Notes

- In the 1800s, chemists found a substance called as para-phenylenediamine (PPD) and discovered its use in the creation of a synthetic dye. At the same time, it was found that hydrogen peroxide was a gentler and safer chemical as compared to the other chemicals for hair bleaching. These two discoveries paved way for chemist Eugene Schueller, who created the first commercial chemical hair dye, which he called as "Aureole." This product was later known as "L'Oreal."
Hair bleach contains ammonia and peroxide. Ammonia is a colorless, pungent, suffocating, high-water-soluble, gaseous compound (dictionary.com) usually used in fertilizers and disinfectants. Peroxide, also known as hydrogen peroxide, is a liquid that is simply used as a bleaching agent. (dictionary.com) The ammonia works as a catalyst that activates the peroxide (bleaching agent). Once the bleach is applied to the hair, the bleach oxidizes with the melanin molecules found in hair causing it to become lighter. Hair melanin is what determines our hair color, hence if you have a lot of melanin, your hair is dark, if you have little melanin, your hair color is light.




Hair dye works similarly to bleach, just not as strong. It also contains ammonia and hydrogen peroxide. The dye breaks into the open cuticles of one's hair. The reaction opens and expands hair molecules to the point that they cannot be washed out, hence making it permanent. There are temporary dyes as well which is less harmful to hair.