You know what’s not fun? Wearing a face mask to help slow the spread of COVID-19 like a responsible citizen, and then getting fogged-up glasses. Yes, we’d rather get foggy glasses than catch or spread this unprecedented virus—or go against CDC recommendations to wear a face covering in public.
Back in 2011, two scientists published a study in the Annals of The Royal College of Surgeons of England that illuminates a simple, at-home hack for this very phenomenon, which “can be a nuisance and even incapacitate” medical staff. Anti-fogging spray products do exist, but this trick requires zero shopping and adds no risk of putting harsh chemicals near the sensitive eye area.
Here’s how it works: Right before putting on a face mask to head to the grocery store, wash the glasses with soapy water and shake off the excess. Then, let the glasses air dry or gently dry off the lenses with a soft tissue before putting them back on. Now the lenses should not mist up when the face mask is worn.
How simple is that? But it’s scientifically sound, promise. As study authors Sheraz Shafi Malik and Shahbaz Shafi Malik explain, wearing a face mask directs warmer, exhaled breath upward (rather than outward, like normal) where your glasses sit. The warm water vapor condensing on the cooler surface of the lenses causes them to form tiny water droplets and get misty. “The droplets form because of the inherent surface tension between the water molecules.”
The soapy water’s sneaky role, then, is to leave behind an undetectable surfactant film that reduces said surface tension and allows these water molecules “to spread evenly into a transparent layer.” The authors also note this unassuming trick, or “surfactant effect,” can be used in any day-to-day attempt to prevent fogged-up glass surfaces.