How to quickly deice a car windscreen: The quickest and easiest ways to defrost and demist your car

Iced-over windscreens are the bane of many drivers' lives during winter, delaying departures and forcing them to stand in the cold scraping frost from the glass.

It might be a cold and boring task but it's vital to clear your car's windscreen of snow and ice before seting off. Failing to do so is dangerous and illegal.

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So here are some simple steps to quickly and safely defrost the outside of your car and defog the inside, plus some tips on how to prevent the problems in the first place.

Don’t use hot water

Every driver should know by now not to use boiling water on frozen glass. The rapid change in temperature is enough to crack or shatter a windscreen, especially if there is existing damage such as a chip or scratch. You should avoid even warm water for the same reason. And if it’s particularly cold, adding more water could see it refreeze before you’ve had a chance to clear the ice.

Start your engine

First, check your windscreen wipers are off. They can freeze in place and starting the car with them switched on could damage the wipers or motor. Once you’ve started your engine, activate your heated rear window and, if you have them, heated front screen and mirrors.

Turn the heating up and the air con on. (Photo: Shutterstock)Turn the heating up and the air con on. (Photo: Shutterstock)
Turn the heating up and the air con on. (Photo: Shutterstock)

Set the fans to blow warm air on the windscreen and make sure the air conditioning (if you have it) is switched on. This will help warm the glass gently to melt the ice on the outside and help clear condensation on the inside of the screen. The air con helps remove moisture from the air to clear the glass quicker. Don’t use air recirculation, this just traps the moist air in the car.

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Clear any snow

Use a soft brush or something similar to clear all loose snow off your car, including all the windows, roof and number plate. It’s illegal to drive with impaired vision or with snow which could fall off your car and cause a hazard for other drivers.

Use a proper ice scraper

While the car warms up, start scraping the ice but don’t be tempted to cut corners and use something other than a proper scraper. Credit cards and CD cases are less effective than a purpose-made scraper, more likely to break and could even scratch the glass. Don’t use your bare hands either. Jewellery can scratch the glass and your hands will leave grease marks, hampering your view. The same is true when clearing condensation from the inside, so use a cloth to clear any water from the glass.

Spray away

You can buy chemical deicing sprays but these aren’t great for the environment or your car’s paintwork. Instead, you can make up your own solution to help cut through the ice. Mix 1/3 of a cup of water with 2/3 of a cup rubbing alcohol and apply this to the frozen area, ideally through a spray bottle. Rubbing alcohol freezes at -89C, so should cut through the ice easily.

Homemade deicer can be just as effective but less harmful than shop-bought chemicals (Photo: Shutterstock)Homemade deicer can be just as effective but less harmful than shop-bought chemicals (Photo: Shutterstock)
Homemade deicer can be just as effective but less harmful than shop-bought chemicals (Photo: Shutterstock)

Stay with your car

If your car is parked on the street it is illegal to leave it unattended with the engine running. Even if it’s on your own property you shouldn’t step away from it, an unattended car with the engine running is an easy target for opportunistic thieves.

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How to prevent your windscreen icing or misting up

Prevention is better than a cure so to make life easier you can take steps in advance to stop your car windows icing up.

Parking in a garage or under shelter is the best solution but if you can’t do this try parking as close to your house as possible to provide some shelter from the elements.

If you car is parked outside use a cover on the windscreen. You can buy purpose-made ones or use a large sheet of cardboard or a towel/blanket soaked in salt water and held down by the wipers. Don’t use newspaper as this is too thin and will just stick to the glass. Try wrapping plastic bags around the mirrors to give them some protection.

To help stop ice forming in the first place, you can apply a homemade mixture of two parts white vinegar and one part water to the glass. The lower freezing point of the vinegar should help stop ice forming.

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To stop condensation in the car you should avoid leaving any wet items in the car. Also keep the glass clean, as this means there's less dirt particles for moisture to stick to. Odd as it sounds, try rubbing shaving cream on the glass. Rub a small amount over the glass with a cloth then wipe it off thoroughly. The chemicals in the foam leave a coating that helps stop moisture sticking to the screen. If the situation is really bad you can get dehumidified kits but for a cheap alternative, try a small tray of rice or cat litter to soak up some of the moisture from the air.

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