Spit or ....

[kirkryan]

I am looking for your thoughts on keeping your mask fog free. Spit has always worked for me so it's not a problem of mine, but I never actually understood why it works. I guess there is something in spit that keeps water molecules from condensing at the lens/air interface but what is it? Anyone have any ideas? Oh, and any defog purchasers, feel free to explain the chemistry behind the bottled stuff too. I have yet to find any that actually works longer than it takes to rinse your mask but if you have, please tell us about it.

 

[ianw2]

Your spit has proteins and all sorts of large molecules in it. They adhere to the glass on the inside of your mask and prevent water vapor from condensing on the glass.

Commercially available anti-fogs use surfactant chemistry, too. The idea is to coat the glass with a very thin film of large chin molecules that work just like your spit. The surfactants also make water "wetter". That means that instead of forming beads of water on the inside of the glass and fogging everything up, the water vapor forms a film.

Anything that keeps water vapor from settling on the glass or makes the water too wet to form beads will work as an anti-fog.

As the old Monsanto motto says, "Better living through chemistry!"

 

[GrandpaScuba]

I have tons of commercial defog, but I usually forget to use it until I'm already chest-deep in water. So, I actually use spit more often. Spit works fine, and unlike some commercial preps, it will never burn your eyes (unless, perhaps, you chew!) However, I always clean my masks very well after each diving day. This helps prevent a build-up of nasty organic material.

 

[fishoutawater]

I've never tried any of the bottled concoctions, but I always theorized that whatever I use, it has to be slimy. I don't know why slimy stuff works other than fog itself is just microscopic droplets of water and each droplet has its own surface tension and can stick to glass, but when you cover the surface with something slimy, the droplets can't hold their surface tension, and they run into each other forming bigger droplets till they roll down your faceplate. But with plain glass without something slimy coating it, the microscopic droplets can stand alone and not run into each other.
Make sense?

Aw, ya'll beat me to it.

 

[Wildcard]

If your defog isn't working your using it wrong. The most common problem is over rinsing. One quick rinse, put your mask on and leave it on and you should be good to go with spit or commercial defog.

 

[Dave Zimmerly]

Baby shampoo is the shiznit.

Dave (aka "Squirt")

 

[FunkyDiver]

toothpaste by Colgate. the Sponge Bob brand. No kidding! It's a blue gel. It works very well.

 

[vablackwater]

Baby shampoo is the shiznit.

Dave (aka "Squirt")

^^ what he said

 

[Knight1989]

I'm a cheap skate, I always use spit.

 

[EvilSlumLord]

Yup, Baby shampoo works great. My OW instructor pointed to a bottle of the stuff during our first pool dive and said something about it being the best defog available (and cheap too). I bought one of those large bottles and use a small dispenser bottle in my dive bag. I suspect I may have to buy one more for my entire life at this rate. Hasn't failed me yet (and I definitely had fogging before trying it).

Spit seems to work (every person on the dive boats in Tahiti seemed to use that method) so it all depends on what you prefer. I wouldn't buy the stuff from the dive shop given how expensive it is and that there are definitely other alternatives that work well.