To keep windows from fogging up: the rules of transparency

To keep windows from fogging up: the rules of transparency

Poor visibility is a very common cause of traffic accidents. However, it is not always provoked by fog or heavy rain, with which “fog lights” and “wipers” quite well cope. But misted glasses may become that very stumbling block, which your “horse of steel” will stumble on. And if your car is missing windows and other major parts, turn it in for recycling:

There is a concept about which few people know, but each driver faces. It is so-called “dew-point”. In layman’s terms, it is the temperature to which air with a certain amount of water vapor has to be cooled for it to begin to condense. If the temperature of the glass in the car is about the same as the ambient temperature, the windows remain clear and transparent. But if its temperature is below the dew point relative to the air in the cabin, then the windows become cloudy as a result of fogging.

Causes of window weeping

So why do our cars have fogged windows? The causes may be different, but the main is the difference in temperature conditions outside and inside the cabin. The warmer air inside the car contains moisture, which when it hits the cold glass turns into microscopic particles of water, which refract light, thereby creating an effect that we call a fog. Simply put, fogged glass becomes a consequence of the very real fog that forms in the cabin.

One more enemy of glass transparency is the most different damp things, which can be found in auto salon: shoes, clothes, upholstery, mats, cloths, umbrellas, moisture-soaked noise isolation, etc.

Strange as it may seem, but glasses may “sweat” also in that case, if you are the happy owner of the automobile with climate control. If the system is normal, you will not have any problems. But when the special hole for moisture drainage in the system is clogged, the excessive condensate, which has nowhere to go, will fog your eyes.

One more malfunction which causes window misting is a coolant leak from a radiator or heater branch pipes straight into interior.

And finally, one should not write off drunk passengers or, Zeus forbid, the drivers themselves, whose breath automatically turns into alcoholic fumes. If you were in love with your chemistry teacher and listened to every word she said, you know very well that alcohol is an excellent absorbent, which absorbs moisture better than the hot sands of the Sahara. That’s why we are so unbearably thirsty in the morning after a raucous party. That’s why drunken people greatly accelerate the process of window fogging.

Methods of struggle against the “foggy” enemy
So, we have solved the reasons, therefore we shall proceed to the main thing – the ways to prevent formation of treacherous fog on glasses of your car. Proceeding from the first cause of window misting, it is necessary to take into account that it is possible to cope with it by airing or warming up a salon. The first method will be suitable for warm seasons, and the second will be just right for winter. It is possible to bring out windshield and side glasses from coma, blowing them by streams of warm air from a heater. A separate heating is provided for rear window. As a preventive measure, the driver and passengers should shake off moisture or snow from clothes. It will be useful to buy rubber mats instead of felt mats, which do not absorb a moisture at all.

There is an alternative way to resist window fogging in your car, but you will hardly like it if frosty and prickly winter is raging outside the car window. But in any case, in the fight for safety all methods have the right to exist. Try to equalize the temperature inside the salon with the temperature outside. That is just open windows. Only faulty air inlets can push you to do that, therefore try to eliminate the breakage, if you do not want to become a member of Bering Gulf walrus society.

Another way is to trust the modern chemicals, which are designed to fight against fogging of glass. The principle of their action is based on creating an imperceptible film that prevents the appearance of water droplets. It is sufficient to spray the composition and wipe the glass with a soft cloth. Experienced drivers advise not to treat the rear side windows, so that the “fog” is formed on them. There are only two groups of antifoggers. If some of them do not allow the formation of moisture, the others simply repel it.

Sometimes the windows in the car get very misty because the air intake flap from the street is defective. When it is closed, the same air circulates in the cabin, from which the moisture simply has nowhere to escape, except to settle on the windows. An easy way to check the damper is to spray something scented on the outside air intake. If the damper is working properly, you’ll smell that aroma in the car interior.

In addition to all of the above, you can upgrade the air duct that is located in the trunk. To do this, cut a hole in the side trim of the trunk and install a plastic grille – it will increase the outflow of moist air. Ventilating your car’s interior effectively will ensure that your windows sweat much less.


Researchers at the Massachusetts Institute of Technology solved the problem of window fogging with the help of modern technology. Thus, they created a special coating made of an ultrafine composite material which includes silicone and plastic. This coating is designed to attract water droplets and align them, turning the fogged layer into a transparent one. The development has attracted the interest of many car manufacturers. At the same time, the British company McLaren is going to replace in the near future “wipers” on all its models with a special technology that will clean the glass with ultrasound. We only have to wait for the future to come into its own.
Today we have tried to answer the question of why the car windows mist up, and how to deal with it. We hope that our advice will help you, because the only vehicle in which even with misted-up windows you can feel in complete safety is T-90 tank.

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