Perhaps you've seen the above video, or similar, going around. It's one of the hottest car-care tips on the internet right now: use shaving cream to fog-proof your windshield.
It's a great tip because it really works. Who knew all that shaving cream you've been wasting on your hair could have been spent keeping your visibility clear on a rainy day.
How does it work though?
If you've ever been snorkeling, you've probably spritzed a solution of baby shampoo in your diving mask to keep it from fogging up underwater. The shaving cream works the same way. Both contain detergents which lower the surface tension of water.
Surface tension is why you had to measure from the meniscus in science class, it's why water-bugs can walk on water, and it's why raindrops form.
Fog, though it looks like one solid opaque sheet, is made up of thousands of tiny water droplets which scatter light every which way, and give the glass a frosted effect.
The residue shaving cream leaves behind lowers surface tension so these droplets cannot form. The water clings to the glass flat, and does not scatter light. The same amount of condensation is still forming on the glass, but light passes through it as directly as the glass itself.
While some aspects of car maintenance are as simple as spraying on shaving cream, some are better handled by trained professionals. If it's time for an oil change, tire rotation, or inspection, make a service appointment with Pellegrino Auto Sales in Batavia, NY.