DIR guys are trained to dive blind anyway so who cares it if fogs lol!
---------- Post added November 23rd, 2012 at 11:43 AM ----------
Originally Posted by
SeahorseDeb 
[/QUOTE]Belmont, Why does spit work for some of us and not for others? I've been spitting in my masks over the years, different manufacturers too, and no difference....I just don't have fog issues. I quit diving for a few years and when I came back and heard about "anti-fog" I just couldn't believe it! So, I'm still looking for some theory here to explain the preponderance of this thread that most posters cannot rely on their spit.
I am in no way being critical, I'm just wondering if there is some biology behind this, and no, I will not sell my spit![/QUOTE]
I'm no scientist but here are some of my thoughts on the subject, surely some are way off, but here goes.
I think it involves physics and chemistry.
Surface tension that prevent water molecules from sticking together. like oil droplets on water, is the cause of the problem.
If the glass surface is covered with contaminants very tiny water droplets aggregate on each particle and form a sphere that acts as a lens diffracting light rays. The effect is like looking trough a frosted or fogged up window.
When we use spit, the enzymes that are present in it and serve in the beginning of the digestive process by breaking down the bonds in the food molecules, keep the water droplets from forming thus creating a smooth surface.
A very thin film of water molecules, all joined together, letting light trough like a regular window pane.
Any surfactant like spit, shampoo, detergent will give similar results.
Spit is easily available but varies in it's composition, it probably has more digestive enzymes in it if one is close to meal time or hungry and less when spit has to serve to simply keep mouth tissues hydrated, personal variations certainly exist.
Baby shampoo should be preferred because it's a good surfactant and will not irritate eyes, I've had a dive scrapped because of detergent in my mask, some of it went in my eyes. It's also way less expensive that the stuff sold to divers.
Also the less surface contaminant, like skin oils and release agents used in the manufacturing process, there is on the glass surface to attract those pesky water droplets the less chance there will be for fog formation.
Cleaning methods vary greatly but should involve a strong detergent or mild alkali with some mechanical abrasion like the one offered by tooth paste, oh...also patience and elbow grease.
Cheers
). A properly cleaned mask is the basic requirement.
