Why Do My Car Mirrors Fog Up and Freeze?
In order to stop your mirrors from fogging up and freezing, you need to understand why it happens in the first place.
The percentage of water vapour in the air varies between 0.2% and 4% depending on the temperature. As air temperature cools, the water vapour transfers to a liquid state when it hits the glass of your mirror and then sticks to it. The water molecules also stick to one another. When the temperature drops below 0°C, the stuck water will freeze on the surface of the glass.
Although car mirrors appear to have a smooth surface, they're actually covered in tiny indentations that the water can sit in. To keep the mirrors from collecting this water, you need to make their surface is less sticky and take advantage of how the water molecules stick together.
How To Keep Side Mirrors From Fogging Up
Dealing with mirrors that steam up is usually a task reserved for the bathroom. You can use the same tricks on your car mirrors that you would use to keep your bathroom mirror from misting up after a hot bath or shower.
RUB SOAP ON YOUR CAR MIRRORS
While the door mirror is clear from any water or mist, take a regular bar of soap and lightly rub it over the mirror, making sure to cover the whole surface.
Soap is "hydrophobic" which means it repels water. By coating your car mirrors with a thin layer of soap, the water molecules will be unable to stick to the surface and obscure your view.
NOTE: You can also use liquid soap or vaseline and it will have the same effect.
RUB SHAMPOO ON YOUR CAR MIRRORS
Pour a small amount of shampoo onto a folded paper towel and rub it all over your side mirrors. Then, using a clean paper towel, wipe the mirror dry. Make sure the mirror is completely dry, otherwise you'll end up with a blurry mirror which will make your vision worse.
NOTE: You can also use shaving cream, toothpaste or laundry detergent.
MAKE A VINEGAR SOLUTION
Using an empty spray bottle, create a mixture that is equal parts of vinegar and water (one cup of each will be enough to start with). Stir the solution until it's sufficiently mixed.
Spray the mixture directly onto a paper towel or cloth and apply it to your car mirrors. This method should last a couple of days, so if you notice the effects starting to wear off, continue to re-spray your side mirrors as necessary.
INVEST IN A SPECIALTY PRODUCT
Products such as Rain-X's Water Repellent are wax-based and have been specially designed for car mirrors to prevent fogging and provide you with optimum levels of visibility.
Using a soft dusting cloth or an old rag, place a small amount of the product onto it - don't try to apply directly to the mirror because any spillages could affect the car's paintwork.
Rub the wax thinly over the entire surface of both door mirrors. Then take a dry cloth and buff the mirrors until the reflection doesn't appear distorted by the product. The wax fills the mirror's indentations and causes the water to run into one big stream so that it falls down and off the surface.
How To Demist Car Mirrors
If you don't use any of the above methods to prevent your wing mirrors from fogging up, you will need a way to clear them before you start driving.
Although most people will use tissues or a sponge, the best thing to use is actually a chalkboard eraser. You can also use this to clear your windows if they're steamed up as well.
How To Keep Side Mirrors From Freezing
When there's water on your car mirrors it will freeze on the surface if the temperature drops below 0°C, leaving you to scrape ice or frost off your side mirrors in the morning.
To prevent this from happening you need to keep the mirrors warm which isn't realistic. Instead, you can stop water from gathering on the side mirrors and being exposed to freezing temperatures.
Using a carrier bag (or something similar), cover the door mirror and secure it with a hairband or elastic band. When you come to your car in the morning, your wing mirrors will be ice-free.
How To Unfreeze Car Mirrors
If you forget to cover your side mirrors before a cold night, it's likely that they'll be covered in frost and ice in the morning.
The quickest way to remove this ice is by warming the door mirrors up. Some cars come with heated wing mirrors that can be turned on from inside the car.
If you're not fortunate enough to have this feature, you should invest in some de-icer and a car scraper. It's important to dry the mirror before you set off on your journey to prevent it from fogging up while you're driving.