Last winter I spent 15 minutes scraping my windshield with a credit card because I could not find my ice scraper. My hands went numb. I was late for work. That afternoon I looked up every de-icing method I could find and tested them all.

The Spray That Actually Works

Mix 2 parts rubbing alcohol (70% isopropyl) with 1 part water in a spray bottle. Add a few drops of dish soap. Spray it on the icy windshield. The alcohol has a freezing point of -128°F, so it melts ice on contact. The dish soap leaves a thin film that slows refreezing. Keep the bottle in your house, not your car — it needs to stay above freezing to spray.

The Prevention Trick

The night before a freeze, spray your windshield with a mixture of 3 parts white vinegar to 1 part water. Wipe it mostly dry. The acetic acid in vinegar lowers the freezing point of water, so frost has a harder time forming. It is not 100% but it means you scrape for 2 minutes instead of 10.

What Not to Do

Do not pour hot water on a frozen windshield. The temperature difference can crack the glass — I have seen it happen. Do not use a metal scraper on side mirrors (they have a heating element that can break). And do not leave your wipers up overnight — a gust of wind can snap them back down and crack your windshield.