Before you get into coloring hair, it’s useful to understand the structure & chemistry of hair.

Basics of Hair:

The hair shaft is composed of three major parts: the cortex, medulla, & cuticle.

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Cortex:  Contains melanin and moisture.

Melanin is what determines hair color.
There are two main pigments:

- Eumelanin- black & brown pigments  
- Pheomelanin- red & yellow pigments that give your hair warm tones

Medulla: Innermost layer of hair shaft.

Cuticle: Protective, outer layer of hair shaft.  Made up of little scales that lay flat or are raised.



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Smooth vs Raised Cuticle:

  - Smooth/closed cuticles result in healthy hair since moisture and
  shine is locked in. 

  - Raised cuticles results from the use of chemical products.
  Hot temperatures will also raise the hair cuticle.



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pH of hair: 

  Healthy hair will have a pH between 4 and 5.5.
  Acidic products will promote closed cuticles while
  Alkaline products will promote open cuticles.




Hair porosity is the ability of your hair to absorb moisture.

You can perform a simple test to determine the porosity of your hair.  All you have to do is drop a clean hair strand into a glass of water and see where the strand is after a couple of minutes.

Porosity

Porosity Test

Moisture

Hair Characteristics

Hair Products

Low

Floats on top of water.

Resistant to absorbing moisture.

Hair is resistant to chemical services.  Hair does not absorb products.

Products that are more alkaline are recommended for this hair type.  They will open up the cuticles so that moisture can be absorbed.

Medium

Stays in the middle of glass.

Moisture can easily be absorbed and retained in hair.

Hair is healthy and shiny. 

Occasional use of hair treatments is recommended.

High

Sinks immediately.

Easily absorbs moisture but simultaneously releases it.

Hair tangles easily due to raised cuticles.  Hair feels dry and is easily damaged.

Since high porosity hair can lose moisture easily, leave-in conditioners and sealers are highly recommended.