How Fog-X Works
First, we need to understand what fog is. What we call "fog" is actually tiny water droplets beading on the inside surface of you goggles. The tiny beads cause the incoming light to refract and reflect off the beading edges. With millions of beads throwing light rays all over the place, it's a miracle goggles work in the first place.
New goggles have a layer of anti-fog coated on the inside. It works... for a while. But it's very fragile and is easily rubbed off. Even if you don't touch it with your hands, just the repetitive beating of your eye lashes will take the coating right off.
Fog-X inserts have a similar anti-fog coating that is a hydrophilic layer that attracts water. That's right, it attracts water! The problem is not the water itself, it's the beading of water on your goggles surface. If you think about it, you can see straight to the end of a clean pool, right?
So, how does a hydrophilic surface prevent beading? It decreases the surface tension of the water droplets and lets the water come together to form a thin layer of water that you can see through clearly. No beading, means no edges, means no fog!