Why do swimming goggles fog up?

July 28, 2009

The summer is upon us, and that means plenty of snorkeling, scuba diving, and swimming. If you do any of these things, you've probably run into a familiar problem — your goggles fog up as soon as you put them on! So, what causes this fogging up, and what can you do about it?

First of all, the reason your goggles fog up is the same reason that your car windows fog up in the winter, or why your bathroom mirror fogs up after a hot shower. Warm water vapour comes into contact with a cold surface and condenses back into the liquid phase, depositing as a thin film on the surface. In the case of the goggles, the warm air comes from the heat of your skin around your eyes, and the air or water surrounding the goggles is usually a lot cooler.

Did You Know?
Goggles fog up when water vapour, warmed by your skin, condenses on the cold lenses.

Next, how can you prevent your goggles from fogging up? There are a few ways — some quick and easy, and others that you'll have to pay a bit for. The simplest, most tried-and-true thing to do is actually to lick or spit into your goggles before you put them on! (Just try not to gross out anyone nearby TOO much!) If you rub the saliva around the lenses, it will leave a thin layer of water on the goggles that will protect it from fogging up temporarily. Another thing to try (before the spitting!) is to submerge the goggles in water for a short time. This will lower their temperature to be more in line with the air and water around, and will improve the fogging problem a bit.

Did You Know?
The easiest way to prevent fogging is to spit into them!

Now, I can hear you saying "I can't imagine Michael Phelps spits into his goggles before a race!" You're probably right about that! If you are willing to spend a little money, you can get products you can spray on the goggles to prevent fogging. However, you have to be careful that you have a good seal when you put them on, because if the spray mixes with water and gets into your eyes it can hurt! And finally, an even more expensive option, but the one preferred by avid divers and professional swimmers, is to get a top-end pair of goggles. Nowadays, most such goggles utilize technology that almost eliminates the problem of fogging.

Did You Know?
Fog-free goggles do exist — juts be prepared to pay a bit more for them!

Unfortunately, the fog-free coating on these goggles tends to wear out over time, so you will have to buy more. But hopefully some of these tips will reduce frustration and increase fun around the water this summer!

Learn More!

How to prevent swimming googles from fogging up

Why does spitting in goggles prevent them from fogging up?

Top 10 goggles

Derek van Pel

I am working on a Ph.D in Molecular Biology at the University of British Columbia, where my research is aimed at finding new anti-cancer therapeutics that can target weaknesses specific to tumour cells. I am an avid science educator, and when I'm not in the lab, writing for CurioCity, or volunteering with Let's Talk Science, I can be found teaching a 3rd year undergraduate biochemistry lab!



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