Hair Dyeing
Two types of melanin pigments, namely eumelanin and pheomelanin, in hair are responsible for the color of natural hair. The former creates brown and black color of hair and the latter creates red and blonde color of hair. In absence of any pigments would result in grey or white hair. There are three hair dyeing methods with different duration:
Temporary hair dyeing
Temporary hair dyeing is suitable for one-night party and occasion that you just want to try out a new color. The pigment consists of some large molecules which cannot penetrate the cuticle hair but only remains on the surface of it. Therefore, the hair dye can be removed by shampooing easily. It can often persist on dry or damaged hair as they enable migration of pigments into the interior of hair. This kind of hair dye has a wide range of color choice and usually does not contain ammonia.
Hair lightening
Bleaching is an oxidation reaction of hair melanin that causes it to lose color. Bleached hair usually is pale-yellow as it is the natural color of protein, keratin, in hair. Since bleach is more reactive to eumelanin, some red and yellow residuals may appear after the process.
Permanent hair dyeing
In permanent hair color, ammonia is used in order to open the cuticle layer of hair so that dyes can react with the inner part of hair, cortex, allowing the removal of original hair color and deposition of new pigments. The first part of permanent hair dyeing is basically the same as hair lightening. After the cuticle layer is opened, ammonia acts as a catalyst of the decolorization, bleaching process. The hair can then deposit a new permanent color. The hair dye usually contains some conditioners. They eventually seal in the cuticle and protect the new color.
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