How is soap foam created?

Do you ever come across soaps that don't lather? Do you like lather? But have you ever been interested in the science behind it? And why is it useful for shaving?


How do you create lather?

 

As kids, we used to have fun blowing soap bubbles by mixing dishwashing liquid with water, dipping a circle, and blowing. But how do these bubbles work and what are they made of?


Soap is made up of two parts: a head that likes water and repels fat, and a tail that likes fat and repels water. Two opposites. This is where the washing power of soap comes from: the tails trap the greasy parts, and the heads cling to the water when rinsed, allowing the greasy parts to be removed. This sphere of soap molecules trapping a greasy substance is called a micelle. 

We find this washing power everywhere in our daily life, whether it is in the dishwasher tablet, or in the shampoo. However, how are the bubbles created in all this? 

A soap bubble is actually air trapped in a layer of soap and water. This thin layer of water is itself surrounded by soap molecules. Soap bubbles 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 foam?

 

From a scientific point of view, foam is... gas bubbles separated by a liquid! The foam created by a soap in our daily life 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 of water trapped between two layers of soap molecules. 

How is this related to shaving?

 

Soap foam has a very important role to play in conventional 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 (forming the continuous film), and the less air. Water is essential in a good shave because it softens the hair that becomes waterlogged and prevents dehydration of the skin.


In short, you already know about lather, but remember one thing: it doesn't have to lather for it to clean!

Leave a comment