You are walking down the street on a cold winter day and suddenly your glasses fog up when you breathe through your mask. Ahh! What did just happen?

This is one of the most common day-to-day problems faced by people wearing glasses (including me). So, let us see in this article, why the glasses fog up and also how can we prevent them from fogging. So, let’s get started.


Why glasses get foggy when we wear a mask

Let us say the temperature outside your home is very low (around 22 Degree Celsius) and you wanted to go out shopping. As you move in the cold weather, your spectacles start becoming cold. They have now become so cold that the warm air which is coming from your nose through the mask condenses on your glasses. This causes the fogging of your glasses.


Fog is a form of condensation which occurs when warm air hits a cold surface.


If we look at the physics behind it, First the glasses are becoming cold due to the cold weather outside. Secondly, the mask is directing the warm air from your nose to your glasses. Finally, the warm air from the nose condenses on the cool surface of the glass which is below the dew point of the warm air.


Similar Cases

The fogging of glasses is not limited to masks. We can see this flogging in several places including:

1. When we walk out of the AC (Air-conditioned) Room to an unconditioned room.

2. When we walk inside a warm room from the outside on a cold winter day.

3. When we wash dishes with hot water, the warm water vapor condenses on the cold glasses.


How to prevent foggy glasses

1. Wear your mask properly. Tighten the nose clip such that the warm air doesn’t reach the glasses.

2. Wash your glasses with soap water (liquid soap or detergent). Scientific studies found that a thin layer of soap on the glasses prevents fogging.

3. You can use anti-fogging sprays which are available in the market.



Fogging is a very annoying but unavoidable natural process. But we can use the methods mentioned in the article to prevent fogging your glasses.





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