How to defrost and defog your car windscreen quickly when it's cold and icy

Australia Broadcast Center

17-06-2025

If defrosting an icy windscreen has become part of your morning routine, we're here to help.
There are several dos and don'ts to making sure you safely defrost the glass, and get to work or school on time.
We also share the fastest way to defog your windscreen once in the car.
The easiest and most accessible way to defrost a windscreen is by pouring regular tap water over the affected area.
If the water temperature is above freezing, that will melt the ice.
You could use a water bottle or nearby hose, for example.
Be warned, using hot or boiling water is a mistake.
Rapid temperature changes can crack the windscreen's laminated glass.
If you prefer, a bank card or other plastic card can be used to scratch away at the frost.
You can also buy purpose-built scrapers (if you're fancy like that).
There are products on the market that involve various alcohols designed to quickly melt ice.
"There are ones for windscreens that involve various alcohols, things like propylene glycol," says Nathan Kilah, senior lecturer in chemistry at the University of Tasmania in Lutruwita.
Along with de-icer sprays, a solution of vinegar and water is a method of windscreen defrosting that is another example of this.
Dr Kilah is personally not a fan, though. He says the products can be corrosive and may end up causing problems.
If you dread the defrost chore on a cold winter's morning, you can prevent the icy windscreen in the first place.
Leaving a blanket, towel or cardboard on the windscreen is effective.
Experts say this means you can just "peel off" any ice crystals that have formed due to the temperature dropping off.
Our readers shared some of their more novel ways of defrosting their car windscreen, including parking a car "nudged" into some bushes.
One reader parks their car so it faces east to get the morning sun, while another pops a hot water bottle on the dash (not touching the glass) "before breakfast".
For electric vehicles, one reader suggests using the app to turn on heater before you brush your teeth.
And apparently half a potato does a good job of scraping off frost without scratching the glass!
To defog a windscreen from the inside, you can either heat up the surface to evaporate the water, or cool down the inside of the car, so it equilibrates.
While some people will opt for the latter by blasting cool air, Dr Kilah prefers to "turn on the heater and warm up the surface so that fog won't form".
If you don't have an air conditioner in the car, an anti-fog wipe or spray could be an option.
It's to be used ahead of time, before fogging occurs.
"These products leave a thin film of material on the glass that somewhat prevents the formation of water droplets," Dr Kilah says.
"But the products can require frequent reapplication or need pre-cleaning for them to work well."
You can also try opening the windows to lower the temperature of the air inside the car, though Dr Kilah warns "it won't be very comfortable."