Foggy masks are a common frustration among fans of watersports. Believe it or not, there really are some defogging methods that work reliably.

Why Do Lenses Fog?

Most people know that their mask fogging up is caused by condensation, but they may not realize than effective defogger doesn’t actually stop condensation. Because of the differences in temperature and moisture between the inside and outside of your mask, it’s simply not possible to prevent condensation. The goal of defogging is not to stop condensation — it’s to prevent the microdroplets of moisture from clinging to the lens in a fine, misty sheet. This is accomplished with surfactants — substances that lower surface tension between the droplets and the lens. The result? The droplets slide down and off the lens as quickly as they form.

Defogging Won’t Last Forever

Some dive masks are treated with a defogger before they leave the factory, but it’s important to know that defogging treatments are always temporary. Liquid, gel and sheet-type defogging treatments will all lose their effectiveness over time, so they must be reapplied.

Pro Tip: Start With a Clean Lens

Whatever method you use to defog your lenses, it’s crucial to begin by making sure they’re clean and dry. Mineral deposits from the sand, body oil, sweat, dust and other impurities prevent defogging treatments from totally adhering to the lens. Even brand new masks and goggles often arrive with traces of lubricants and adhesives that were used in the manufacturing process and will interfere with defogging.

Before applying any defog treatment, wash your mask lenses thoroughly with a gentle soap that doesn’t have any added moisturizers or conditioners that could leave behind a film. Baby shampoo or basic liquid hand soap are both great options for this purpose. After gently scrubbing the lenses with the soap, rinse them with clean, fresh (not salt) water.

Pro Tip: Defogger Won’t Adhere to Wet Spots

If you’ve got a mask or pair of goggles with a couple of stubborn spots that always seem to fog up even when the rest of the lens is clear, it’s probably because these spots still had moisture on them when you applied your defogger. Drying everything completely is key to a successful defog treatment that lasts. If you’re using a cloth to dry the lenses, make sure it’s microfiber or chamois so that it doesn’t leave lint behind.

Defog Options: From Spit to Film

Whichever methods you choose, it’s critical that you don’t touch the lenses once you’ve applied the defogger and rinsed the lenses. Body oils from your fingers will interfere with the surfactant’s effect. It’s also important not to rest your mask on your head between uses — this can transfer oils or hair products to the lenses. Finally, avoid leaving your treated mask or goggles in direct sunlight between uses; the heat can break down the defogging treatment.

1. You’ve probably seen other divers spit onto their lenses, rub the spit around and then rinse them in the nearest water, whether it’s saltwater or freshwater. This method does work, but the treatment won’t last very long — generally only one dive.
2. Commercial Defogger. A commercial defog liquid is essentially a chemically engineered surfactant, so you know it will be effective. One of the advantages of using a defog liquid is that it’s easy to get full, even coverage. The Seavenger Lens Cleaner and Anti-Fog comes in an easy-squeeze tube with a tried-and-true formula that works like a charm. Commercial defoggers like these can last through multiple dives, provided that you rinse the mask gently in freshwater after each use and avoid touching the lenses.
3. Commercial Defogger Film. Most of us are familiar with screen protectors on our phones and tablets. Well, defogger films for dive masks work the same way: a clear layer of specially-engineered film is applied directly to the clean, dry lens. These films can keep lenses clear for multiple dives, but they create more waste in the environment and they can start to peel off if you touch the lens too often.