation of moisture in the car and fills the air with more vapor. The reverse action occurs when the warm air inside meets the cold window. The hot air inside loses its energy and water molecules would slowly condense into droplets of water. These droplets stick to the glass and create a fog that blocks the view. The fog occurs when the monstrous air hits the window that has dropped below a certain temperature. This is called the Dew Point.

A foggy windshield would occur due to few main reasons:

  • Humidity

Humidity is a form of water turning out into water vapor. The air that comes out when exhaling contains humid air. When there are many people inside the car, then fogging would tend to be more of a problem.

  • Heat

Temperature is energy in moving molecules. Moisture is high in warm air than in cold. Since this is not any form of a chemical reaction, the moving energy of molecules does not keep holding to the water molecules. Water becomes gas when heated. Thus, more space is created between the molecules with warm air and water molecules can be fitted into this space.

  • Surface Tension

Water molecules tend to attract other water molecules and form tiny droplets opposing the glass surfaces.

  • Condensation

When hot air rich in moisture contacts the cold windshield of a car, condensation occurs. This is the process of moisture converting to liquid water. This happens mostly in the early morning. In the situation of 100% relative humidity and if the temperature reduces further, the water needs a way to get out. This is why you see moisture in the form of fog or dew on the ground. This occurs when warm air with moisture contacts the ground which is cold.

How to Remove Fog from Car Glass during summer?

Even though staying inside a cool car is more appealing in hot weather, it can be dangerous due to the formation of fog. Usually, the fog created in summer is easier to be removed. 

To reduce fogging, increase the temperature inside the car by reducing the power of air conditioning. When the temperature increases and matches the outside temperature, the fogging would stop quickly. 

Another thing that can be done to reduce foggy windshields is to open the window a little and allow outside air to enter inside. This would balance the temperature quickly and remove the fog while you can still feel the cool air.

You can also get rid of fog that occurs in summer by turning on your vehicle’s windshield wipers. Of course, condensation or fog is basically water and you can use vipers to wipe off the fog. If it does not work properly, you can try spraying some cleaner and then turning on the wiper to a lower setting. This would clean off the fog well.

Another thing you can do is completely open the windows. After all, safety is more important than comfort, right? This might be the easiest and fastest way to defog the windshield. Roll down the windows to a preferred height and allow outside air to come in.

How to Remove Fog from Car Glass during winter?

During winter, cold air from outside contacts the warm air inside the vehicle and creates condensation of fog. Here, the fog is created from inside of the windshield. This is comparatively difficult to be removed. However, there are ways to remove car windows fogging up inside.

There is a “Fresh Air Mode” button on the dashboard that has a car with an arrow pointing towards the car. When this is turned on, fresh air is pulled from outside into the car. But this does not reduce the temperature inside the vehicle. The temperature is balanced enough to remove the fog from the windshield. Make sure that the “Recirculation Mode” (which has a car with a circular arrow inside it) is turned off. It would make the air inside the car recirculate by closing the front air ducts.

Also, you can try reducing the temperature inside the car and allow the fogged up windshield and windows to clear out. However, this would make you feel quite uncomfortable with the cold.

There is a defogger button with a box and three squiggly arrows pointing upwards. This is very handy for vehicles that travel in extremely cold climates. When this button is turned on, air is sent to the windshield. This air would match the temperature of the surroundings and makes the fog disappear from the windshield. Some cars have these defogger buttons for both front and rear windshields.

Another hack you can try for a quick fix is to first turn on the heat to its maximum as hot air contains more moisture. Then turn on the air conditioner so that it would pull out the moisture from the air and pass it over the cooling coils. Then turn off the recirculation to make cold and dry air get into the vehicle. Rolling down the windows and opening up a bit would also help in giving out the humid interior air and getting in some dry air from outside.

Prevent your windshield from fogging in the rain

It would on rainy days that you would be wondering how to get rid of fog on the windshield. Of course, there are ways to avoid car windows fogging up inside which obstructs the vision on rainy days. Let us identify this in detail.

Why Does Rain Cause Fogging?

The condensation of moisture on the inner surface creates windshield fogging. So, wiping outside using wipers would not help to reduce the fog during rain. This happens due to high humidity inside the vehicle and cooler air outside than the inside. This is similar to the occurrence of water droplets on the surface of a cool drink container.

How to Get Rid of Fog?

The easiest way would be to increase the air conditioner and make the inside as cool as the outside or even more. You can also use a lint-free cloth to clean the moisture before turning up the A/C. Another option to make this happen faster is to turn the A/C so that cold air blows directly on the windshield.

What If The Fog Doesn’t Disappear?

