Why is spit a good mask defogger?

Let’s start with the basics…

General idea: spit, rub, spread, rinse, wear mask.

1. Why do scuba masks fog up underwater?
The seawater surrounding the outside of the mask gives a cool surface for condensation to take place. Also, the microscopic potholes on the lens give a very good grip hold for water droplets to settle. So if you’re a nose exhaler, the vapour from your nose will condense on the cooler surface of the glass which will result in an annoying congregation of water droplets. This will then lead to numerous mask clearing practices. Your instructor will be very pleased…

2. So if water is relatively transparent, why can’t we see through the mist?
Depending on the size of the droplets, they form an irregular surface which ends up distorting the light that passes through the mask, hence causing it to be difficult to see thru.

3. So why does spit work?
Some have said that the enzymes in our saliva work miracles. Or, some have said that because saliva in its own nature has moisturising components. Well, the truth is… it is all true! Mostly that is.

First, think about what saliva is actually there for; moisturising, enzymatic digestion, decay fighter, lubricant, solvent for tastes etc…  Now, think of someone who had his salivary glands yanked out by a sadistic roman soldier for example. The environment in our mouths, as we were designed to be, is a relatively waterproof surface due to a number of water repelling fat like substances (lipids) in the lining cells. Unfortunately, these lipids give excellent conditions for water droplets to form (imagine a misty mouth, ew!) rather than a thin film on the surface. So saliva, which contains surface active substances otherwise known as surfactants, breaks down the surface tension (higher surface tension = higher grip hold for droplets) and promote a thin film rather than droplet formation

Chunky read? Hang in there, it isn’t all that difficult…

4. So why is Eugene’s ‘chendol’, or guys in general have better defogging powers in their spit?
The best surfactants in our saliva is actually from deep within our lungs that moist and mucus line our alveoli (small air spaces) to prevent it from collapsing by reducing surface tension. Girls in general, tend to spit in the girliest ways possible usually with pursed lips and a ‘pui’ effect to be as glam as they can be thus gathering only the predominant saliva present in their mouths. Guys on the other hand, gung ho and macho or so they claim, are more inclined to spit with a lot of guttural “back of throat, old man snort clearing” noises and end up with more lung fluid in their masks i.e. fluids with more surfactants.

Moral of the story: Guys, lend your spits. Girls, be a little manlier, you’ll dive better.

5. But spit stinks, are there any substitutes?
Heaps! As what some of us already use, a variety of commercial soaps, toothpastes, shampoos, detergent, alcohols and glycerine has proven to be of the same effect with the common denominator of being a wetting agent which will lower the surface tension of the mask. Baby shampoo in particular because it has a no-tear formula but why waste the money when spit is ample, endless and free! And you won’t risk losing your bottle of surfactant on a mambo jumbo mess of equipment on board the boat.

6. Additional trivia?
Rubbing the spit in, or any other surfactant for that matter not only spreads the gunk out evenly but also cleans the mask off grim, dirt and crystallized salt. Remember, the more even the surface, the lesser chances of it fogging.

Also, as we explained earlier, the best forms of natural surfactant are from our lungs. However, horrible diseases resulting from surfactant deficiency (such as breathing problems of premature babies) demands an external source of surfactants so doctors use a genetically engineered artificial surfactant from freshly pureed specimens to help treat this problem. Think about the best of the best of mask defoggers and this would be it. Mask clearing skills will soon be a thing of the past. But if so, the cost of this product would bankrupt poor Equator Dive or any average scuba trip for that matter. Likewise, most divers would gag and scoot at the prospect of including a selection of small pureed sacrificial animals to act as surfactant donors on their next dive trip. But it is a thought nonetheless…

*Article written by Divemaster Gloria Ngoi and edited by Divemaster Grace Loo