There’s never a good time for your lenses to fog up. But for anyone who’s experienced a fair amount of cold weather or has a passion for winter sports, fogging lenses is likely a familiar occurrence. The good news is, you don’t have to keep living with it--understanding the basic science behind fogging on eyewear lenses is how we know what works (and what doesn’t) to prevent it from happening. Ready to put foggy lenses behind you? Read on...

The science of why it happens

Fogging is nothing more than condensation of water vapor on the surface of your lenses. That’s right: the same phenomenon that causes ‘sweat’ to appear on a cold glass of iced tea on a hot summer day is also responsible for your lenses clouding over. Whether outdoors or inside, when water vapor in the air contacts a surface cold enough to change to liquid phase, the liquid droplets will “stick” to the surface if sufficient adhesive interactions take place with the water molecules. To reverse fogging, the surface must warm up sufficiently to promote evaporation. Our best course of action, then, would be to make it harder for condensation to stick to the lenses of your glasses. How? Let’s look at the options…