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How Do Fog Free Mirrors Work? (And Why Do They Fog Up?)

how fogless mirrors work

If you have always hated dealing with bathroom mirrors that fog up after your bath, shower, or when you run the hot water in your sink, fog-free mirrors are for you. These mirrors can help save you time when you are in a rush, and they are simple to use.

Why does your bathroom mirror get foggy?

Bathroom fog is small droplets of water in the air. When hot water exits the plumbing, it is warmer than the air in the bathroom. The water interacts with the cooler air, becoming gaseous steam.

The steam builds in the air to the point that it reaches the surface of your bathroom mirror. That surface is cool, causing the gas that makes contact with it to cool. It condenses on the mirror, fogging the mirror’s surfaces and reducing visibility.

A fogged mirror will become clear once the air holding the steam cools down. You can also wipe the surface of your bathroom mirror, but the fog will usually return almost immediately.


How do anti-fog bathroom mirrors work?

The most effective design is the Fog-Free Mirrors that use heating elements. It connects to your mains, often wired to a wall switch that turns on the heating elements when the bathroom light comes on.

The heat generated reduces the temperature difference between the mirror’s surface and the fog from the hot water. That prevents water from collecting on the mirror, keeping it reflective and allowing you to see it.

This system has advantages that include:

  • most effective anti-fog treatment
  • Instant results
  • Consistent coverage across the mirror

It requires hardwiring, which is out of reach for many DIYers. That can increase the cost if you are installing the mirror as an upgrade in a finished bathroom. The system needs to be activated, so you need to turn on the lights (or the separate switch) to create the anti-fog surface.

Another technology available to you is fog-free glass. The design does not use heating elements. The glass on the mirror provides a barrier that reduces fog build-up or eliminates it.

The fog-free barrier can be part of the glass itself. It can also consist of a permanent coating that is placed over the glass during the manufacturing process.

Some of the advantages when using this method include:

  • Easy to install
  • Cheaper price tag
  • A larger variety of sizes available

Most mirrors using this type of anti-fog technology can still fog a little bit. Higher quality materials improve overall function, but heating elements will always provide better protection against build-up.

Shower mirrors

For some, the shower mirror is an economical answer to fogging issues in their bathroom. These are small mirrors that you can use as you shower. Simple designs, like the HoneyBull Shower Mirror, use suction cups to attach to the shower wall.

These products use the anti-fog glass or coating previously discussed. You usually get what you pay for, with cheaper designs providing limited results.

Steps to help keep steam from building up

  • Use your bathroom vent
  • Bath, shower, or wash with cooler water
  • Crack or open the bathroom door

Your mirrors will not fog up if you can prevent the drastic temperature changes between the moist air and the mirror’s cooler surface.

Most homes come with bathroom vents. Switching the fan on before you turn on the water will pull the humid air out of the bathroom as it builds.

You can also reduce the amount of steam generated by turning down the hot water. Using cooler water as you clean will help with keeping your bathroom mirrors fog-free.

If you are not worried about privacy, you can also leave the bathroom door cracked (or wide open). That will allow the humidity to escape while you shower. It also reduces the time your mirror takes to recover from fogging.

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