How to Defrost Your Windshield Fast and Effectively

Discover effective strategies for quickly and safely defrosting your car’s windshield, along with preventative measures to keep frost at bay.

Frost on windshield of a car

Most of you who live in areas where winter brings sub-freezing temperatures will struggle with the same recurring problem: a frost-covered windshield welcomes you after your car has been parked outside on your driveway or on the street all night. Most commonly, this icy mist cover is situated only on the inside of your windshield, but in some cases, the outside of your windshield may also be affected. This easy guide will show you how to swiftly and safely defrost both the inside and the outside of your windshield and it also hands ways to prevent it from frosting again. 

Understanding Why Your Windshield Frosts Up

Frost on your windshield is more than just a nuisance; it’s a natural phenomenon that occurs under specific conditions: 

 

  • When the temperature drops, especially on clear, cold nights, the warmth and moisture from your car’s interior (carpets, seats,…) evaporates. As the warm, moist air inside your car meets the cold windshield, it cools rapidly, and the moisture condenses on the glass. If the outside temperature drops below freezing, this condensation turns into frost. 
  • Frost that forms on the outside of your windshield on the other hand, is caused by the 3 C’s: Cold freezing air, Clear skies, and Calm conditions overnight. When the 3 C’s are present and humidity is high enough, millions of tiny droplets will descend on your car’s windshield, freeze and form a frost blanket that covers your windshield.

 

Factors like humidity levels, whether your car is parked in an open space or under trees, and even the cleanliness of your windshield can influence frost formation. 

Let’s explore some useful tips and tricks to remove and prevent frost on your car’s windshield:

How To Defrost Your Windshield:

Use Your Car’s Heater and Defroster

 

  • Start your engine, manually or with its Remote Start, and activate your car’s heater, AC and defroster. 
  • If you’re unable to get into your car because your car doors are frozen shut and your car has no remote start, here’s how to open them without causing damage.

    If your car is equipped with a remote start function, make sure to always park it with the heater, blower and AC on maximum setting and the defroster on in winter. When you’re unable to open your car doors, you can start your car remotely to heat it quickly and melt the frozen doors to get them unstuck.
  • Turn on the rear window’s defroster (it will be frosted too) and turn the heater’s temperature to the hottest setting with the blower at full force and the AC on. Select windshield demisting mode if possible. This warms the windshield from the inside, but it will melt the frost both on the inside and outside.

    The AC system will act as a dehumidifier, removing moisture from the air so no new frost will form on the inside of the windshield. Turn off the recirculation mode to allow drier outside air to enter, enhancing the defrosting process. This prevents the humid air recirculation in the car, especially if your car is not equipped with AC.
  • Do not use your windshield wipers to clear the frost from the outside of your windshield until you have checked that they are unstuck and most of the outside frost has melted, because those millions of tiny frost crystals can be sharp like sandpaper and they might damage your windshield wiper rubbers, making them less efficient. 

Apply De-Icing Fluids

 

  • Use de-icer spray for quick frost removal. Spray it on the outside of your windshield and wait a few moments before wiping. It is not recommended to use de-icer spray on the inside of your windshield, because it has a high alcohol content that is unsafe to spray in confined spaces and it may also damage your car’s interior.

    You can however, moisten a small towel by spraying de-icer spray on it in open air and then use that towel to wipe off the frost from the inside of the windshield in a controlled way, with minimal exposure to the spray mist and no risk of damaging your car interior. You want to do this with your car doors open to allow fresh air to circulate.
  • You can also make your own homemade de-icing fluid to defrost the outside of your windows without heat. Mix 2/3 of isopropanol ( isopropyl/ rubbing alcohol) with 1/3 of (distilled / deionized) water.

    Pour this mixture into a spray bottle and apply it to the windshield. This solution will melt the frost and it will not freeze due to the alcohol contents in it.

    Just like with commercial de-icer sprays, you can moisten a small towel with your home-made solution and use that towel to wipe off the frost from the inside of the windshield in a controlled way, with minimal exposure to the vapor and no risk of damaging your car interior. Again, you want to do this with your car doors open to allow fresh air to circulate.
  • We do not recommend using a vinegar / water mix because vinegar is an acid and is highly corrosive.
  • Use Hand Sanitizer: If there is no de-icer spray or rubbing alcohol available but you have access to hand sanitizer liquid or spray, its high (70-80% isopropanol) alcohol content can effectively melt ice too. Spread sanitizer liquid directly onto the frozen windshield or preferably spray it on.

 

Use a Hair Dryer

 

  • If your car is parked in front of your house and you have access to an electrical outlet near your car, a hair dryer is your tool of choice to de-ice your windshield in a hurry. 
  • Set the dryer to its highest setting and direct the warm air onto the frozen windshield. 
  • You want to warm the windshield gradually and evenly, because concentrated heat might crack it.

