Hydrophobic Lenses on Sunglasses
Hydrophobic Lenses
Hydrophobic lenses are one of the most important elements to surf sunglasses. You do not have to be a Greek major to understand what hydrophobic means. Hydro = water. Phobic = fear of. Hydrophobic lenses are “scared of water” or more appropriately, repel water.
The Limits of Hydrophobic Lenses
Hydrophobic lenses are not perfect. They do not completely clear of water every time you dunk you sunglasses, but they do much better than ordinary lenses. The hydrophobic coating is the last layer to go onto the lens – if any film (like the oil from your hands) gets on the lenses, the hydrophobic coating becomes ineffective. It is important to clean the lenses well before heading into the sea and not touch the lenses with your fingers when you are surfing. It is advisable to carry a microfiber cleaning cloth in your board shorts so you can clean the lenses while surfing.
Hydrophobic coatings do very well against lenses that are submerged in water, but they are largely ineffective against tiny particles of spray. On very windy days you may want to leave your surf sunglasses at home.
Hydrophobicity in action: The water prefers to bond with itself rather than spread out across the surface of the leave
All Surf Sunglasses sold at WearSurfGlasses.com have hydrophobic coated lenses.
How do Hydrophobic Coatings Work?
A water molecule is polar and tends to be attracted by other polar molecules, notabley other water molocules. This phenomenon creates surface tension – instead of covering a surface evenly, limited quantities of water tend to form individual drops.
Hydrophobic molecules are neutral and non-polar; they are happy all by themselves, they don't attract anything. Water is more attracted to itself than to a hydrophobic surface so an individual water drop on a hydrophobic surface will “cling to itself”. This creates a high contact angle (see image). Because of this the contact area of the drop on the surface is minimized, limiting surface friction. Since hydrophobic surfaces do not form bonds with water and they limit friction they send water off the lens better than normal materials. Perfect for surf sunglasses lenses!
Other Benefits of Hydrophobic Lenses
Hydrophobic surfaces are also anti-static. Dust and other dirtying particles are not attracted to them and sometimes if they do happen to collide they just fall right off. When they do get dusty and dirty they clean easier than lenses that do not have hydrophobic coatings.
Maintaining Your Hydrophobic Lens Coating
The hydrophobic coating is a microscopically thin film. It’s important to clean your lenses before surfing so that there are no molecules on top of the coating to disrupt its function. However, you have to be careful not to destroy the hydrophobic coating through over-aggressive cleaning, cleaning with rough materials (use a microfiber cloth), or using chemical detergents. If your glasses are well cared for, the hydrophobic coating should stay in good shape for at least a couple of years. If it has become worn out, email me (Tony@WearSurfGlasses.com) - I have replacement lenses for most of the water sports sunglasses I sell.