Understanding Hair Texture

• Hair is made up of proteins created by long chains of amino acids containing hydrogen, sulfur, carbon and oxygen ions. These ions form chemical bonds that hold the hair strand together and determine the texture and curl pattern. Sulfur ions are attracted to each other and, as the sulfur ions draw together, this causes the hair shaft to bend creating a wave or curl pattern. A hair shaft with more sulfur ions, placed closer together, will have a tighter curl pattern. A hair shaft with fewer ions, spaced farther apart, will have a more relaxed pattern.
  
  There are three types of bonds in hair: hydrogen bonds, salt bonds and disulfide bonds. Salt and hydrogen bonds are the most prevalent and also the most flexible. Both salt and hydrogen bonds are easily affected by heat and moisture. Disulfide bonds are much stronger and can only be broken with a chemical agent.
  
  

Flat Iron Function

• A flat iron works by applying heat to a strand of dry hair, which loosens the hydrogen and salt bonds. When the connection is broken, the plates of the flat iron rearrange the hair shaft into a new, straight formation. As the hair cools it retains the new straight shape. The hair must be divided into small sections in order to allow even distribution of heat. If the sections are too big or thick, the outer strands will act as insulation, preventing the heat from penetrating to the interior strands. A curling iron produces a similar effect but, because the heat surface is curved, it reshapes the hair into a curl pattern. It is possible to use a curling iron as a flat iron simply by running the iron straight down the hair shaft instead of curling the hair around the iron. However, the big advantage of a flat iron is that both plates heat which allows for the even heating of both sides of the hair section and faster straightening.
  
  

Keeping Hair Straight

• Because hydrogen and salt bonds are so flexible, any changes made are only temporary. As soon as the hair encounters moisture, it reverts to its natural texture. Many stylists use product to either delay reversion or enhance the effects of the heat. People with thicker, coarser hair may use an oil-based product during straightening, which increases the effect of the heat and helps seal the hair cuticle against moisture. People with finer hair may use a, lighter, silicone-based product, after straightening, to seal the hair cuticle.