Why does my dive mask fog up?

Fogging masks have been a persistent issue for scuba divers since the inception of the sport. While we teach partial mask clearing in the PADI Open Water course to handle fogging by adding some water and clearing it out, a perpetually foggy mask can still ruin a dive. In this guide, we’ll explore why scuba masks fog up and offer tips to prevent it.

The basic principle behind mask fogging is simple: when the temperature inside the mask is greater than the outside, condensation from the air inside forms. This temperature difference occurs because our body temperature (around 37 degrees Celsius or 98 degrees Fahrenheit) is higher than the surrounding water temperature. The condensation is further aided by our damp breath or sweat and settles on the mask’s glass. This is typically because of silicone residue left over from the manufacturing process, dirt, or oils on the inside glass, which can all help the process. Therefore, the first step to reducing fogging is to ensure your mask is perfectly clean.

Here are some tips to avoid having a foggy mask:

Change some habits

Focus on Breathing Technique: Avoid breathing out of your nose, as warm, moist air from your body can cause condensation. While it may be challenging for beginners, practice breathing solely through your mouth while diving. This adjustment can significantly reduce fogging issues.

Use a Well-Fitting Mask: A correctly fitting mask is crucial, especially for individuals with different facial structures. Many universal masks are designed for larger Western noses, but those with smaller noses might find that air escapes into the mask, causing fogging. Brands like Gull and Cressi offer masks designed for smaller faces. Additionally, a poorly fitting mask can let in excess water, contributing to condensation.

Handle with Care: Avoid touching the inside of your mask, especially after applying a defogger, as oils from your fingers can negate its effects. Instead of using your fingers to apply defog, opt for a product that can be swished around inside the mask and then rinsed without manual spreading.

General Care of your mask and good habits

Regular maintenance of your mask is also vital. Cleaning your mask with toothpaste can reduce fog, as new masks often accumulate residue over time. Saltwater, grime, and pool chlorine can cause unwanted buildup, so clean your mask regularly using a soft-bristled toothbrush and avoid touching it with your fingers.

Before diving, try to put on your mask with a dry face, using a towel to remove moisture if necessary. Once your mask is on, try not to remove it to keep water out. After each dive, rinse your mask with lukewarm or cool water and pat it dry with a clean towel. Occasionally wash it with mild soap to prevent dirt or oils from building up on the lens. Never store your mask while it is wet, as this helps prolong its lifespan.

Mask Defogging Methods

Additionally, there are several ways to keep your mask clear of fog, note that often with products like these you want to leave a thin film inside the glass after application and a very gentle rinse. If you end up rinsing all the product (or human spit) off then it will no longer be effective in minimising fog.

• Use Defog Products: Many brands offer sprays and serums designed to prevent fogging in snorkel and scuba masks. Always follow the directions—some require rinsing, while others need to dry on the lens. These products are generally inexpensive and long-lasting.
• Try Baby Shampoo: A popular and cost-effective alternative to defoggers, baby shampoo can be diluted in water and sprayed inside the mask. It is gentle on the eyes and biodegradable, making it a safe choice.
• Use Human Spit (the ‘hawk tuah’ method): The traditional method of using saliva can be surprisingly effective. Although its popularity may have decreased due to COVID-19 concerns, many divers still swear by it. Simply apply saliva to the lens, light rinse, and wear your mask.

By following these tips and maintaining your equipment, you can enjoy a clear view of the underwater world on your dives.