Cosmetic Hair Dyes and Hair Coloring Techniques:

Hair coloring in a variety of colors and shades made by vegetable extracts and metal salts. Hair colors works due chemical reactions between the molecules in hair, pigments, as well as peroxide and ammonia, if they're present.

In 1909, the French chemist Eugene Schuller invented the first safe commercial hair color. Schuller used a chemical called paraphenylenediamine. Keratin is the main ingredient in hair.  

Keratin is the same protein found in our skin and fingernails. The natural color of hair depends on the ratio and quantities of two other proteins. Eumelanin is responsible for brown to black hair shades; phaeomelanin is responsible for ginger, and red haircolors. The absence of either type of melanin produces white or gray hair .

Melanins are biosynthesized in hair follicule by e serious of enzymatic reactions with amino acid tyrosine.

A hair cuticle is the outer layer of hair shaft. The hair cuticle must be opened before permanent color can be deposited into hair. Once the cuticle is open, dye reacts with the inner portion of the hair to deposit or remove the color. Most permanent haircolors use a two-step process which first removes the original haircolor and then deposits a new color. Except that a colorant is then bonded within the hair shaft. Ammonia is the alkaline chemical that opens the cuticle and allows the haircolor to penetrate the hair cortex. It also acts as a catalyst when the permanent haircolor comes together with the peroxide. Peroxide is used as either developer or oxidizing agent. The developer removes pre-existing color. Peroxide breaks chemical bonds in hair, releasing sulfur. 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 haircolor. The conditioners close the hair cuticle after coloring to seal in and protect the new color.

There are 4 different hair dying systems:

Temporary.. The pigments are use the particular size is bigger and only can cover hair shaft. They are not harmful. They only make a film on hair and they stays short time. If the metalic dyes are used in this type of products can blow out the package.

Semi Permanent hair dying is the one the dye are deposited into the hair in basic PH should be in between 8-9. There is no oxidative chemicals are used. In this case the azo dyes and aniline dyes can be used and known as harmful to health. Polymer dyes can use but need to  heat to deepen the color penetration.

Demi-Permanent; Analine dyes are used. %10  mild peroxide and basic chemicals used except ammonia. It allows dye molecules to penetrate into the cortex and deposit color inside the hair shaft. To increase the PH either MEA or AMP uses in the formulations. MEA is a pH adjuster that can release nitrosamines which cause cancer in animals and can cause severe eye irritation in humans.

Permanent:  At this technique phenylendiamine and hidrogen peroxide can be used. An alkaline reaction causes the cuticle to swell, allowing hydrogen peroxide and dye to enter.

• The hydrogen peroxide“oxidizes” (diffuses) the melanin, and “lifts” (lightens) the color.

• The hydrogen peroxide also causes the dye to “develop” and “deposit” color.

• A neutral or slightly acid after-rinse stops the alkaline reaction, allows the cuticle to close, and traps the color molecules inside. 

Semipermanent hair dyes consist of small moleculer alkali bases such as nitrobenzene, azo, antraquinone ( e.g., 2-amino-4-nitrophenol (yellow), 4’-hydroxy-2-nitrodiphenylamine(oranj) 1,4-diaminoanthraquinone (violet) 1,4,5,8- tetraaminoantroquionone (blue). When these dyes applied to the hair cuticle swels them and small sysnthetic pigments move between hair shaft and outher cuticle. Some of the pigments wash out with shampooing.  Some hair treatment products are designed to use action of metal ions with organic molecules. A solution contains Lead acetate after applied to the hair shaft the hair becomes brown-black color. The main reason for that is Lead has a reaction with Sulfur in cysteine amino acid of the hair protein keratin. So it truns to PbS lead sulphur gives this color. After repeated application the hair becomes more darker.


Ammonia-free hair colour :

Ammonia-free hair colour is a major trend in hair colour technology. In the past ammonia has been used in permanent hair colors to give better, more durable colors and allows for more significant color changes. Ammonia partially removes the natural colour from the hair.

 This method of depositing colouring the hair has been commonly reported to have side effects such as stinging the eyes and scalp, and of course there’s that distinctive odour…

Ammonia-free colours most often work by using an ammonia alternative called MEA. In this type of products uses intra-lipid ammonia-free technology. This new colour system has an advantage over other oil-based delivery systems as it doesn’t weight the hair with heavy oils, and leaves the hair in exceptional condition.

Previously it has been thought that ammonia-free hair colour systems were not able to produce the same lasting and permanent results as those containing ammonia, or the same lasting grey coverage. Developments in ammonia-free technology now mean uniform and lasting colour, with perfect coverage of up to 100 percent white hair with vibrant shades and lightening ability.

A novel "permanent" acid-type hair color  with dye-metal ion complex technology:

The advantages and disadvantages of oxidative permanent and acid-type semi-permanent hair colors are evident. It is well known that while the oxidative hair dyes  provides a longlasting "permanent" color, but also gives damage to the hair. With new developed technology with  acid dyes we can make longlasting permanent hair dyes. This  technology that can allow an acid dye and a metal ion to form a complex inside the hair similar to the oxidative hair color. It is well known that acid dye diffuses into the hair and creates an ionic bond with the positively charged amino acid residues of hair protein. However, the dye can be extracted easily from the hair by daily shampooing due to the weakness of the bond. In order to strengthen this bond and to prevent the extraction of the dye by shampooing, an aluminum chloride ion was chosen as the metal ion component to form the dye-metal complex. A proper composition of penetration enhancers, benzyl alcohol and ethyl alcohol, was required to allow acid dyes to interact with the aluminum chloride ion after each component penetrates deeply into the hair to form a complex inside the hair. To provide color brightness and a color longevity effect to hair color, glycolic acid was also selected due to the observation that a weak acid with a small molecular weight would enhance those effects.

Influence of urea on the coloring ability of a low-temperature coloring method of keratin fibers using polyethyleneimine:

Investigating at low temperature application with polyethyleneimide (PEI) when it applied to hair and dye with acid dyes shows that more coverage of the hair died.  The coloring and color fastness to shampooing of the hair pretreated with a PEI solution containing urea clearly improved compared with those pretreated with a PEI solution not containing urea.  

Oleth-5 Phosphate (and) Dioleyl Phosphate:

is a phosphate-ester that is able to deliver actives to the hair. This phosphate-based color enhancer is recommended for hair dyes and make faster coloring rate inside the hair cortex. This allows hair colour formulators to create hair dyes with more colour uptake, greater colour intensity and better colour washfastness. Furthermore, it is able to enhance the deposition of various cationic polymers. This product is recommended for permanent, semi-permanent and temporary hair colour.

 Silicones used in permanent and semi-permanent hair dyes:

Different kinds of silicones were incorporated directly into permanent and semi-permanent hair dyes. Hair treated with a silicone free control or the silicone modified hair dyes was tested for color and lightness change (fading) by washing the treated tresses several times and measuring the color change. The tests showed that dimethiconol/dimethicone mixtures can reduce the washout of hair colorant clearly and silicone resins like trimethylsiloxysilicate or propylphenylsilsesquioxane are able to decrease the color change occurred by UV radiation.

Natural Organic Hair Dyes:

This is the at latest trend on hair dye technology and highly demanded. In these formulations ammonia and PPD is not using but organic pigments, extracts and mineral salts are using. In fact mineral salts help to retain the color performance also.