Right Driver

The quickest way to defog or demist your car’s windscreen

You come out to your car on a cold morning and the inside is completely fogged. You can’t see where you’re going, and when you do wipe a clear patch (barely big enough to see out of), it begins to fog again with your breathing. Breathing creates humidity, and it’s the water-rich air condensing on the cold surface that causes the fog.

View of the road from the fogged glass of the car

What’s the solution? Certainly not holding your breath. The best plan is to dry the air. Here are the steps to get the quickest demisting action in your car:

  1. Always carry a large, clean lint-free cloth for cleaning and wiping the windows (a window that’s dirty on the inside will fog up much quicker).
  2. Always use the air conditioning set on outside, not recirculate, for rapid demisting
  3. Always put the fan on maximum, and point the vents towards the windscreen
  4. Always use the maximum heat available as this will evaporate the condensation much more quickly
  5. If it’s not raining, open the windows to let fresh, drier air into the car
Front windscreen demister

You may have a button that changes the fan speed to maximum, turns on the air conditioning and redirects air to the windscreen. You’ll need to change the temperature and open the windows yourself.

If there’s snow or ice on the outside of the windscreen, work on defrosting that first or the extreme cold on the screen will make the condensation issue worse.

Rear windscreen demister

The rear demister is usually a rectangle. This passes power through a series of fine wires that are either stuck to the glass or embedded in it. This warms the glass and evaporates the condensation.

Darren has owned several companies in the automotive, advertising and education industries. He has run driving theory educational websites since 2010.

Posted in Advice