Chemistry Of Hair Essay

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THE CHEMISTRY OF DYING AND BLEACHING HAIR AND HOW THE pH IS AFFECTED

What is hair?
Hair is made mainly out of keratin which is a protein also found in the skin and nails. The natural hair colour of a person is determined by the ratios and quantities of eumelanin, which is responsible for darker shades of hair, and phaeomelanin, which is responsible for blonde, ginger and red hair colours., present in the hair. The absence of either of these proteins causes hair to become white/grey. [1]

Cosmetic hair colouring
Hatural hair ‘dyes’ such as henna and mineral salts and even beetroot are still used but hair colouring is becoming a predominantly chemical endeavour that involves the chemical manipulation of the chemistry and colour of hair fibres through bleaching and dying.
Colouring hair is a well-defined, in depth study of how keratin interacts with dyes, oxidising agents and conditioners.[2]

Temporary hair colour
Temporary/semi-permanent hair dyes deposit dyes on the outside of the hair shaft or consist of small pigment molecules that enter the hair shaft through the use of little to no peroxide. The lack of ammonia means the hair shaft isn’t opened during the dying process so the hair retains its natural colour after the dye has been washed out.[1]

Permanent hair colour …show more content…

The dye reacts to the inner portion/cortex of the hair to deposit or remove colour. Ammonia opens the cuticle and allows the dye to penetrate the cortex. It also acts as a catalyst when permanent dye comes together with peroxide. Most permanent dyes involve a two-step process; the first removing the hair’s natural colour (lightening/ bleaching the hair), the second adds the new one (colourant is bonded to the hair shaft). Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odour of hair

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