How does mask anti-fog work?

[ams511]

Ha ! Maybe we should try Rain-X. Works great on my truck, would hate to get it in the eyes though.

 

[Scubakevdm]

Another nice thing about baby shampoo is that in addition to being a good anti-fog, it also makes a great hair cleaning detergent for after the dive. I feel that it is worth noting that although spit may be substituded for baby shampoo as an anti-fogging agent, it should not be used as a hair cleaning detergent.

 

[H2Andy]

now you tell me...

 

[sgtmnstr]

I figure the reason a mask fogs up is that the inside of the lens is at a tempure below the dew point of the air inside the mask. So water
condenses on the inside of the lens. So how does de-fog (spit or
whatever) prevent this?

My first guess is that the stuff (spit, 500PSU, kelp juice....) afftects the water surface tension alowing the litle droplets to merge and form big droplets that roll of the lens, Or maybe it makes the lens less "sticky" so the condensed water rolls off.

I really don't even know why the condensed water on the inside of the lens stays in place Perhaps the antifog prevides a hydrophobic coating.

I could go on and propose many theories but maybe some one knows the answer.

Started using baby shampoo and water mixed in a spray bottle, about half and half. Works like a charm and only cost about 2 cents a gallon. Picked it up from my instructor, spray a little in your boots also, keeps em smelling baby fresh.................

 

[rcohn]

Started using baby shampoo and water mixed in a spray bottle, about half and half. Works like a charm and only cost about 2 cents a gallon. Picked it up from my instructor, spray a little in your boots also, keeps em smelling baby fresh.................

Why are you guys making the effort of mixing it with water and carrying a larger bottle? You have all the water you'll ever possibly want at the dive site. Just put some baby shampoo in a small bottle, squeeze a few drops in the mask, add a little water when you rub it arund and rinse it out and you're all set.

Ralph

 

[H2Andy]

brilliant

 

[SamDiver14]

I love engineers.

 

[Laurence Stein DDS]

I hope I don't upset all those that replied...Defogs, either detergents, toothpastes, soaps, alcohols, or glycerine work not because they clean the mask (although they do clean the surface as well) but because, as a surfactant, they decrease surface tension. Drops or microdrops of water do not mound up as beads but, instead lay "flat" and their margins intersect forming a single sheet of water.

The surface of the glass in your mask may appear smooth and shiny but, in fact, it is pitted with microscopic depressions. Moisture is attracted to this uneven surface. Decreasing the surface tension and creating a moisture film prevents fogging.

Toothpaste is recommended for new silicone masks because microscopic particles of silicone...which repels water is impregnated onto the glass. The mild abrasive of the paste simply rubs away the silicone particulates. Toothpaste also has "foaming agents"...a long name for something a surfactant does. Therefore toothpaste can also be used as a defog in addition to its use as a glass cleaner.

Glycerine in actually a tri-alcohol. Alcohols mix with water and decrease surface tension. That is why you rinse your ears with alcohol...it breaks the surface tension of the water in your ear and allows it to be rinsed out. In addition, water goes into solution in alcohol forming an azeotrope. When you dump out the alcohol, you are also dumping dissolved water. This is also the reason that alcohol is used in fuel to remove moisture...the water dissolves in the alcohol and the mixture is then combusted and removed in the exhaust.

In addition, glycerine is not a biproduct of soap manufacture. Rather, it is instead capable of being turned into a soap. Neutrogena is glycerine soap.

Edit: Yikes...I made a mistake! Glycerine is a byproduct of soap manufactured from animal fat (tallow) and is capable of being saponified (turned to soap). Hey, I just want the facts!...Larry

So any compound capable of decreasing surface tension should be able to "defog" a mask.

Hope this makes sense. Everyone was sort of in the right track and with any luck I haven't made too big an ass of myself!

May your defog last as long as your dive.

 

[beachdivequeenbelam]

I hope I don't upset all those that replied...Defogs, either detergents, toothpastes, soaps, alcohols, or glycerine work not because they clean the mask (although they do clean the surface as well) but because, as a surfactant, they decrease surface tension. Drops or microdrops of water do not mound up as beads but, instead lay "flat" and their margins intersect forming a single sheet of water.

The surface of the glass in your mask may appear smooth and shiny but, in fact, it is pitted with microscopic depressions. Moisture is attracted to this uneven surface. Decreasing the surface tension and creating a moisture film prevents fogging.

Toothpaste is recommended for new silicone masks because microscopic particles of silicone...which repels water is impregnated onto the glass. The mild abrasive of the paste simply rubs away the silicone particulates. Toothpaste also has "foaming agents"...a long name for something a surfactant does. Therefore toothpaste can also be used as a defog in addition to its use as a glass cleaner.

Glycerine in actually a tri-alcohol. Alcohols mix with water and decrease surface tension. That is why you rinse your ears with alcohol...it breaks the surface tension of the water in your ear and allows it to be rinsed out. In addition, water goes into solution in alcohol forming an azeotrope. When you dump out the alcohol, you are also dumping dissolved water. This is also the reason that alcohol is used in fuel to remove moisture...the water dissolves in the alcohol and the mixture is then combusted and removed in the exhaust.

In addition, glycerine is not a biproduct of soap manufacture. Rather, it is instead capable of being turned into a soap. Neutrogena is glycerine soap.

So any compound capable of decreasing surface tension should be able to "defog" a mask.

Hope this makes sense. Everyone was sort of in the right track and with any luck I haven't made too big an ass of myself!

May your defog last as long as your dive.

THank you for your info. I like this kind of answer. It tells me exactly what I need to know and why. I am a WHY? person. I always want to know Why?

 

[Wijbrandus]

I used rain-x on my mask. It works really well on the outside (no water beads when I get back on the boat!) and keeps the fog down on the inside. I think everyone should try it. And the bottles are bigger than your usual defog, so you don't lose them easy, and you can still use it on your car. Awesome stuff.

I'm kidding of course. The stuff is great for the car, but I don't think it'll do the trick on my mask. Though it might do the trick on the skirt, as in destruction...