How Haircolor Works

Melanin chart Ask Mags hair color
by Mags Kavanaugh-AskMags

There are two kinds of melanin found in the hair: eumelanin (the most common and responsible for hair shades from brown to black) and phaeomelanin (responsible for yellowish-blond, ginger, and red colors).
The absence of pigment produces white/gray hair. 

All human hair types at childhood contain the two types of melanin, Eumelanin, and Pheomelanin. There is no hair type with only one type of melanin. Dark hair has a higher percentage (99%) of the brown pigment, eumelanin, and a much lower percentage (about 1%) of pheomelanin. Blonde hair still has about 95% of eumelanin and about 5% of pheomelanin. Of course, dark hair has a much higher overall amount of melanin (eumelanin and pheomelanin) than blond hair. 

Let us look at some numerical examples without putting much emphasis on the numbers because they are strictly hypothetical: If we assume that a dark hair strand has 10,000 “molecules” of total melanin, then by the ratios above, 9900 “molecules” (99%) of these would be eumelanin and 100 “molecules” (1%) would be pheomelanin. In comparison, a blond hair strand of equal size may have only 100 “molecules” of total melanin. 

Of these, 95 “molecules” are eumelanin (95%) and 5 “molecules” are pheomelanin (5%). When both dark and blond hair types are bleached, most of the accessible eumelanin in the two types of hair would be broken down and discolored, and only very little of the pheomelanin would do so. The reason why pheomelanin is harder to bleach is that it has sulfur linkages (or ties) that make the molecule more tightly packed and inaccessible to the bleach. The end result is that dark hair lifts to a brassy undertone because of the significant amount of pheomelanin left behind (let’s say 90 molecules), while blonde hair reaches the palest yellow stage because only very few pheomelanin were there to start with, and they get even less after the bleach (Let’s say 3 or 4 molecules).


So the lesson to keep in mind is that all types of hair have both types of melanin, but the concentrations differ.

What are the ingredients in peroxide-
(also known as the developer or oxidizing agent) — This ingredient, in varying forms and strengths, helps initiate the color-forming process and creates longer-lasting color.

The larger the volume of the developer, the greater the amount of sulfur is removed from the hair. Loss of sulfur causes hair to harden and lose weight. This is why, for the majority of hair coloring, the developer is maintained at 30% volume or less for less damage to the hair.

Ammonia — This alkaline allows for lightening by acting as a catalyst when the permanent hair color comes together with the peroxide. Like all alkalines, ammonia tends to separate the cuticle and allow the hair color to penetrate the cortex of the hair. In addition, various types of alcohols, which can also dry the hair, are present in most hair colors.

Types of Haircolor:

Level 1, semi-permanent color — This product adds color without changing natural color dramatically. The hair color contains tiny color molecules that enter the hair’s cuticle, or outer layer, and go into your hair’s cortex. They don’t interact with your natural pigments. And since the molecules are small, they eventually exit the hair shaft after several shampoos, leaving the hair as it was before treatment. This level generally lasts for 6 to 12 shampoos, covers up to 50 percent gray, enhances your natural color, and leaves no roots. This hair coloring won’t lighten your hair color because it contains no ammonia or peroxide.
Level 2, demi-permanent color — This product level lasts longer, through 24 to 26 shampoos. In this process, pre-color molecules penetrate the cuticle and enter the cortex where they then partner to create medium-sized color molecules. Their larger size means they take longer to wash out. These products do not contain ammonia so the natural pigment can’t be lightened. However, it contains a small amount of peroxide, which allows for a subtle, but noticeable, color enhancement. It also blends and covers gray. (Both semi- and demi-permanent colors can become permanent on permed or already-colored hair!)
Level 3, permanent color — This is what you need for a more significant color change. In this level, both ammonia and peroxide are used. Tiny molecules enter all the way into the cortex, where they react and expand to a size that cannot be washed out. Your hair actually has to grow out over time. This product acts to lighten the hair’s natural pigment to form a new base and then to add a new permanent color. The end result is a combination of your natural hair pigment and the new shade you chose. That means the color may appear different on you than on someone else using the same color. Regular touch-ups of 4 to 6 weeks are generally needed to eliminate new growth / roots — hair with your natural color growing at half an inch per month from your scalp.
Permanent Hair Color
The outer layer of the hair shaft, its 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’s essentially the same process as lightening, except a colorant is then bonded within the hair shaft.

The developer removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur, which accounts for the characteristic odor of haircolor. As the melanin is decolorized, a new permanent color is bonded to the hair cortex. 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.
Oxidation has only a minor role in opening up the cuticle. It is rather the alkaline base (in the form of ammonia or monoethanolamine) that causes swelling and loosening of the cuticle. Oxidation works progressively on melanin to bleach the color and causes irreversible changes in the melanin molecule and also to oxidize the dyes.

