I used to pour hot water on my windshield. Let me save you the repair bill: do not do that. The thermal shock cracked a six-inch line across the glass on a 12-degree morning in February. Four hundred dollars and a very cold drive to the auto glass shop later, I decided to learn the right way.

The spray that melts everything

Mix two parts rubbing alcohol to one part water in a spray bottle. Add a few drops of dish soap. Spray it on the icy windshield and wait about 30 seconds. The alcohol has a freezing point of -128°F, so it melts ice on contact without refreezing. You can wipe it away with your wipers or a plastic scraper — it will already be slush by then.

I keep a bottle of this mix in my car all winter. It costs about 50 cents per batch and works faster than any commercial de-icer I have tried.

The overnight prevention

Spray plain white vinegar on your windshield the night before a freeze. Vinegar lowers the freezing point of water, so frost forms more slowly and is thinner in the morning. It does not prevent ice entirely in a hard freeze — below about 20°F it loses effectiveness — but it makes scraping about 50% easier.

You can also cover your windshield with a towel or a piece of cardboard held down by the wipers overnight. Pull it off in the morning and the glass underneath is clear. This is the old-school Midwestern method and it costs zero dollars.

Start the car right

Crank the defroster on full heat but do not blast the fan speed right away. The engine needs to warm up first — blowing cold air on ice does nothing. Turn the temperature to hot, set the fan to low, and direct it at the windshield. As the engine warms, the air gets hot, and the ice releases from the glass in sheets. After about five minutes, you can crank the fan and the remaining ice will slide right off.

Plus: turn on the rear defroster and heated mirrors if you have them. And for the love of your paint, never use a metal scraper — plastic only, and scrape in one direction, not back and forth like you are sawing wood.

I have not cracked a windshield since that February. The spray bottle lives in my trunk year-round.