Do you shampoo your hair twice because it foams the second time, but what is causing this foam?
The ingredient present in the product that takes care of the cleaning is the surfactant. The surfactant is a molecule that consists of a hydrophilic head and a hydrophobic tail.
A hydrophilic head binds to the water as it water-loving and the hydrophobic tail binds to the sebum, oil, and dirt because it hates water. Surfactants thus bind to both water and oil and remove the dirt from your hair when it’s washed out.
When there is more surfactant than sebum/oil/dirt, the excess surfactants bind to the water and the water-hating part to air instead of oil. When your washing your hair, small air bubbles start occurring because of the massaging movements you make and these excess surfactants stabilize these air bubbles. If these surfactants are not present, the air bubbles can’t remain for long. Now that the surfactants are present, the bubbles are stabilized and create foam.
Many shampoos contain foaming agents to introduce gas bubbles into the water. Shampoos can clean very well without producing foam and there are shampoos that produce a lot of foam without cleaning well.
There are consumers who think that a shampoo that does not foam properly, won’t clean the hair also. This is not true.
So, should you wash your hair twice?
It’s completely up to you, you can wash your twice if you want, but shampoos that contain anionic surfactants are capable of removing dirt and oil from your hair in the first wash.
If you need to wash twice, that means that it;s really dirty. Also remember that if you do wash your hair twice, the excess surfactant may strip and damage the hair. If you have damaged hair, then a single wash is enough.
Note: If you wash your hair twice, make sure you use a conditioner afterwards.