Dye intermediates undergo oxidation by the peroxide to form larger colored dye molecules. Dye intermediates by themselves are colorless. When a primary dye intermediate is oxidized, it loses hydrogen atoms and becomes activated so that it attacks a second dye intermediate in the form of a coupler or even another primary and binds to it covalently (strong bonding). This may be repeated more than once and the resulting molecule grows larger.
The effect of each oxidative dye is based on the following components: an alkalising agent – usually ammonia – and oxidation coloring agents. The alkaline agent has the effect of opening the outer hair layer so that coloring and oxidizing agents can penetrate into the hair shaft more easily.

The starting materials for developing the new color are called color precursors which are very small, colorless molecules that only develop their own color nuance once inside the hair. The oxidising agent – usually hydrogen peroxide – is mixed with the color precursors prior to application. The oxygen is released by the reaction between the alkaline agent and the oxidizing product. It triggers the actual color-changing reaction. Large, colored molecules are formed within the hair’s cortex which are resistant to being washed out of the hair. Simultaneously, the oxygen released will lighten the natural melanin pigment in the hair so that the new color can be seen, effectively replacing the hair’s natural color

Bleach is used to lighten the 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. 

Also, bleach reacts more readily with the dark eumelanin pigment than with the phaeomelanin, so 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.

How do permanent oxidation hair colorants work?
Suffice to know that for a chemical reaction to take place, the products of a chemical reaction must achieve a lower energy level (or are more at ease) than the starting reactants which are (tense or edgy). It is like trying to push a rock downhill but before you are able to get it to the edge of the hill (where it can roll down on its own), it has to climb a small mound of dirt. In doing so you have to give it a push and spend some energy. 

In hair color, the push over the small mound of dirt that your rock has to overcome (or the energy to get your primary intermediate activated) is provided by the oxidizer removing hydrogen atoms from the primary intermediate and making it chemically active (grouchy ready to bite). Keep in mind, however, that some of the most useful interactions between hydrogen and oxygen are not covalent but rather weaker interactions known as hydrogen bonds which give water its fluid nature and vital role in life.

As far as the types of melanin, eumelanin and pheomelanin, both start out very similar during their synthesis in the cell. They are both polymers (chains) based on the amino acid tyrosine. Tyrosine is changed through the action of the enzyme “tyrosinase” to a new molecule called dopa, which is then changed by the same enzyme to dopaquinone (Albinos in general lack the enzyme tyrosinase and their cells cannot make melanin). At this point, eumelanin and pheomelanin go in different directions. Eumelanin chains continue growing by adding derivatives of tyrosine, while pheomelanin add derivatives of both tyrosine and the amine acid cysteine which contains sulfur. 

These cysteine derivatives form cross-links or bridges among themselves which cause pheomelanin to be more tightly packed and resistant to bleach. The switch in the cell to synthesize either type of melanin (by adding tyrosine or adding cysteine) is related to genetic factors. 

Both types of melanins grow to form large granules of melanin chains wrapped around protein molecules. The chemical structure of both types is quite complex, and both have what is referred to as a highly conjugated double bond structure which results in the dark color of the pigment and allows the molecule to absorb UV light and offer protection against harmful radiation. 

When melanin is oxidized, the conjugated double-bond structure starts to break up and the melanin gradually loses color and becomes “bleached”. It is not eliminated from the hair but remains in the hair in its colorless “bleached” form.
Ammonia is a chemical agent that provides alkalinity and raises the pH of hair colorants. It swells the hair and allows for more penetration of dye inside the hair shaft to achieve deeper and more permanent hair color. It also helps the action of peroxide in lightening melanin and natural hair color. 

It is a very small molecule, which evaporates rapidly (hence the strong odor) and rinses out quickly from the hair. Hair coloring products labeled as “Ammonia-Free” utilize other chemical agents to provide alkalinity, and it is important to remember that “ammonia-free” does not mean “alkalinity-free”.

These other chemical agents are close relatives of ammonia, and include monoethanolamine (MEA) or aminomethyl propanol (AMP) which are larger than ammonia, do not swell the hair as well, and therefore do not allow as many dyes to diffuse deep into the hair. Hence the less than ideal results you observed with these products. They are less volatile (they do not evaporate as rapidly and therefore they do not smell as strongly), but they may take longer to wash out of the hair than ammonia By most scientific evidence available today, ammonia presents no serious health risks to hairdressers when used according to instructions and under normal salon conditions (which include some form of ventilation and controlled salon temperature).
Because of the relatively short track-record of MEA and AMP in hair coloring products, it is not possible to judge their long-term safety. Ammonia levels in hair color vary not only among different manufacturers’ lines, but also within the same manufacturer’s line. In general, deposit shades require as little as 4% of the ammonia solution, while the high-lift shades of permanent hair color may go well over 10%. On the other hand, demi-permanent (or deposit-only) color lines use little or no ammonia (or other alkalizing agents) at all. But their permanency is not as good as their alkaline counterparts.

Leave a Reply