Why Do Divers Spit In Their Masks?

Why Do Divers Spit In Their Masks?
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When you join your first diving class or see your friends getting ready for a big dive, you might be astonished when you see them spit into their masks and rub it around before putting the mask on.

Divers are used to this phenomenon. Even if they are used to it, however, not all divers understand why it works. Most know that it helps to prevent fog from building up in the mask while diving, but a few know why this method works.

Why do divers spit in their masks? Let’s investigate this common defogging technique, why it works, and the alternatives that you might find more appealing.

Why Do Scuba Masks Fog Up?

Temperature and Dew Point Balance

Scuba masks get fog on the inside for the same reason that your car window does when you are driving down the road on a fall morning. It is because of the balance of temperature and dew point.

When the temperature of the air inside of the lens is below the dew point, then water will condense on the inside of your scuba mask. Your eyes cannot see them, but the inside of your mask surface is covered in microscopic indentations. The condensed air will naturally attach itself to these indentations, leading to the fogging that all divers are familiar with.

While the fogging up of your mask is not inherently dangerous, the foggy film can make it difficult or impossible to see. This makes a dive much less enjoyable because you cannot see the world around you as well. Additionally, it can be dangerous not to be able to see your gauges as clearly as you should be able to while diving.

Fresh Mask Fog

Another reason that a mask might fog is that of leftover particles from the manufacturing process. Before you use a mask for the first time, it is always advised that you treat the inside of the mask to prevent this from happening.

While some divers use heat to do this, the easiest method is probably to use non-gel toothpaste. By simply rubbing toothpaste on the inside of the mask, rinsing it off, and repeating a few times, you can ensure that no particles are left. Unlike the burning method, this technique doesn’t risk any damage to the mask.

Why Do Divers Spit in Their Masks?

The best way to get rid of or prevent fog is to decrease the surface tension of the water droplets that would otherwise become a foggy field. Rather than be able to stick to every little micro-indentation, the condensed water will instead form into larger droplets. These droplets can simply roll off of your mask.

Solutions that can break up and lower the surface tension like this are called surfactant. Saliva can act as a surfactant, and that is why divers spit into their masks. While there are many other options that you could use instead (which we will talk about below), most divers would say that nothing is as readily available or as free as spit for this purpose!

Treating Your Mask Before A Dive

It’s important always to treat your mask before you go for a dive. This is because you would want to prevent fog from occurring before you get into the water. In this way, you do not have to fight the fog every now and then throughout your entire dive.

Here are some of the most common methods of preventing fog, including the ever-popular spit technique!

#1 Spit In It

Spit into your mask, and then rub it around. After doing this, dip your mask in water before putting it on. This method is only effective if the mask is still wet when you start the dive, so be sure to do this just before you enter the water.

#2 Defogging Sprays

There are a number of commercially available products that fight fog in scuba masks. They are used in a very similar way to spit. Simply spray the recommended amount inside the mask and dunk it in fresh water just before starting your dive.

#3 Baby Shampoo

If you don’t want to use spit, but you also don’t want to buy a scuba-specific product, you can use baby shampoo to defog your mask. Use it in the same way as spit or sprays.

While it is possible to use regular shampoo in the same way, baby shampoo is preferable because it is less irritating to your eyes. Additionally, most baby shampoo is biodegradable, so it is better for the environment.

#4 Toothpaste

Just as you can use toothpaste to get rid of manufacturing leftovers, you can also use it to prevent fog before a dive. Use a non-abrasive, non-gel toothpaste. Rub it all over the inside of the lens. Then, rinse until the water is clear.

One thing that should be noted about this particular technique is that the minty aroma of some toothpaste can be irritating to your eyes and cheeks. If you decide to use this method, test it out in a controlled environment to make sure this won’t be an issue for you before diving.

Other Tips To Keep Fog Out

Even after you have used one of these fog-prevention methods, you may still find that fog plagues you while diving. There are a few reasons for that, and these tips can help ensure that you don’t have to deal with a foggy mask.

  • Rinse your face off before putting your mask on if you are hot or sweaty.
  • Do not take your mask off, put it on your head, or hang it around your neck after applying your chosen surfactant.
  • Make sure that your lens is completely dry before you apply your chosen defog tool.

Final Thoughts: To Spit or Not To Spit?

Why do divers spit in their masks? Well, it’s simply because it’s the most easily accessible way to prevent fog from forming in your masks! That being said, it is not the only method. The decision about whether to spit or not to spit is ultimately up to you, so you do not have to use this old-school method if you do not want to.

Remember, however, that if you should ever forget your defogging product, you have a backup solution available to you at all times—your spit!

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