There was a thread just below that was like 5 pages long about mask fogging.. and I was just reading through it yesterday.. So you asked a good question at a good timing!
Here's the thing. Usually my mask does okay in the ocean, but I went to my first pool class as part of the divemaster training, and my mask fogged like crazy. (my OW training was all in the sea) So, I checked a few things out.
First of all, the silicone on a new mask is not easy to remove. Tooth paste it like 5 times, the glass and the silicone parts. I brushed it with an old toothbrush just to make it easier. 5 times with fingers is going to be tiring.
The consensus on how to apply defog seems to be:
1. apply to dry mask
1.5 you can dry the defog before rinsing, but didn't seem to make much of a difference
2. rinse just before use
3. don't touch the defog when rinsing. Swirl the water around by moving the mask.
4. Once you've rinsed, use it. If it dries after rinsing, wet it again before using. Or you can do a mask clear once you get in the water.
After I've done all these steps, I could blow nose air straight into the mask for several minutes and still not get fog. (experimented on dry land tho) The only reason I quit the nose blowing experiment was because I didn't want to roam around the house with a mask on my face. Just as a reference, without defog, the mask fogged up on the second nose blow, 5 seconds into the experiment.
And why it didn't work in the pool was, I rinsed with pool water, and that seemed to have washed the defog off. Rinse with fresh water if at pool.
Anyway, the rule of thumb is, it always has to be glass, a layer of pure defog, a layer of defog mixed with water, and then air. I think. I'm wondering about the "layer of pure defog" which translates to step 1.5, letting the defog dry before rinsing.. it probably helps make the defog last longer because letting it dry creates a denser layer of defog compared to rinsing right after applying.
I was also wondering about applying dry when not diving, and do the "buff untill dry" thing. In theory, it'll create a thin layer of defog that dries up and sticks to the glass, and each time you apply defog on the boat, you'll always have a thin layer of pure/although very dry defog come first, and then the defog you apply.. so ideally, it'll work like a saftguard shield.. But that's just my guess. Anyone know?
