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My bathroom is not very large, and especially during winter, the mirror tends to fog up after the shower has been in use. Is there something I can do to avoid the mirror fogging up? I seem to vaguely recall that surfaces can be treated to be more hyrdophobic / hydrophilic, but I'm not sure that applies to mirrors. Plus, maybe there's something else other than a mirror treatment I haven't thought of...

Note: Not related to this question, where the fog-up is independent of shower use; I'm talking about when the humidity is very high and the temperature has risen as well.

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  • is the exhaust fan broken
    – Traveler
    Sep 14, 2022 at 17:48
  • Even with the exhaust fan running, my bathroom mirror will fog up. You could open a window, or leave the bathroom door open (subject the the presence/objections of house mates). Or, just wipe it dry with a hand towel when your shower is done.
    – FreeMan
    Sep 14, 2022 at 17:51
  • Plastic mirrors come up to temperature much more quickly (though they are also easily scratched) and are common for "shaving in the shower" mirrors for that reason, and because they don't shatter and cut you if they fall. Which isn't what you asked, but other than more ventilation, it's an option.
    – Ecnerwal
    Sep 14, 2022 at 18:04
  • @Ruskes: There's no exhaust fan, only a window, that's closed during use...
    – einpoklum
    Sep 14, 2022 at 19:03
  • @einpoklum soap would make it more hydrophobic, just spray some on, not to much so it runs, you can wipe it off afterwards
    – Traveler
    Sep 14, 2022 at 19:07

5 Answers 5

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Mirrors fog up because they're (with few exceptions) made of glass, which is cool and encourages warm moist air to condense on the glass surface.

If you can eliminate some warm moist air, that will help. Exhaust fans, open windows, or lowering your shower water temperature are common ways to improve this.

On the other end of the issue, if the glass is not cool but warm, condensation will be less likely and less severe. There are resistive heaters for mirrors that warm the glass, or someone else has suggested using plastic mirrors instead of glass. A smart mirror project I saw a while ago used hot water circulating behind the plastic mirror surface to warm the glass and prevent condensation.

These options will increase energy costs, so you'd have to determine if that's worth it for you.

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There are many "anti-fog" heated mirrors on the market now. So, replacing the light and mirror with a lighted heated mirror would be one way to solve that problem.

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  • Wouldn't that need a power socket somewhere?
    – einpoklum
    Sep 14, 2022 at 22:12
  • 2
    @einpoklum If you have a light above the sink, the idea is to replace both and use the power from the box behind the light. Sep 15, 2022 at 0:46
  • That makes sense, and perhaps you should edit it into the answer.
    – einpoklum
    Sep 15, 2022 at 13:40
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When I shower I always leave the door open and/or a window; the mirror experiences almost no fog this way.

I also dislike scorching hot showers so the lower water temperature helps.

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The mirror fogs because of condensation. Condensation happens because of dew point: water vapor in the air will condense onto any surface that is cooler than the dew point. It is condensing on your walls too; you just don't notice it there because the walls aren't mirrors!

There are only two ways to prevent the fogging. One is to keep the dew point lower, ie to keep the humidity lower. In other words, increase ventilation. The other way is to heat the surface to ensure it stays warmer than the dew point. A fan blowing on the mirror, especially in the form of a heater like a hair dryer, is warming the glass. An electric heating mat could be installed behind the glass as well.

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  • Indeed, there's lots of condensation on my wall tiles.
    – einpoklum
    Sep 15, 2022 at 13:39
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If open window or open door are not the choices.

If you like get one of those fancy looking small fan and let it blow at the mirror.

Choose a color that matches your bathroom, so it looks decorative.

Choose size, I would suggest not larger than 5 inch.

I found some on Amazon.

Alternative : soap would make it more hydrophobic, just spray some on using mist sprayer (not regular), you can wipe it off afterwards

source amazon

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  • I use shaving cream, works great!
    – Gil
    Sep 14, 2022 at 22:14

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