Those who wear glasses sometimes complain that wearing a mask causes their glasses to fog.
Tips on preventing glasses from fogging up come from several sources, including information shared for actors who wear masks on stage and for doctors who wear surgical masks.
“Typing a surgical masks to prevent fogging,” by D.J. Jordan and R. Pritchard Jones, suggests crossing the ties of a surgical mask to create a better seal at the nose. The standard technique for tying a surgical mask involves knotting the two ties so they lie above and below the ear in a near parallel appearance, the authors explain. They suggest knotting the bottom ties above the ear and the top ties below the ear to create a criss-cross, which causes the top of the mask to fit more snugly on the nose.
“A simple method to prevent spectacle lenses misting up on wearing a mask,” by Sheraz Shafi Malik, suggests: “Immediately before wearing a face mask, wash the spectacles with soapy water and shake off the excess. Then, let the spectacles air dry or gently dry off the lenses with a soft tissue before putting them back on. Now the spectacle lenses should not mist up when the face mask is worn.
“The face mask directs much of the exhaled air upwards where it gets into contact with the spectacle lenses. The misting occurs from the warm water vapor content condensing on the cooler surface of the lens, and forming tiny droplets that scatter the light and reduce the ability of the lens to transmit contrast. The droplets form because of the inherent surface tension between the water molecules. Washing the spectacles with soapy water leaves behind a thin surfactant film that reduces this surface tension and causes the water molecules to spread out evenly into a transparent layer. This ‘surfactant effect’ is widely utilized to prevent misting of surfaces in many everyday situations.”
Sewing a wire inside the top of a cloth mask also helps the wearer adjust the fit to prevent their moisture-laden breath from coming out the top of the mask and fogging their glasses. Many hobbyists use pipe cleaners, but there are also wire nose pieces designed specifically for this purpose.