String and DevonDiver covered the defogging procedures very well so I'll skip that. What I will add is that even if you do spit in your mask (I'm covering spitting because it is the only defogging solution I have ever used or had contact with) you won't be guaranteed to be fog free. You have to really wipe it all around, not just spit then rinse.
I had a student whose mask fogged up repeatedly after I personally toothpasted it for about 15 minutes. Then her mask leaked so we switched and then, on the next dive, the mask she was wearing (my mask) fogged up! This was despite my mask never having a history of fogging up for 150 dives. So next time she she defogged her mask (actually my mask) I watched her and she wasn't rubbing it in properly. So naturally her (my) mask also fogged up.
So I guess what I am trying to say with this long winded and convoluted story is that you should make sure you defog your mask properly before the dive even if you have already pretreated the glass with a lighter or toothpaste.
I had a student whose mask fogged up repeatedly after I personally toothpasted it for about 15 minutes. Then her mask leaked so we switched and then, on the next dive, the mask she was wearing (my mask) fogged up! This was despite my mask never having a history of fogging up for 150 dives. So next time she she defogged her mask (actually my mask) I watched her and she wasn't rubbing it in properly. So naturally her (my) mask also fogged up.
So I guess what I am trying to say with this long winded and convoluted story is that you should make sure you defog your mask properly before the dive even if you have already pretreated the glass with a lighter or toothpaste.
