how soap works
Susanna Laurén Feb 20, ’24 ~ 2 min

How soap works?

In our daily routines, we often reach for a familiar item to help us tackle the grime and grease that accumulate on our clothes, dishes, and skin: soap. This seemingly simple product goes by various names and comes in numerous forms, yet its purpose remains constant—to cleanse. Whether in bar, liquid, or powder form, soap plays a crucial role in maintaining cleanliness and hygiene in our lives. But have you ever stopped to ponder how this humble cleaner actually works its magic? In this blog post, we delve into the world of soap, exploring its composition, mechanisms, and the fascinating science behind its ability to rid surfaces of dirt and impurities. 

What is soap?

Soap is a salt of fatty acids such as sodium stearate or sodium laureth sulfate. Fatty acid salts are molecules that have hydrophobic carbon tail and hydrophilic head groups. This will make molecules’ surface active meaning that they arrange at the air-water interfaces so that the hydrophobic tail is in the air and the hydrophilic head is in the water phase. When there is an excess amount of these molecules in a solution, the surface becomes saturated, and the molecules will arrange themselves into micelles. Micelle is like a reservoir of soap molecules, where hydrophobic tails are pointing inwards and hydrophilic head groups form a shell around it. The concentration at which micelle is formed is called critical micelle concentration and is an important parameter when cleaning formulations are developed. 


Soap in action

The hydrophilic and hydrophobic parts of the soap have a crucial role in the cleaning process. Typically, the dirt that is removed from our clothes and dishes is hydrophobic grease. When soap molecules in water come in contact with grease, they arrange themselves so that hydrophobic tails are inside the grease and hydrophilic heads point towards the water. While doing that, soap molecules decrease the adhesion force between the dirt and the substrate leading to less external work e.g. rubbing required to remove the dirt.   

Soap in action


Related products

   Sigma CMC Fully automated critical micelle concentration (CMC) determination with high  accuracy.


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