Why lenses mist up – and how to prevent it

22nd September 2023

Fogged up lenses are the result of condensation, the simple chemical process that occurs when water vapor cools down enough to turn from a gas back into its liquid state. This can happen quite suddenly when there is a drastic difference between the temperature of the lens and the surrounding air. It often occurs when a cold lens is near to your warm face. Close fitting wrap-around sports eyewear is more prone to misting up because the warm air heated from your face  gets trapped behind the lens.

Typical scenarios for fogging up are:

Walking into a warm shop from a cold outdoor (cold lens/warm air). The reverse applies if you step from a cool air conditioned indoors to a warm outdoors (cold lens/warm air).

Putting on a pair of sunglasses left in the car overnight (cold lens/warm face)

Putting on a pair of sunglasses left in a kit bag (cold lens/warm face)

Anytime you’re outdoors and the surrounding air is colder than the heat from your face (cold lens/warm face)

When you wear a mask and your warm, moist breath is directed upward onto your glasses (warm breath/cold lens)   

If your sports eyewear has adjustable nose pads a useful tip is to pull the nose pads away from the lens. This allows more air to circulate around the lens so there is less difference between the temperate of the lens and the surrounding air – so no misting occurs. Some sports eyewear models come with a factory applied anti-fog lens coating – these can be very effective. Safety Eyewear typically has an anti-fog coating applied as fogging up at the wrong moment could be safety critical. There are also some highly effective anti-fog products available to apply to lenses. We sell a few a options. This pocket anti-fog solution from Evolution is very effective and it’s currently on offer.