Hair- The Basics:
Hair is incredibly strong. Each hair can withstand the strain of 100 grams, meaning that an average head of 120,000 hairs could cope with 12 tons, if the scalp were strong enough!
Hair is composed primarily of proteins (88%). These proteins are of a hard fibrous type known as keratin, a protein which consists of polypeptide chains. The outer layer of the hair shaft, the cuticle, consists of many microscopic scales which when aligned gives the appearance of shiny hair. When hair is damaged (chemically or thermally) these scales lose their alignment and scatter the light reflected from within the shaft and off their surface, giving it a dull appearance. Within the cuticle is the cortex which determines the thickness, elasticity and strength of the hair. It is also responsible for housing the hairs natural colour pigments. Colour pigments found the cortical layer are in the form of minute melanin granules which are stored in tiny sacks call alveolus
Left: The hair shaftRight: The cuticle
The natural colour of your hair depends on the ratio and quantities of two proteins, which make up only 1% of the hair structure, called eumealnin and phaeomalanine. Eumalinin monomers make the hair brown to black shades while the phaomelanine is responsible for the blonde to red colours.
You can have one or both melanin pigment types and the ratio and concentration of each determines the shade of your hair colour. The absence of both melanin pigments results in white/grey hair
When light hits your hair it is able to pass through the transparent surface and is reflected off the melanin pigment, and/or dye particles within. The colour of your hair is determined by this reflection of light, as discussed in Colour –the basics.