It must have happened on more than one occasion. They are driving and suddenly the windshield begins to fog, sometimes even very quickly, creating in this way a situation of potential danger due to lack of vision. Why this phenomenon happens? How can we solve it?
Firstly, to understand why fog is formed in the windshield we have to make clear a few concepts. In the atmosphere, among many other gases, there is water vapor, which is still water in the gas phase. The amount of water vapor that a given mass of air can contain depends on its temperature. Specifically, warm air may contain more steam than dry, to the extent that approximately that amount of steam doubles as the temperature rises to 10 ° C. This property is key to understanding the formation of clouds and rain, since when a mass of air rises and cools, as each time may contain less steam, there will come a time when it is saturated, that is, where Can no longer contain more water vapor.
Let’s go back to our car and imagine a cold winter day in which we drive with the heating on. Inside the cabin, the temperature will be pleasant, and due to the steam we exhale when we breathe, the humidity inside the car will also be elevated. But outside it is cold, and the glass of our car, in contact with the outside, will have a much lower temperature than the interior of the car. In this way, the air inside the vehicle that comes in contact with it, will cool quickly, thus reducing the amount of water vapor that can contain, until, being unable to contain more, when cooled enough to Is saturated, will begin to condense in the form of mist on the cold windshield.
And, what can we do to get rid of that fog that can even cause an accident? Well, a simple trick is to connect the air conditioning and direct it towards the glass (with the heating on if you prefer, not to freeze us from cold). Air conditioning is a very dry air, an air therefore, which, according to the expression, “can fit” a lot of water vapor in its breast. In this way, just as the dry air dry the clothes very quickly, dry air conditioning will remove that mist from the surface of the windshield (if our car does not have air conditioning simply down the windows to enter cold air Exterior). Something similar can be done in the bathroom after showering: if we direct the warm dry air of the dryer towards the glass, the mist will disappear as if by magic.