Background Info

 1.    Q) How does shampoo work? 
        A) Pure water alone is not quite enough: removing dirt, which is soluble in fat (lipophilic)  requires a surfactant. Surfactants are the essential cleaning substances in shampoos. 

    Surfactants are active cleansing substances that consist of a fat-soluble (lipophilic) part and a water-soluble (hydrophilic) part. The lipophilic part sticks to oil and dirt, and the hydrophilic part allows it to be washed away. 

    There are a few types of surfactants but these are the most commonly mentioned on shampoo labels: ammonium lauryl sulphate and another is ammonium laureth sulphate, which is milder.

Blue Particles-Surfactant Molecules      Pink Particles-Conditioning agents
Unclean Hair Surfactants lift Dirt Conditioning Agents Released Conditioner Smoothes Hair
Conditioning agents build up on the hair if shampoos aren't used regularly and repeatedly.
Shampooing always removes the conditioning agents that were applied previously.*
 Surfactant molecules and conditioning agents surround the hair; each conditioner particle is trapped inside a crystal 'cage'.*
 When the hair is rinsed, the conditioner particles are released from their 'cages'; they are not washed away but, because of their positive(+) electrical charge, they are drawn towards the negative(-) charges of the hair.*

 They cling to the hair, smoothing out any roughness on the surface and protecting the cuticle.*

  2.     Q) What is hair made up of?
      
A) Hair is made up of a tough, hard protein called keratin. Keratin makes up other things in the body as well like fingernails and toenails, even skin has keratin in it. Also, each strand of hair consists of three layers.

  3.     Q) How does Hair get Oily?
      
A) Hairs on the head are lubricated by a natural oil called sebum which is produced by the sebaceous glands of the follicles. How much natural oil your glands produce is mostly determined by your genetic inheritance. However, in many teenagers, a massive increase in hormone levels leads to raised grease production. This results in a tendency to have greasy hair, but this is very common. The good news is that most of them outgrow it.

Diagram of Hair Root

 
4.      Q) How does hair get shiny?
            A)  Probably the most obvious aspect of healthy hair is its shine - its ability to reflect light. This mainly depends on the cuticle of the hair shaft, and how secure it is. (The cuticle is the thin, colorless layer that protects the cortex)
    So the good condition of your hair actually relies on the current state of each of the 100,000 or so individual hairs on your head. If the cuticles are secure, if their cortex has not been affected by heat or chemicals, and if the hair is not covered with grease and/or old hair spray, then the hair will probably have reasonable shine and body.

 
5.      Q) How does the pH level effect how well the shampoo works? 
       
A) The pH of a substance indicates its overall acid/alkaline level (above 7 is alkaline, below 7 is acid). Sebum, the hair's natural oil, has a pH level of about 5.
Most shampoos range between pH 5 and pH 7 although anywhere between 4 and 9 is just fine for a good shampoo. Too much alkaline in shampoos can strip away too many natural scalp oils and extract the "glues" that help hold the hair shafts together. Experts say that these high pH alkaline shampoos make your hair look great for a few weeks but then cause the hair to become dry and brittle which increases the breakage of your hair.  (As part of our experiment we tested the pH levels on the shampoos that we used.)

pH Scale with Examples

*the pictures came from the Procter and Gamble Web site