Car windshield defrosting: Why using hot water is never a good idea
(By Faizan Arif) We are in the midst of winter and every morning seeing your car’s windshield covered in frost won’t be a new thing for you.
There are many ways to remove the ice from the windshield. Some do it by scratching it off, some do it by pouring hot water and some may even be doing it the right way. But ever thought what hot can do to your windshield? There is a possibility of it cracking or shattering glass due to the sudden change in temperature. Not only this, but it can also damage the paintwork.
Pouring cold water is also a bad idea, as it can freeze on the glass and make matters worse sometimes.
The Science Behind it: Why it happens?
Generally, when the temperature of a material is increased, it expands. Glass is no exception to that. When you pour hot water on a glass, its outer layer will absorb heat. So, the outer layer will expand. Since glass is not a good conductor of heat, the conduction of heat through the glass layer is slow. Hence, the outer layer of the glass is hot while the inner layer is still relatively cold.
This temperature difference will cause the outer layer of the glass to expand significantly more than the inner layer. This difference in the amount of expansion exerts a tremendous amount of pressure on the glass. If the glass is unable to hold up against the large pressure, the glass will crack. If the water is really hot, the glass will definitely crack.
In short, glass expands at a quick rate only in spots where the hot water is splashed while the rest of the windshield remains freezing cold. The uneven expansion causes the glass to crack.
Ways to Defrost a Windshield and Avoid a Frozen Windscreen Altogether
1. Saltwater Solution
Saltwater can melt ice with a chemical reaction, dissolving the ice and keeping the water from refreezing. Mix water and salt in a spray bottle and shake or stir until the salt has fully dissolved. Spray the saltwater solution on your car’s windshield and windows. Be sure not to use too much of it and avoid it spraying over the other areas of your car. Once the ice starts to dissolve, use a brush, or your windshield wipers to wipe away the residue.
Using 3 spoons of salt in a litre of water is enough. Spray it or pour the water over the windshield covered with frost.
Note: Be sure to always scrape horizontally across the glass. Vertically chopping at the glass can cause it to chip and crack. Never use a shovel or knife to remove ice. It is also a good idea to keep an ice scraper in your car during winter months.
2. Park your car in the garage – Parking your car inside every night might seem like a lot of hassle when you have to back it out every morning, but it’ll save you from the pain of having to scrape the windscreen, too.
3. Cover your windshield with a tarp, towel, or sheet, and weigh it down to prevent ice from building up.