savon de rasage

How is soap foam created?

Do you sometimes find yourself faced with soaps that don't lather? Do you like mousse? But have you ever been interested in the science behind this foam? And why is it useful for shaving?


How to create foam?


As children, we had fun blowing soap bubbles; All you had to do was mix dishwashing liquid with water, dip a circle, and blow. But how do these bubbles work and what are they made of?


The soap is made up of two parts: a head which loves water and repels fat, and a tail that loves fat and repels water. Two opposites. This is where the washing power of the soap comes from: the tails trap the greasy parts, and the heads cling to the water when rinsing, thus getting rid of the greasy parts. This sphere of soap molecules trapping a fatty substance is called a micelle.

We find this cleaning power everywhere in our daily lives, whether in the dishwasher tablet or in the shampoo. However, how are the bubbles created in all of this?

A soap bubble is actually air trapped in a layer of water and soap. This thin layer of water is itself surrounded by soap molecules. Soap bubbles therefore appear when air is agitated in the presence of soap and water. Without air, it is not possible for the bubble to trap air.

Micelle

What about the foam then?


From a scientific point of view, foam... It's gas bubbles separated by a liquid! The foam created by soap in our daily lives is therefore air bubbles separated from each other by a liquid, often water. Foam is millions of air bubbles attached to each other by a continuous film formed of water trapped between two layers of soap molecules. 


And shaving in all this?


Soap foam has a very important role to play in classic shaving, thanks to its water content. Since foam is water between thin layers of soap, the more foam, the more water. The denser the foam created by the soap, the more water there will be (constituting the continuous film), and the less air there will be. Water is essential in a quality shave, because it softens the hair which becomes soaked with water, and it prevents dehydration of the skin.


In short, you already know a lot about foam, but don't forget one thing: for it to clean, it doesn't have to foam!
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