Deep-Six Underwater Systems, Inc.
"Add Depth to Your Life"

Table of Contents

1 Pressure and Gases
2 The Face Mask
3 The Snorkel
4 The Fins
5 Weight Systems
6 The Knife
7 The Wetsuit
8 Pressure and Water
9 The Ear and Pressure
10 The Sinus and Pressure
11 The Stomach/Intestine and Pressure
12 The Lung and Pressure
13 Barotrauma caused by External Air Spaces
14 The Buoyancy Compesation Device (BCD)
15 The Scuba Cylinder
16 The Scuba Cylinder Valve
17 The Regulator
18 Density and the Diver
19 The 4 Gas Laws
20 Hand Signals
21 Carbon Monoxide Poisoning
22 Hyperventilation
23 Nitrogen Narcosis
24 Diver's Flags
25 Sound Underwater
26 Color Underwater
27 Decompression Sickness
28 Breathing Oxygen
29 Deep Diving
30 Thermoclines
31 Thunderstorms
32 Underwater Life
33 Open Water Dives
34 The Final Examination
35 The Environment
36 Advanced Course

2 - The Face Mask

     Diving face masks are crucial to the well being of the sport. It is most important that the mask fits properly. There are several points to look for when purchasing a face mask:

  • To make sure the seal against the face is correct, one should look straight up, put the mask on the face with the strap out of the way, let go of the mask with the hands, and then suck in through the nose. If the mask is drawn to the face, and can be held there temporarily by suction, then it fits!
  • Moustaches commonly interfere with the fit. If they are bushy and there is no skin above them under the nose, air will leak through the hair and cause the mask to leak. Some divers shave the extreme upper part of the moustache. It makes one look more like Clark Gable! Some apply silicone grease to the hair. Some shave the entire thing off.
  • Once the mask fits properly determined by the method described above, then it is necessary to determine whether the size is correct. It would be hard to get a mask that is too large to fit. If you do use a mask that is too large, the strap would have to be so tight it would cause the mask to leave a red ring around the face. It is easy to get a mask that is too small to fit. If the mask is too small the side vision will be reduced. You want to get a mask that allows you to see the most from side to side. And, don't count those side plates found on some masks. When you look through a side plate under water the distortion is so great things seen are not where they really are.
  • Another thing to look for is the volume of the mask. Low volume masks are ones that get your eyes close to the glass. High volume masks have a lot of room in them. For the most part low volume masks offer the greatest vision from side to side. They are easier to clear of water. But, if you have a large face you may have to use a higher volume mask.
  • There are two places masks may caused irritation. The bridge of the nose and the skin directly under the nose. When you try on a mask be sure it does not hit the bridge of the nose (too low a volume), and does not feel the least bit uncomfortable under the nose. A little discomfort in the store will grow to a large pain after an hour of skin or scuba diving.
  • Buy silicone, not rubber. The material will last almost indefinitely. Rubber is rotted by oil. The oil on a diver's face will cause the mask to be useless after a few seasons. Also, the clear silicone masks allow more light to penetrate leading to less tunnel vision.
  • There are two disadvantages with silicone:
    • 1. Silicone will absorb colors from objects touching it. For example, if you attach a rubber snorkel or snorkel keeper to the silicone strap of the mask, the black color will slowly be absorbed into the strap making it look permanently soiled.
    • 2. If mold begins to grow on any silicone material it will embed itself in the material. Even if the mold is killed, the remnants of it may permanently stain the silicone making it very unsightly. Deep-Six has soaked silicone mouthpieces in pure Clorox for days. The mold has been killed but the unsightly color still remained. The mouthpiece was sanitary but it sure didn't look that way!
  • Before the first dive with a new mask it may have to be cleaned of a film left from the manufacturing process that will cause fogging problems underwater. The only way Deep-Six knows to remove this film is with a toothbrush and toothpaste. A vigorous brushing right after purchase is recommended. Don't confuse this first fogging problem with the usual fogging that divers experience on every dive unless they coat the lense with an anti-fogging compound or spit (that is lightly rinsed off) just prior to the dive. One of the better anti-fogging compounds consists of a solution of 50% rubbing alcohol and 50% baby shampoo. The alcohol cleans the lens and the baby shampoo leaves a film that keeps the fog from forming. Baby shampoo will not sting the eyes.
  • Forget buying a mask with a small purge valve. They are hard to use and may cut down on the vision.
  • There are masks that allow the introduction of prescription lenses for a very reasonable cost.