A reason for the difficulty in removing fog would be having oil mixed with moisture. This creates a smidge on the windshield that is hard to be removed. This oil may be something that comes from a cleaning product used to clean the surfaces, or even from an air freshener used in the car. During hot temperatures, some air fresheners leave oil particles in the air, which then would get contaminated on the windshield. This can be cleaned off by using some rubbing alcohol or soda. Apply a bit of this on a soft cloth and rub it across the oiled area on the windshield.

Tips to Prevent Car Windows from Fogging Up

If you want to get rid of fog, there are some useful tips that would come in handy in the future. You can do these easily with products that are easily available. You can use the following tips and hacks next time you get foggy windshields to ensure a clear glass easily. Driving with a clear vision is very important for the safety of everyone.

  • Clean Glass

The most successful way would be to keep the glass clean at all times. Dirt particles or oil would act as magnets for moisture. It holds moisture and doesn’t let go easily even when wiped off. 

  • Anti-Fog Products

For long-lasting effects, anti-fog coating products can be used. Before applying these products, make sure that the windshield is clean and dry.

  • Dehumidifier Bags

Place one or more dehumidifier bags on the dashboard near the windshield. There are silica balls inside these bags which absorb moisture from the air. In case you have difficulty in finding dehumidifier bags, you may use few silica balls placed inside a sock. You can keep them in the car to absorb moisture.

  • Shaving Foam

Shaving foam can also be used for this. Apply a handful of shaving foam across the glass using a clean cloth. Keep the foam for about two minutes, and then wipe it off with a clean cloth. Make sure not to leave any residue behind. This helps to create a protective layer on the windshield and prevents moisture collection.

  • Ammonia-Based Window Cleaner

Cleaning the interior of the windshield using ammonia-based window cleaner can remove any build-up formed inside the windshield. Make sure to use horizontal or vertical strokes when applying the window cleaner. Apply the window cleaner regularly to the inside of the windshield. However, ammonia-based window cleaners would not be suitable for window tints, if you have installed any. Please refer to Window Tint Aftercare Tips to learn more on this.

  • Clean Shoes

Before getting into the car, wipe your shoes using a dry rag. Remove any water, dew, or snow on the shoes before entering. This would help in reducing the amount of water and moisture that gets into the car with you. Hence, the risk of a foggy windshield will also be reduced.

  • Inspection of HVAC System

The Heating, Ventilation, and Air Conditioning (HVAC) system’s malfunction could also result in difficulty of fog removal from the windshield. When the defroster is activated and if you notice that the windshield is fogging, then you should take your vehicle to an auto body repair shop for consultation.

  • Check Your Weather-stripping

The weather-stripping on the doors and windows of your vehicle might have deteriorated. This would allow moisture to get inside the car. If there are any damp areas inside the car that would mean that you need to replace your weather-stripping immediately.

  • Preheat Your Car

Apart from parking inside, you can preheat your car with an interior heater to prevent fogging. This ensures that the windshield and other interiors have a high temperature at the very start. Therefore, if any humidity is encountered, it can be let out by opening the windows for a small time.

Would Fog Occur Due to Mechanical Issues?

Cars built after the year 2000 have cabin filters. This collects dust, pollen, and other tiny debris contaminants which help in quality air regulation inside the vehicle. The air conditioner is also filtered through the cabin filter. Filling up of excess debris inside this cabin filter would affect the performance of the defroster in the car. Thus, the air quality inside the vehicle would be reduced. As a result, the windshield gets susceptible to condensation and would create a fog over it.

Do Chemicals in Car Cause Fog?

Fog can occur due to contamination brought into the car. These small air freshening compounds inside the car are the most offensive ones. You are recommended to remove them if you have trouble with fog. Using air fresheners would be to deal with creating a better scent inside the car. However, instead of using these, you can enhance the hygiene of your car and avoid any bad odors. 

Car cleaners made to coat vinyl and plastic also create contaminants that result in creating fog on the windshield. It is better to avoid using these. These cleaners may not be effective and it is always better to clean the interior of a new vehicle simply with a clean wet cloth. These chemical cleaners, in spite of being known for creating a shiny appearance on the vehicle’s windshield, are most likely to leave behind a coating on the glass. These chemical cleaners would also have an impact on the window films that you might have installed. To learn more about the peeling off of car window tint, refer to Fixing Tint Wrinkles.

In addition to this, new vehicles create gases out of Volatile Organic Compounds (VOCs). These gases are created from the new plastic, fabric, and leather in the upholstery of the new car. When fresh air does not enter the vehicle or when left overnight, this occurrence of fog coating can be observed. This is because those gases cool and condense on the windshield and window glasses. However, after some time, these solvents and VOCs are baked out from the heat. Thus, it would be easier to keep the vehicle’s windshield clean. Keep a window cleaning kit and practice using it for five minutes every week. This would help to keep the windshield and windows clean and reduce the retaining of fog coating as much as possible.

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