The Science Behind Professional Hair Color In A Nutshell:

By Team Di Carlo

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The first, safe, commercial hair color was created in 1907 by French chemist Eugene Schueller, using the chemical paraphenylenediamine (PPD). Since then, hair coloring has become very popular, with over 75% of women coloring their hair today and a growing percentage of men following suit. So, how does hair color work? It is the result of a series of chemical reactions between the molecules in your hair, pigmentation, as well as hydrogen peroxide and ammonia, if present.

First things first; what is hair?

Hair is mainly keratin, the same protein found in skin and fingernails. Hair color is the pigmentation of the hair follicles and the natural color of hair depends on the ratio and quantities of two other proteins – eumelanin and pheomelanin. Generally, if more eumelanin is present, the color of the hair is darker; if less eumelanin is present, the hair is lighter. Therefore, eumelanin is responsible for brown to black hair shades while pheomelanin is responsible for golden blond, ginger, and red colors. Levels of melanin can vary over time causing a person’s hair color to change, and it is possible to have hair follicles of more than one color. The absence of either type of melanin produces white/gray hair. The following sections will discuss a variety of possible agents used to color hair synthetically.

Natural Colorants

People have been coloring their hair for thousands of years using plants and minerals. Some of these natural agents contain pigments (e.g., henna, black walnut shells) and others contain natural bleaching agents or cause reactions that change the color of hair (e.g., vinegar). Natural pigments generally work by coating the hair shaft with color. Some natural colorants last through several shampoos, but they are not necessarily safer or gentler than modern formulations. It is difficult to get consistent results using natural colorants, plus some people are allergic to the ingredients.

Temporary Hair Color

Temporary or semi-permanent hair colors may deposit acidic dyes onto the outside of the hair shaft or may consist of small pigment molecules that can slip inside the hair shaft, using a small amount of peroxide or none at all. In some cases, a collection of several colorant molecules enter the hair to form a larger complex inside the hair shaft. However, shampooing will eventually dislodge the temporary hair color. Furthermore, these products do not contain ammonia, meaning the hair shaft is not opened up during processing and the hair’s natural color is retained once the temporary hair color washes out.

How Lightening Works

Bleach is used to lighten hair. The bleach reacts with the melanin in hair, removing the color in an irreversible chemical reaction. The bleach oxidizes the melanin molecule. The melanin is still present, but the oxidized molecule is colorless. However, bleached hair tends to have a pale yellow tint. The yellow color is the natural color of keratin, the structural protein in hair. Moreover, bleach reacts more readily with the dark eumelanin pigment than it does with the pheomelanin pigment, therefore some gold or red residual color may remain after lightening. Hydrogen peroxide is one of the most common lightening agents. The peroxide is used in an alkaline solution, which opens the hair shaft to allow the peroxide to react with the melanin.

Permanent Hair Color

The outermost layer of the hair shaft – the cuticle – must be opened before permanent color can be deposited into the hair. Once the cuticle is open, the dye reacts with the inner portion of the hair – the cortex – to deposit or remove the color. Most permanent hair colors use a two-step process (usually occurring simultaneously) which first removes the original color of the hair and then deposits a new color. It is essentially the same process as lightning, except a colorant is then bonded within the hair shaft. Ammonia is the alkaline chemical that opens the cuticle and allows the hair color to penetrate the cortex of the hair. It also acts as a catalyst when the permanent hair color comes together with the hydrogen peroxide. Peroxide is used as the developer or oxidizing agent. The developer removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor of hair color. As the melanin is decolorized, a new permanent color is bonded to the cortex of the hair. Various types of alcohols and conditioners may also be present in hair color. The conditioners close the cuticle after coloring to seal in and protect the new color.

Remember, we are your one stop shop to everything color!

Team Di Carlo



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