 

Pour Warm Water 

 

  • Arguably the quickest but most risky way to unfreeze a frosted car windshield is by pouring luke-warm (not hot) water over it. You have to ensure the water is not boiling hot, as extreme temperatures can cause rapid, uneven material expansion. This big temperature difference can shatter car glass. Gently pour the warm water over the entire windshield as evenly as possible.

    Again, the water should be luke-warm and you want to pour it evenly and gradually, to not cause localized rapid temperature changes.

    If performed hastily or incorrectly, you might crack your windshield!
    This method is not for the faint-hearted!
  • When the ice has melted, immediately activate your (unfrozen!) windshield wipers while spraying winter windshield wiper fluid to keep the water on the windshield from freezing again. 

 

Use an Electrical Windshield De-icer

 

  • Electrical windshield de-icers are small dashboard-mounted electric automotive appliances that are specifically designed to melt a frosted or iced windshield quickly by blowing warm air directly onto it from the inside of your car. They are plugged into the cigarette lighter socket and heat immediately when you switch them on, unlike your car’s heating system, which will only start warming your windshield after your engine heats up.

 

Scrape Off the Frost

This is the method we recommend the least for a thin frost layer, because it’s a lot of elbow grease for a messy result. You’ll end up with a powdery mess that still will have to be removed / brushed off. You will notice that it’s near impossible to scrape the frost off entirely without leaving some frost streaks and spots. It’s also very difficult to see what’s what between all that loose frost powder.

If you still want to have a go, here’s the most efficient way to do it:

 

  • Employ a plastic ice scraper for stubborn frost. Avoid metal scrapers to prevent glass scratches on your car windows.
  • Begin scraping from the edges towards the center.
  • Brush away the loose ice powder using a snow brush and scrape off remaining frost.
  • Check that your windshield wipers are unstuck before activating them. Then, simultaneously activate your windshield spraying system to thaw any remaining ice or frost and to lubricate your windshield wiper rubbers to avoid damaging them. Make sure there’s winter windshield wiper fluid in the spraying system’s reservoir, otherwise the fluid will freeze again.

 

How To Prevent Your Windshield From Frosting

Outside Windshield Frost Prevention:

 

  • Apply a Protective Coating: Use a windshield treatment to create a protective layer that repels water. It only takes a few minutes to apply and helps against frost buildup.
  • Use a Windshield Cover or Car Cover: A specifically designed, insulating windshield cover will prevent frost from forming. So does an outside car cover.
  • Park Under a Carport or Tree: Parking your car under a carport or a car tent will protect your car from water or snow icing up your windshield. Parking your car under the cover of a large tree may help also.

Inside Windshield Frost Prevention:

 

  • Apply a Protective Coating: Use a windshield treatment to create a protective layer that repels water and helps prevent frost forming. It only takes a few minutes to apply and helps against frost buildup.
  • Keep the Car Interior Dry: Remove snow and ice from your shoes and clothes before entering the car to reduce interior humidity.

    Regularly check the waterproofness of your car’s door-, sunroof- and boot- seals by inspecting the surrounding  floor carpet for moisture. Water ingress causes humid carpets and evaporation, which in turn causes a fogged and frosted windshield.
  • Use Moisture Absorbers: Silica gel moisture absorbers placed inside your car can help keep humidity low.
  • Regularly Clean the Inside of Your Windshield: Oils and dirt on the inside of your car’s windshield attract moisture. Regular cleaning with a professional non-streak glass cleaner spray helps prevent this. A combined clean & repel spray not only cleans, but also helps repel water, which in turn keeps frost at bay.

Do’s and Don’ts:

 

  • Do: Cover your windshield with an insulating windshield cover or an outside car cover when parking outside in winter.
  • Don’t: Pour hot water on your windshield, as it can lead to cracking due to rapid temperature changes.

Conclusion

Frost is formed when a sudden temperature drop from above to below freezing temperatures causes warm(er) humid air to freeze onto cold objects like your car’s windshield. It can form on the outside as well as on the inside of your windshield. Knowing how to quickly and safely remove frost is essential to maintain clear visibility on the road at all times. 

Therefore, understanding and managing frost on your windshield is an essential part of safe and comfortable winter driving. Remember, a clear windshield is not just about comfort; it’s a critical safety measure to prevent accidents caused by impaired visibility. By following the guidelines outlined in this guide, not only can you effectively remove frost, but you can also take proactive measures to minimize its occurrence. Drive safely and enjoy the winter season with a clear view of the road ahead.

Happy cruisin’!

Be Safe!

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