A mask is needed to create an airspace in front of your eyes so that they can focus as humans have not developed through evolution to focus underwater. Unlike swimming goggles, the nose is incorporated into the airspace of a mask to allow scuba divers and freedivers to equalise both the volume of the mask and also their ears as their volume is compressed by the pressure of the water above them.
The basic construction of a mask is a tempered glass lens in front of the eyes, a silicone skirt to create a seal against the face, a strap to keep the mask secured to the face and a frame structure to fix those components together with. Each of those components can vary in design greatly and each manufacturer will have their own take on what is the best way to do things. Technically speaking there is no difference between a snorkelling mask and a scuba diving mask, one can be used for both activities.
There are some key things to look out for in a mask as a whole including the internal volume and lens angle.
To learn more about masks read down, alternatively go straight to the Scuba Diving Masks department.
The internal volume or ‘profile’ of the mask is important to scuba divers and free divers but less so for snorkellers. The volume is the confined airspace created when the mask is sealed against the face. This space is subject to compression as a diver descends which has to be equalised to prevent discomfort. A very low internal volume is crucial for breath holding free divers as the air to equalise must come from the air held in their lungs so wasting air on unnecessary equalisation reduces the breath hold time. Generally speaking most people find that a lower volume mask is the most comfortable.
Its not always noticed but the lenses and frame of a lot of modern masks don’t run at the same angle as the face and are raked in at the bottom. To a lesser extent this helps to reduce the internal volume but more importantly it improves the lower field of view. By raking the angle the frame is moved back in towards the cheek bones and out of the visible range. Not only does it make looking downwards easier but it benefits snorkeller by preventing the need to tilt the head forward to see below. Tilting the head too far forward will often lead to the snorkel dipping into the water and giving you a mouthful of water.
Each component of a mask will have more advanced features that enhances it to become lighter, softer, improve field of view or increase clarity so lets run though each of the components to look at the features in greater detail. Lets start by taking a look at lenses
Lens configuration and specification present the biggest decision to make. Masks have either a single, twin or multiple lens configuration but the glass specification, lens shape and special coatings are all possible options.
Single lens masks have no frame construction across the bridge of the nose and can seem more open but it is not possible to replacement prescription corrections to these lenses.
Twin lens masks are often compatible with replacement prescription lenses that are made by the manufacturer and are easily fitted following removal of part of the frame.
Multiple lens masks feature a window pane to either side of the mask that help to make the mask feel more open and brighter but do little to increase the field of view as the front lenses generally provide ample peripheral vision.
The lens of a mask should be made from tempered glass. Standard glass shatters into tiny razor sharp shards that would obviously damage the eyes if they were to get into them. Tempered glass is a type of safety glass that has been heat or chemically treated to increase its strength. When tempered glass is shattered it crumbles into larger granular chunks rather than jagged shards.
Standard tempered glass lenses have a number of impurities including iron that gives the glass a green tinge when viewed from the side. These impurities can actually hinder light transmittance into mask by reflecting or scattering the light rays as they pass through the glass but this isn’t noticeable until compared to optical grade lenses. The glass used in high grade lenses has a very low impurity value which allows more light in and also increases the vibrancy of colours.
The shape of the lens is also important. Most manufacturers have adopted a reverse drop shape. If you imagine a water droplet running down a window it has a curved bottom and pointed tip at the top, rotate that 180 degrees and now look at the majority of masks available and you’ll see that shape in the lens. This particular shape works well when used in with a raked frame to offer excellent field of view to both the side and lower sectors and make the frame itself seem almost invisible.
Some masks feature specially coated lenses. The lenses are typically already made from high grade optical glass to reduce the light reflected or scattered by impurities but the additional coatings work to further reduce the amount of light that is reflected back out by the surfaces of the lens themselves.
The mask skirt should always be made from high grade silicone for the best level of comfort and superior sealing. Silita or other plastic based skirts are not as flexible, are prone to warping and are much less comfortable to use.
The role of the skirt is simple but critical, provide a good seal to keep the air in and water out. The one feature that can be found on all good mask skirts is a secondary skirt. The secondary skirt increases the surface that is able to seal against the skin and significantly reduce the possibility of a leak.
As manufacturing techniques improve silicone skirts are becoming more advanced with varying thickness designs and special ridge and dimpled areas to improve fit, comfort and seal integrity. Additives mixed with the silicone are also becoming more common to prolong the life of the skirt and reduce the damaging effect of UV rays.
Masks come in one of two formats, framed and frameless.
Framed masks use a rigid frame which the skirt, lenses, buckles and strap are all fitted two. Generally framed masks are slightly bigger in overall dimensions but the advantage is that these masks can typically be dismantled for cleaning, repair, replacement or to fit prescription lenses. Framed masks are also available in a wide range of colours.
In a frameless mask the silicone skirt is molded around the other components to join them all together. This produces a very slimline mask that can be folded very flat making them ideal as backup masks that can be easily stowed in a pocket. Because the lenses are embedded within the silicone skirt it is not possible to replace them if they break and prescription lenses can not be fitted.
Strap and Buckles
A silicone strap secures the mask to the head and maintains the contact between the skirt and the skin. Using silicone provides a degree of stretch and flexibility that doesn’t hinder movement or affect the integrity of the skirt seal. As everyone is different the strap needs to be adjustable so that it can be tightened or loosened using a buckle system.
A simple buckle system is fixed to the frame of the mask and has a spring loaded flap that grips between the tabs of the strap to allow free tightening but prevent loosening without lifting the flap. These buckles are rigid and no not allow the buckle to swivel or flex with movement.
More advanced buckles can feature easier to use push buttons to operate the strap release rather than have to fiddle with the release flap. Swivel assemblies are common and as a minimum provide vertical movement. In recent years manufacturers have often moved the buckle attachment point off the frame itself and incorporate it further back on to the skirt. Doing this reduces the stress transferred through to the side of the skirt, increases the freedom of movement and helps the skirt seal better.
A mask is a very personal thing. A mask that fits one person may be uncomfortable on another so it is important to find the perfect one for you and not necessarily one that is recommended by a buddy.
It is possible to check for a good fit before using in the water by holding the mask to your face and breathing in through your nose. If the mask stays in place then it fits, if not or you feel air flowing into the mask as you breathe in then try another one for fit. If you buy a mask from us we will send you full instructions on how to perform this test when we despatch your order.
If you have facial hair you can use petroleum jelly or a similar product to help the mask to seal to your face where it comes into contact with the skirt