Changes her hairstyle quite frequently. One month, she is rebonding her hair. The next, she is perming it. I told her that this damages her hair, but she doesn't listen. Actually, what is rebonding?
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Hair is made out of a protein called keratin. Keratin is also present in your nails. In hair, the keratin molecules are in straight bundles. These bundles are held together tightly by disulphide bonds. (Di = two, sulphide = containing the sulphur element).
These bonds are made from cysteine, an amino acid. The cysteine of one keratin molecule makes a disulphide bond with the cysteine of another keratin molecule next to it.
The bonds make your hair strong.
The more disulphide bonds you have you in your hair, the straighter your hair is.
Rebonding uses a salt called ammonium thioglycolate. It is the same salt that is used in perming your hair to make it curly.
Ammonium thioglycolate contains a thiol group (-SH) that can break disulphide bonds through a chemical process.
Once the disulphide bond is broken, the keratin bundles that are connected in your hair come apart. Your hair is definitely weakened.
During the rebonding process, the hairdresser will wash your hair, then apply this salt on it for a short while. The salt will work its process and loosen your hair.
Then, once the disulphide bonds are broken, your hair is pressed together with hot irons to straighten it. After it is straightened, your hair needs to be strengthened so that the hairstyle (in this case, straightening) becomes permanent.