What Percentage of surfactant is in solution of shampoo when we apply it to hair?

For example a Shampoo has 15% surfactant. When we use it, it is diluted with some water already in hair. So at this stage usually what percentage if surfactant is there in that dilution?

Comments

  • PerryPerry Administrator, Professional Chemist
    Depends on how much water is in your hair when you apply it. I would guess you have 2/3 shampoo and 1/3 water ratio so that means about 10% surfactant.
  • AbdullahAbdullah Member
    edited October 19
    @Perry i got your point. 

    I have experienced that if you apply shampoo to dry hair it doesn't foam well and if you apply a Shampoo with high surfactant percentage like 20% it foam but if you add some extra water on hair after applying shampoo the foam increase a lot. It means there is a certain range of surfactant percentage in water that foam to maximum. If it is too diluted it doesn't foam well and if it is not enough diluted it doesn't foam well. So what is that percentage range of surfactant in water that foam most? 

    One way to find this may be be to make several samples with 1,2,3,4,5,6,7,8,9,10% surfactant and apply each to dry hair and see which one foam better. But if someone knows that it will same me time and everything. 
    Thanks
  • PerryPerry Administrator, Professional Chemist
    You are correct that there is an optimal level of surfactant/system : water ratio to achieve the best foam.  That will be different for the different systems.

    When we did foam testing we tested 5ml of shampoo to 100 ml of water. Doing the math that would have been about a 0.5 - 1.0% surfactant:water ratio, depending on the formula tested.  But our testing was done in a blender. You would put in the water & shampoo, then mix the blender at a set speed for 1 min.  Then you would measure the foam height.

    That would give you more consistent results than testing on hair tresses.
  • @Perry thanks.
    That percentage is a good start point
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