hair_dyeing,perming,straightening

Sources: Walker, Better Hair Through Chemistry, Dawson, Milady

    "Hair is easier to alter than any other physical feature of your body"(Dawson). Modern chemistry has made it possible to change your hair color for a day or for as long as it takes to grow out. There are many different kinds of dye, which can suit anyone.

    Temporary dyes were invented in the 1930's, and are perfect for those who don't want the commitment of a perminent dye. They form a colored film over each hair and gradually wash off in the shower with the use of shampoo.

    Semipermanents came around in 1961. They contain alkali which swells and softens the cells in the cuticle. The colored molecules are tiny enough to get between the swollen cells and are able to get inside the hair. Eventually, however, it will still wash out. Just like natural hair, semipermanent dye contains a mixture of synthetic pigments to make a variety of different hair colors. For example, a burgundy hair dye has a mixture of red and blue pigments, and the smaller pigments, the red pigments, are able to get further into the hair cuticle than the bigger, blue pigments. So eventually, the blue pigments will be gone, while the red pigments remain. This causes the hair dye to fade and causes the tone of the hair to change with every washing.

    For the most adventurous there is bleaching and permanent dyes. These two are often used together. The bleaching solution contains alkali to soften the cuticle and oxygen is released through the use of hydrogen peroxide. The oxygen penetrates and reacts with the natural pigments of the cortex and breaks them down. This usually takes about an hour. After bleaching, another color is put in. The dyes start out as colorless molecules which are small enough to get into the cells of the cuticles and the hair. They react with the hydrogen peroxide to become colored molecules, and also form clusters which become too large to wash out of the hair. This leaves the hair permanently colored.

    If the procedure doesn't turn out the way you expected, there are steps you can take to somewhat get rid of the dye. A color stripper or reducer reverses the action of the hydrogen peroxide and breaks the giant clusters into tiny molecules that are able to be washed away. This works to get rid of the added color, but does not return the hair to its natural shade because some of the natural pigments in your hair were being destroyed while the oxygen from the hydrogen peroxide was making the clusters. This process leaves the cuticle damaged in the sense that the hair is extremely porous.

Perming and Straightening

    Curling hair messes with chemical bonds. No matter what you use, whether it be water and styling gel or perming, it destroys the bonds of the protein fibers of the cortex that keep it stuck together. A hydrogen bond is one of the chemical bonds, and it is a weak bond created when a hydrogen atom connected to a protein is attracted to an oxygen atom connected to another protein.

    Hydrogen and oxygen are what make up water. When hair gets wet, the water molecules seep in between the cortex and the proteins and join the hydrogen bonds and causes hair to swell up. However, in wet hair, one protein molecule doesn't join directly with another. The protein is stuck to a water molecule, which is stuck to another water molecule which is stuck to another protein. This type of bond is weaker than having the two proteins joined directly. That is why wet hair is easier to break than dry hair.

    This is also the reason that hair curls when it is wet. Setting wet hair in curlers or pulling it straight and letting it dry like this forces the hydrogen bonds to reform in this position. But when hair gets wet again, the bonds will weaken and return to the way they were before. This is why blow drying hair at home only lasts while hair is dry.

    Permanent changes are possible through other procedures. Perming causes the hydrogen bonds to break and also breaks the disulfide bonds which hold proteins together. A disulfide bond is the bond between sulfur atoms. The chemicals in the perm are what make the disulfide bonds disentegrate. Then the hair is reshaped and more chemicals are added to rebuild the disulfide bonds. This holds hair into its new shape, even in water, because disulfide bonds withstand water.

    However, usually 10 percent of the disulfide bonds broken while perming don't reform. This causes the proteins to be weaker and easier to break, and causes split ends.