     The principal behind keeping a mask from fogging up during the dive is to get a thin coating of a material to cover the lens without distorting the vision. Spit, shampoo, raw potato juice, commercial anti-fogging products, etc. have a slimy material that will leave a thin layer on the glass. If the diver coats the lens with one of these materials, and gives the mask a light rinse fog should not form as long as the mask does not dry out. It won't underwater, but it will if you coat the lens and then put the mask down while doing something else. The best thing to do is coat the lens last, put the mask on the face, and enter the water. Then let a little water in from the lake or ocean, slosh it around, and then dump it out. All this should be done with the mask on the face. The principle behind fogging is: When a diver breathes out into the mask the moist air hits the cooler glass and little droplets of water form on the lens. This is the fog. If the glass were coated the droplets would just go into the coating and spread out instead of forming a droplet that interferes with vision.

     Be gentle with mask straps. They can and do break when pulled too hard. It's best to put the mask on the face first and then pull the strap down behind the head but not so low it hits the ears.

     Because light has to travel through water, the mask glass, and the air inside the mask before it enters your eye it creates a magnification at close distances (1-15') underwater. Things can appear 1/3 larger and 1/3 closer than they really are. This creates problems for the underwater photographer, spearfisherman, etc. What you thought was a legal catch may get you into trouble when the true fish size becomes apparent after surfacing. It you want to see this effect, put one eye underwater and look at one of your fins that is partially sticking out of the water. Underwater the fin will look larger and closer!

     Clearing a mask of water while underwater is a very important skill. It may sound easy to come to the surface if you get water in your mask just to dump it out. Surfacing from a dive takes time and is inconvenient to you and your buddy especially if it is for a problem that could be easily corrected underwater. So, mask-clearing underwater is a major component of any scuba course. It is a simple process, especially if you are able to breathe underwater. The best method is to place the hand lightly on the top of the mask (this keeps the air from escaping), look straight ahead, and then blow gently through the nose. The water should leave through the bottom of the mask because the trapped air pushes it out. If it does not all go out on the first try, inhale more air and do it again. The position of the head during this is very important. If you look down too far the water will stay against the glass. If you look up to much water will get in the nose when the air is not coming out. Some divers find it easier to open the bottom of the mask slightly WHILE AIR IS COMING OUT OF THE NOSE. This allows the water to exit without having to build up pressure in the mask.

     Since the mask fits so closely to the face and makes a seal, there is the possibility it will be squeezed against the face when the diver descends. After all it is an air space that is going to be crushed to 1/2 its size at 33 feet. If the diver does nothing about this mask squeeze dire consequences may result. The mask is at lower pressure than the pressure inside the diver's body. The excess molecules under the skin will push the skin into the mask. The eyeballs will bulge into the interior of the mask. The pressure inside the skin of the nose becomes greater than the pressure in the nostrils. Divers have come up with a face that looks like it's been battered. In fact, the problem looks worse than it really is. The nose may bleed, the eyes may have blood vessels break so the whites will turn red, and the skin may look like someone slapped the hell out of it. All of this may be avoided by simply putting a little air in the mask through the nose as you descend in the water. Although it would be more hydrodynamic, divers cannot wear goggles while diving because there is no way of pressurizing the inside of them?

     Professional masks for diving are made of glass, not plastic. Glass is hard to scratch. The glass should be tempered. Usually the word, "Tempered" is found on the top of the glass. Tempered means the glass will break in very little pieces rather than in large sharp shards. I have seen a diver fall head first into the ocean off a dock and hit the mask head on. The mask shattered but the diver was not cut (fortunately). Diving into the water with the mask on, dropping the mask in a shower, or packing it tightly in a suitcase may cause it to shatter and become worthless. Placing one hand over the glass lens of the mask when doing an entry is advised.

     Lastly, when you store a mask it is important to not have pressure against it. If you were to pack a mask under a weight, for example, the mask may retain the shape it has been forced into for a prolonged period of time. That is why mask boxes are a wise investment.

Copyright Information about this text, DIVING WITH DEEP-SIX is as follows: Copyright 1996 - 2007 by George D. Campbell, III; President. All Rights Reserved. This file may be posted on Electronic Bulletin Boards for download, but may not be modified, printed for distribution, or used for any commercial purpose without the author's written permission. is using this material with the permission of Deep Six. The full version is available at:
Leisure Pro Gear

Leisure Pro Gear
Leisure Pro Gear