How Can You De-Ice Your Windshield?

Use Chemistry To Clear Ice off the Windshield

Don't drive like this! You can use common household chemicals to de-ice a frozen windshield.
Martin Diebel/Getty Images

Do you have tips and tricks for removing ice from your car's windshield or preventing it from forming in the first place? I was asked if science can be applied to defrost a car windshield more quickly than waiting for the car's defroster to warm up and melt the ice. Here are a few different ways you can defrost your windshield quickly.

Simple Tips To Deice a Windshield

Warm water works if it's not super-cold outside.

You can pour warm water over your windshield and use the wipers to clear it off. If it's really cold outside, all you are going to accomplish is adding a thick layer of ice to your windshield (best case) or cracking your windshield from the temperature difference (worst case).

Saltwater works for the same reason salt works as a de-icing agent (and warm saltwater would be your best bet). The ions in the salt lower the freezing point of water, so a little ice will be melted by the saltwater. This water will attempt to re-freeze, but the temperature will need to be colder than 32°F for that to occur. All salts aren't created equal for de-icing. Normal table salt works when it isn't really cold. Road salt, which has a different chemical composition, works better when the temperature is very low. Salt exposure isn't great for your car, so keep that in mind. Actually, any chemical that you add to water acts as an impurity and lowers the freezing point of water, so wiper fluid would melt the ice more quickly than pure water, too.

A quicker way to melt the ice on your windshield is you already know... placing your bare hand against the windshield. This works because (a) your hand is warm and (b) your hand is solid. Warm solids contain more particles per unit area to convey heat to the windshield than you would get from warm air (molecules in the air are very far apart).

So, any warm solid will de-ice the windshield better than air. Any warm liquid will de-ice better than air for the same reason (ice melts faster in water than in does in the air of the same temperature).

You don't have to use your hand. The base of a warm shoe would work; so would a warm book. The denser the object is, the more effective it will be. Therefore, you'll get more de-icing power from your shoe than you would from.. say... your sock. The heat capacity of the material matters too, which is part of why your hand is such a great defrosting tool.

If it's not too cold, I'd probably go with a warm, damp towel on the windshield. If it's bitterly cold, the ice scraper is still your best bet. If you have a garage and live in a warm climate, you can prevent the frost from forming in the first place by parking inside.

You can also use common household chemicals to defrost your windshield. These materials apply freezing point depression to clear the ice. It's a good idea to use your wipers and fluid after you apply them because they can be sticky or corrosive. Of the list, rubbing alcohol is your best bet for speeding defrosting without damage:

  • pickle juice (saltwater brine)
  • beet juice
  • Kool-Aid (or other sugary soft drink)
  • soda (with sugar)
  • vinegar
  • rubbing alcohol