Having A Good Mask Is The Difference Between An Amazing & A Terrible Dive
Why do we need a mask for diving?
First of all, lets start with why we need a mask for diving. A good diving mask is one of the most important factors that will determine your enjoyment in the water. Whether you are scuba diving, freediving or snorkeling, it is essential to have a mask that is comfortable and does not leak. Nothing is worse on a dive or snorkel than having water constantly leaking inside your mask, or a mask that causes pain.
We as humans need a mask for two reasons. The first is that human eyes cannot focus properly underwater, and require an airspace in front of the eyes to see. The fact that we have an airspace inside the mask leads on to the second reason – to equalize the airspace inside the mask against the water pressure which compresses the air as we descend deeper. A mask covers your nose and allows you to do this, where as swimming googles do not cover your nose, and therefore prevent you from equalizing the airspace in front of your eyes. You may have experienced this sensation if you have swum to the bottom of a swimming pool and your googles push into your eyes more.
Mask structure and design
A mask consists of four main components. A tempered glass lens, a silicon skirt which creates the seal around the face, a frame to hold these two parts together and finally a strap attached to the frame to secure the mask to your face.
Certain features of masks may vary depending what activity it was designed for. Scuba diving masks are generally made of higher quality materials. Freediving masks are also made of higher quality materials but have a lower volume inside the mask, making them easier to equalise. This lower volume means that with some brands and models the vision may be more restricted. Finally snorkeling masks are generally made from cheaper materials and offer a good field of view. Masks can be used interchangeably between disciplines however, but they offer better performance in the discipline they were designed for. The following factors should be considered when buying your next snorkeling, freediving or diving mask.
The internal volume of a mask is how much air is confined in the mask when worn on the face. Scuba divers and freedivers in particular look for low volume masks. These are easier to equalise when descending due to having to add less air into the mask. Freedivers carry only the air in their lungs, therefore every bit of air is precious and lower volume masks can make a difference to performance. Snorkelers will generally be on the surface or duck diving a couple of meters, therefore the internal volume is less important compared to the vision the mask offers.
Mask lenses can be tapered at the bottom towards the cheek bones when viewed from the side, rather than being parallel to the face. This helps to improve the lower field of view, as well as reduce the volume of the mask slightly. By tapering the frame in at the bottom, it moves it out of view when looking downwards which allows for a better head position when snorkeling. This also helps to prevent water entering the snorkel when tilting your head down towards your chest.
As touched on earlier, masks are made from four main components (lens, skirt, frame and strap) and variations in these will effect the comfort, vision and price of the mask.
Mask lenses come in several styles such as single, twin or multiple lenses. Glass specification, lens shape and special coatings are also factor that change between brands and models.
-Single lens consist of one piece of glass across the eyes, with the frame across the nose removed. These offer a good field of view, but may be slightly higher volume, while it is not possible to replace the lens with a prescription one.
-Twin lens offer reduced vision with a frame piece across the nose, but are generally lower volume. The lenses can often be replaced with prescription lenses made by the manufacturer.
-Multiple lens masks feature small lenses on the side of the mask. This can allow in more light, but do not really increase the field of view of the mask. These types of masks are generally used more by snorkelers.
The shape of the lens is also important. Most manufacturers use an upside drop, which when combined with a tapered frame allows good visibility up and down as well as to the side..
A good mask lens should be made from tempered glass. Tempered glass has been treated with heat or chemicals to increase its strength properties. When tempered glass shatters it breaks into large chunks, rather than small sharp shards like standard glass does.
Standard tempered glass lenses also have a number of impurities that gives the glass a green tinge when viewed from the side. These impurities can reduce light penetration into the mask by reflecting or scattering the light rays as they pass through the glass. This only becomes noticeable when 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.
Some lenses also have mirrored coatings, which reduce glare on the surface.
The skirt of a mask prevents water entering the mask and keeps the air in. High grade silicone is the best material for mask skirts, offer good comfort and sealing to the face. Other plastic based skirts or silica are less comfortable and can deform resulting in a poor seal.
Masks with secondary skirts increase the surface area that is able to seal against the face which reduces the risk of leaking.
Silicone skirts are becoming more advanced with varying thickness designs, special ridges and dimpled areas to improve the comfort and seal of the mask. 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.
There are two types of mask frames, framed and frameless.
-Framed masks have a rigid frame which the lenses, skirt and buckle attach to. They can be slightly larger but the advantage is they can be dismantled if needed for repair or cleaning.
-Frameless masks the skirt is moulded to the other components. This allows the mask to be more flexible and can take up less space. The disadvantage of this mask is all the components are moulded together which means they cannot be replaced.
Straps are made out of silicon and are needed to keep the mask attached to the face. They are flexible and allow a certain amount of stretch. Strap covers can be bought to make them more comfortable.
A buckle is needed to adjust the tightness of the mask seal to the face. The buckle is fixed to the frame of the mask and has a spring loaded flap. This allows the strap to be tightened, but prevents loosening without lifting the flap.
Higher end masks feature buckles with easier push buttons, and allow swivel of the buckle to provide more comfort in the position of the strap. Some manufactures have moved the buckle attachment point off the frame to the skirt. This reduces stress on the side of skirt which allows the skirt to seal better
There is a simple test to see if a mask fits your face. Simply hold the mask to your face without putting strap on and breath in. If the mask sticks to your face and you are able to let go with your hand then it is a good fit.
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.
How to prevent your mask fogging up
Brand new diving masks have a thin film of contaminants that collect on the lens during manufacturing. This makes the mask more prone to fogging up, however precleaners can be bought to clean the mask before your first dive or snorkel.
If you experience fogging up consistently then defog spray or gel can be applied before every dive. Other methods include rinsing the mask in sea water, applying spit to the lens when it’s dry and even rubbing it with a potato (only kidding).
How to care for your mask
After each dive, rinse the mask in fresh water. Avoid leaving it in sunlight as this can degrade the silicon skirt.