Soap or detergent molecules have two chemical groups. One of them is hydrophilic “head”, while the other is hydrophobic “tail”
Most parts of dirt are oily and organic in nature, so they don’t dissolve in water. •When soap or detergent get contact with the dirty clothes or hands in presence of water then the hydrophobic part runs away from water, and is attracted by the oil or the other dirt, So it makes micelles contain dirt inside them.
When rinsing with a large amount of water, all of these micelles carrying fat and dirt will be disposed off.
When no more dirt exist, hydrophobic part will not find any place to go except air. Air micelle will be formed, instead of oily one. and it will fly away toward the out air, after it has been surrounded by outer layer of soap, where as, hydrophilic is still attached to water. This is bubble.
So there is no foam when the hands are still dirty. But they add anti-foaming agent to the washing machine detergent.
Generally a defoamer is insoluble in the foaming medium and has surface active properties. An essential feature of a defoamer product is a low viscosity and a facility to spread rapidly on foamy surfaces. It has affinity to the air-liquid surface where it destabilizes the foam lamellas. This causes rupture of the air bubbles and breakdown of surface foam
Prepared by: Pharmacist. Ruba Noueddin