There you are, about to check “swimming with humpback whales” off the bucket list. The excitement builds as the animals approach the boat, you hit the water… and your mask immediately fogs up.

What can you do? If you’re comfortable with basic diving skills, you can flood a bit of water into the mask, let it wash across the glass, then clear it with an exhale through the nose. But that’s only a temporary solution.

Fog prevention begins before you enter the water. In the old movies, the scuba diving “frogmen” just spit into their masks and left it at that. But in reality, there are better solutions than saliva.

The Science of Mask Fogging

Before we get to that, we should pause for a short science lesson.

Even when your mask fits perfectly over your face, and there is no chance of a leak, there’s still water in your mask. It’s suspended within the trapped air space in the form of water vapor. And as we know from watching a frosty bottle of beer on a hot day, when air contacts a cool surface, suspended water vapor comes out of the air and condenses into droplets on the beer bottle.

The same thing happens when the moist air inside your mask hits the face plate, which is cooled by the water on the other side of the glass.

If the glass were perfectly smooth, the condensation might form as a perfectly smooth sheet that you could see through clearly. But even though the face plate may seem smooth to you, the surface is actually riddled with microscopic imperfections, small specs of dirt and residual chemicals from the manufacturing process. These uneven surfaces create points that collect water vapor, and cause the vapor to coalesce into small droplets rather than a smooth sheet. Hence fogging.

mask defogging tips

No fog, no worries. (Flickr Creative Commons / Ilse Reijs and Jan-Noud Hutten)

How Can You Prevent Mask Fogging?

To stop the fogging, you need to make the faceplate as smooth as possible. This begins with cleaning. Any mask will benefit from a good lens cleaning, even those right out of the box. Brand-new masks often contain residual coatings from the manufacturing process, and the silicon materials will off gas during packaging, leaving a film on the lens that should be removed.

Here are a few good ways to prevent mask fogging.

Add a dollop of toothpaste. Avoid the gels, because they don’t have sufficient abrasive properties. Instead, use the good old white stuff—add a few drops of water and polish gently but thoroughly with a soft cloth. It’s best not to use your fingers, because they can leave residual oils on the lens. Check the mask’s specs before you start cleaning, because some new masks have polycarbonate lenses rather than glass. Toothpaste is a no-no for these relatively softer materials, because it can scour the surface, creating tiny grooves that actually increase the lens’s susceptibility to fogging. Instead, go for a mild soap solution and a soft microfiber polishing cloth.

Apply a thin layer of an anti-fogging solution. A clean mask is less susceptible to fogging, but not immune. Even when clean, a glass or polycarbonate lens will still have small imperfections or imperceptible scratches in the lens surface that may promote fogging. Adding this extra layer will create a slick, viscous bind that transforms the condensation into a smooth, thin film of water. Some commercial defog solutions are readily available, and you can also make your own by mixing water and baby shampoo in equal amounts.

For best results, you’ll want to apply defog to a clean, dry mask lens, using just enough of the defog to create a uniform covering. Thicker solutions may require a bit of spreading, while solutions such as the baby shampoo/water mix can be swished around. More is not necessarily better, because you don’t want the stuff dripping into your eyes. If there’s more than a thin, even coat, you might want to give the mask a quick swish in fresh water shortly before entering the water. Just make sure you don’t wash off all the coating, and then don’t touch the mask again until you are ready to put it on.

Have a question about masks or anything else related to snorkeling and diving? Drop us a line at Caradonna Adventures. We’ve been sending divers and snorkelers to dream destinations around the globe for almost 40 years, and we would love to help you discover the amazing sights of the underwater world.

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