Hair Biology & Bonds
Your hair is composed of keratin, a strong fibrous protein, and is built from cells similar to those of your skin. The average number of hairs on the human scalp is 120,000, although blondes tend to have more and redheads less. Hair is a remarkable fibre.
A healthy hair can stretch up to 30% of its length, can absorb its weight in water and swell up to 20% of its diameter. A single scalp hair can hold a weight of 100g and an average head of hair twisted together can support 23 tons. However, this is only if your hair is in good condition!
DISULPHIDE AND HYDROGEN BONDS
‘Disulphide bonds are one of the strongest naturally-occurring bonds in nature.’ The protein structures of the hair shaft are held together by chemical bonds called disulphide and hydrogen bonds.
While the curliness (or straightness) of your hair depends on the shape of the follicle, it’s the disulphide bonds that keep the hair in the shape it was formed, and they can only be altered by perming or relaxing.
Disulphide bonds also give your hair its elasticity and strength. Hydrogen bonds, on the other hand, are easily broken by the application of water and can be temporarily reset with heat until they become wet again (either from washing or humidity).