Why Does my Mask Fog Up and How do I Prevent This?
An otherwise great time diving or snorkeling, while not quite ruined, can certainly be dampened a bit by mask fog blocking your view, impeding communication and needing frequent rinsing out or mask clearing. Tilting your head at funny angles to try and see what your guide is pointing out is not the most fun way to spend your time underwater! All masks will fog up if not treated correctly, but any foggy mask can be fixed by creating a super smooth surface that water cannot hang on to.
Fogging is caused by condensation which happens when the temperature of the glass lenses is lower than the air inside the mask.
All air has water vapour, which is just water in the form of a gas. The humid weather we get here in the tropics is caused by lots of this water vapour, which is what we then introduce as the air in our scuba masks.
The lenses on your mask are in contact with the water outside, which even at a very comfortable 28 – 30 degrees celsius, is quite cool compared to the air inside next to your face. When the water vapour molecules hit the cool mask lens, they cool down and turn back into liquid water.
While your mask looks clear and smooth, it is actually full of microscopic imperfections in the glass, not to mention dirt specks, dust and oils. The moisture forming inside uses these to attach on to and blocks your view as mask fog.
So to prevent mask fog we need to introduce some kind of slick substance to coat the lens. This layer will then become too smooth for the condensed vapour to cling or grip on to, and so the moisture will just slide down the mask surface instead.
The typical cures, whether anti-fog, spit, shampoo, dish soap, etc. are all pretty slippery liquids. We gently rub one of these on lens and rinse off in water just before putting on the mask. You do need to be super careful with rinsing: if you rinse too much or too aggressively, the coating will come right back off.
Once the mask is on with a good seal, try to keep from removing it which just allows more humid air and therefore moisture to enter.
Our professional and friendly PADI guides will help with your equipment and remind you how to prepare your masks before you enter the water to snorkel or scuba, so you can enjoy a clear view of the incredible corals and schools of tropical fish around Koh Phi Phi.
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We look forward to diving with you in Koh Phi Phi soon!