That´s it, I was wondering that while I was snorkeling in Koh Mak last weekend. I learned the trick from some epysode of Cousteau´s Underwater World (or whatever it was called) many years ago, and I´ve been using it ever since; but I don´t know how it works.
Any ideas?
Saliva contains surfactants (wetting agents) that coat the glass and prevent the “fog” from remaining microscopic droplets. Saliva does contain surfactants, but the contention that these are the causitive agents in this process is just my WAG.
I’ve been doing it for 20 years. I remember my Cert. Dive in Murkey water Newport Rhode Island. I was standing next to a guy waiste deep in the water both getting ready to go under. I spit in my mask rubed it around and put it on…He had this $5 a bottle stuff to spritz on the lense…He squirted it out, and I laughed as I went under… thinking: $1500 dacor outfit, $100 mask, $100 diving certification: spitting on your mask…priceless 
It occurs to me that if you coat the lens with saliva, it has a clear wet coating as you dive. Add a bit of condensed moisture, it just combines with the wet coating, rather than forming new, opaque, droplets like it would on a dry surface.
The existance of surfactants may play a big role in creating a coating that will absorb added moisture.
Soap works as well, but I wouldn’t want to get it in my eyes. It’s more then just the wetness.
My diving instructor told me that it was crap. He said it doesn’t work better than any other clear, viscous, hydrophilic liquid, and that it works much worse than most. He spent 20+ years in the Navy, so I believe him. The BEST, he said, was water-based, gel lubricant. And yes, he meant that kind of lubricant.
hmm…
Had a lot of that on hand in the Navy, did he? 
For what it’s worth, I’ve never found saliva to be of any use at all in cold New England waters. I haven’t found anything that works.
Indeed. Spitting in a mask that has already had water in it doesn’t seem to do diddly - in that scenario you just get a mixture of droplets of water and fogged glass that combines to give 100% crappy vision. You need to apply your goop of choice to dry glass and smear it about properly, then rinse with water. Then you get a nice thin film of water over the glass which absorbs any condensation, as described. I’m not up on the exact mechanics of it, but as democtritus says, anything hydrophilic which sticks to the glass and lets you see through it should do the trick. I’m 100% sure that there are better-performing products than spit, but for warm-water diving spit is plenty good enough, particularly if you eat a lot of dairy. Yoghurt and cheese with breakfast will set you up for your day of diving.
Sal Ammoniac - probably a dumb question, but have you done the toothpaste trick to get any silicon off the glass? People go ice-diving in the arctic and so on, so it must be possible to prevent fogging in New England.
If you read my post up thread I spoek about diving in Newport, Rhode Island. I spit on my mask everytime I go under up here in New England. Granted I only dive from June through September, but it’s still damn cold in June. I was at Ft.Wetheral, Jamestown, RI not too long ago and my mask lasted 30 minutes with no fog. There you have it.
it may be because of the lasic and blood pressure meds i take, but my spit is worthless even in the bahamas, where the water is about 85 degrees. the dive master and i just use a cheap mix of liquid detergent and water. he knows the mixture proportions - i don’t - but it works just fine.
This is one reason why I love my AGA. It never fogs.
You are likely to get condensation, or fog, inside your mask no matter what you do. Spit or commercial anti-fogs work in the same way. They lower the contact angle of the water droplets, essentially causing the water to sheet. They don’t actually prevent condensation.
Surfactants certainly increase wet-out, but they are normally defined as molecules with a hydrophobic tail and hydrophilic head. I don’t know that spit increases wet-out by this exact mechanism.
Spit does not work as well as simple baby shampoo (which I know contains traditional surfactants) which in turn doesn’t work quite as well or as long as the commercial anti-fogs.
Nothing is going to work very well if your mask isn’t clean. So clean it if you aren’t sure.
All very informative people, thanks.
Aha… next Monday I´m going without my GF to Koh Kood, I´ll give you her e-mail so you can explain to her why I´m packing the gel!
