Practical information on hair bleaching

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Hair Bleaching
Hair bleaching is a process used to lighten the normal hair color. The normal color of the fibers is due to the presence of melanin pigments which are naturally produced in the hair follicle by melanocyte cells. The melanin pigment is produced when the hair is in the growing or anagen phase.

As the hair fiber is produced from the root of the hair follicle, melanocyte cells produce and release melanin pigment. The pigment is taken up by the cells of the hair fiber and fixed into position as the hair keratinizes and hardens into a hair fiber. After the application of bleaching agents this normal melanin in the hair fiber is oxidized into a colorless compound.

The chemical solutions that are used for hair bleaching are oxidizing agents. Among them, the most effective oxidizing agent is hydrogen peroxide. When applied on hair, the colorless and odorless hydrogen peroxide releases oxygen. Oxygen then binds with the hair pigments causing a chemical reaction. This lightens the natural color of the melanin pigment.

Mechanism of bleach on hair
Bleaches act on the melanin pigments of hair. Hair generally contain two types of pigments known as phaeomelanin and eumelanin but the quantity of the pigments varies with the hair color. For example; dark black or dark brown hair contains more eumelanin while red hair contains more phaeomelanin.

Eumelanin is easily faded from the cortex layer of the hair fiber after the application of bleaching agents. But decolorising the phaeomelanin pigment is quite difficult and requires strong, effective bleaching. So bleaching of red hair is quite difficult when compared to dark black hair. When the dark black hair is bleached the color of the hair changes in the following sequence:

Black hair -Brown — Red-Orange—Yellow—Pale yellow—White

After the hair is strongly bleached it usually looks yellowish. It is due to the color of the keratin protein which becomes evident after the removal of hair pigments. The keratin protein is naturally yellow in color.

Various uses of hair bleaching
Bleaching is generally performed before the application of colors as with permanent coloring. Bleaching lightens the normal hair color so that when the dye is applied you can get the right effect of the color. It can also be used after the application of hair dyes in order to remove or lighten the tint of the hair.

Hair bleaching also helps to lift the cuticle scales slightly which makes the hair more porous. The porous hair therefore becomes more susceptible to tinting as the color is able to penetrate the cuticle layer and enter the hair cortex more easily.

Tips on hair bleaching
  • It is better for bleaching to be performed by experts rather than trying it on your own at home. Hair color experts will often use various modern equipment to speed up the bleaching process and minimize the potential damage to the hair fiber.
  • If you prefer to bleach at home, buy a well-known product. While buying bleaching products check for the toll-free consumer help number. You can get some help from this number if required during the application procedure.
  • Always perform a patch test for any allergy, before applying the desired hair bleach to your hair.
Harmful effect of bleaching in hair
Hair bleaching is facilitated by slightly raising the cuticle layer for improved penetration. This is a harmful process as it causes the hair to become more porous. Repeated bleaching also makes the hair lose its shine, luster and its strength. It leads to the formation of weathered hair and the hair looks dull with innumerable split ends.

The harmful effect of bleaching in hair becomes worse if the hair is back combed or combed when it is wet. So special care has to be taken of the bleached hair and hair that has undergone hair treatments like permanent waving, curling etc.

Applying bleaches prior or after tint application enhances the effects of the color provided it is done by experts and the hair is nourished by healthy hair care products like right shampoos and conditioners.

References:
John Gray, “Hair Care and Hair Care Products”, 2001, Clinics in Dermatology;19:227–236
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