Hair Chemistry

HAIR CHEMISTRY 101

Hair is made of up of protein which starts off in the hair follicle. As the hair cells mature, they fill up with a fibrous protein called keratin. These mature hair cells travel up the hair follicle and become dead material once they leaves their roots – the reason why it doesn’t hurt when you get a haircut. In other words, hair is dead material.

    • Hair is composed primarily of proteins (88%).
    • These proteins are of a hard type (keratin)
    • Comprised of many amino acids
      • Cysteine
      • Aspartic acid
      • Serine
      • Alanine
      • Glutamic acid
      • Proline
      • Threonine
      • Isoleucine
      • Glycine
      • Tyrosine
      • Leucine
      • Phenylalanine
      • Valine
      • Histidine
      • Arginine
      • Methionine
    • With cystine which gives hair much of its strength, being the most abundant
    • The amino acids are joined together by “peptide bonds” which are;
      –     Hydrogen bonds
      –     Cystine bonds
      –     Salt bonds
      –     Sugar bonds
    • These bonds are link together to form the hair structure;
      • The “alpha helix“ a coiled coil structure

THE HAIR CHEMICAL BONDS

THE HYDROGEN BOND

  • This bond is responsible for the ability of the hair to be stretched;
    • its elasticity and return back to its original shape.
  • The hydrogen bonds allow us to change the shape of the hair temporarily with the aid of water or heat
  • It is the most readily broken down and the most readily reformed.
  • It is responsible for approximately 35% of hair strength and close to ~ 100% of hair’s elasticity

THE SALT BOND

  • Similar to the hydrogen bond
  • It is also responsible for approximately 35% of the strength of the hair but 50% of the hair’s elasticity.

THE CYSTINE BOND

  • Also known as the disulfide bond, sulfur bond, or just S bond
    • Formed by cross-links between cystine residues (amino acids) of the main polypeptide chains.
    • The main amino acid of hair (sulfur)
      • Responsible for
        –    Hair’s toughness or abrasion resistance
        –    Holding the hair fibers together
        –    Hair type (genetic mark up)

THE CYSTINE; SULFUR BOND

  • This bond is largely resistant to the action of acids but the can be broken apart by alkali solutions
  • Which what enables us to permanently straighten or wave the hair.
  • Permanent relaxers (straighten naturally curly hair)
    –     Breaks the disulfide bonds causing the hair to loosen up for reshaping. (a reducer)
  • Perms – acid based hair relaxers
    –     curl or wave naturally straight hair
    –     instead of breaking up the disulfide bonds totally, it weakens the internal structures of the bonds. (an oxidizer)

THE SUGAR BOND

  • Gives the hair toughness but little strength (5%).
  • Contributes to hair moisture

THE CYSTINE BOND

  • Responsible for hair type (genetic mark up)
  • Hair is curly or straight;
    –     depending upon the number of disulfide bonds between hair proteins found in the hair shaft.
  • The greater the number of links
    –      the curlier the hair,
    –     and the fewer the number of links; the straighter the hair.

HAIR PRODUCTS’ PH

A pH’s of 3.0 to 3.5

  • Will not only close the cuticle but more importantly compact it. This:

1) Adds natural shine
2) Detangles
3) Adds elasticity
–     The lower the pH, the higher the positive charge.
–     This in turn brings hydrogen bonds from a beta state (weak) to and alpha state (strong).

Hydrogen bonds account for nearly 100% of the hair’s elasticity.
4) Locks in moisture and protein
–     A compacted cuticle will not allow evaporation or dissociation as much as an open cuticle.