In alt.home.repair, on Sat, 17 Oct 2020 07:18:03 -0700, Bob F
wrote:


The idea is to have a very thin film of soap left on the lens. It keep
condensed water on the lens from forming tiny droplets, which form the
fog on the lens. Instead, the water forms a very thin film which doesn't
block vision so much and evaporates quickly. The same principle probably
prevents the water spots. You can also just rub wet fingertips on a bar
of soap and rub the soap paste on the lens, then wipe it off with cloth
or tissue until the lens is clear. You just want to leave an invisible
film of the soap on the lens.

There are also anti-fog products available commercially.

I used to use one of those anti-fog products, from a little plastic
bottle. Now I guess it was just soapy water. I'm glad I didn't pay for
it, got it free somewhere iirc.

But I don't have the fog problem, even when wearing an n95 mask and my
reading glasses. Maybe my mask doesn't leak at the top. It's somewhat
stiff and has the metal nose band inside.