Fogged up mirrors

Article 6 Module 2

Misted breath two morals

Misted breath two morals

Fogged up water molecules

  • Cold misty breath looking like a miniature cloud

  •  Fogging up our eyeglasses

  • Steam that fills the bathroom that is as light and airy as an ultra-fine spider’s web. 

  • Fogged up bathroom mirrors 

All those instances of “fogged up” water molecules are those of water vapor cooling down to something that is not liquid water.

They are cooled down water vapor molecules. 

Fogging and antifogging

Fogged up mirror, except over the sink

Fogged up mirrors

Fog is clearly made up of water molecules. When studied, one can see microscopic droplets of water. In fact, the droplets can be as small as 1/500th the size of a raindrop.


But fog does not feel like small raindrops any way you look at it.

For example, suppose we squirted water from a fine nozzle onto a mirror. We can see ourselves in the mirror in-between the droplets.

But we cannot see ourselves if we fogged up the mirror!

Droplets on the glass

Droplets on the glass

Take an analogy of spray painting

As an analogy, take watercolor paint – any color.

 Spraying paint through an atomizer would produce ultra-fine droplets of paint; light can still pass in-between the droplets. 

However, use a paint brush to produce a thin layer of paint: the paint granules are all connected together. 

A paint stroke does not allow light to go through.

Notice the difference: even if finely misted droplets of paint are quite small and densely packed, they have a different configuration from a paint stroke.

Two physically different ways of coating a surface with paint.

The difference between fog and finely misted water is the following:

In fog, there are water vapor molecules that are holding hands.

This will be discussed further in the next lesson.


Fog webbing of water molecule

Fog webbing of water molecules, Oxygen large blue circles; hydrogen small red circles


Fog, mist, cool breath, and visible steam are the result of water vapor molecules

that have cooled down and formed a web

of interconnected molecules.

Picture credits:

  1. 1. Nathalie Owen. Fog o'er the Mountainside. Flickr photo-sharing. Taken on Dec 27, 2013.
  2. By nik7ch. Shutterstock. , Stock photo ID: 30565345. Early in the morning, two morals left on glade.
  3. melanie_ko. Amazing invention - the part of the mirror above the sink does not fog up! Flickr photo-sharing, taken on Feb 28, 2013.
  4. blairwang. Droplets on the glass. Flickr photo-sharing. Taken on June 8, 2008.
  5. By Laura Fearn. In fog, the primary element is the hydrogen-bonded interconnected water molecules. These form a three dimensional web of molecules. December, 2018.