HAIR COLOURANTS

 

ABOUT AUTHOR:
Vinay Kumar Singh

General Manager-Technical,
Mikasa Cosmetics Limited,
Ahmedabad, Gujarat
vinay.s@mikasacosmetics.com

The colouring of hair is one of the most important acts of adornment among those made by men and women since the origin of man. The reasons for getting the hair coloured have been to change the natural colour; to colour the white hair which begin to appear with age or to change the colour of the hair temporarily on a particular occasion.

Adding color to your hair always breaks the mundaneness while adding to the personality. However, you cannot just select any shade at random and sport the look, you may end up looking weird. On one hand where the choice of right color can enhance your appearance, a bad decision can ruin your entire look. Choosing the right color for your hair requires a lot of analysis as we are group of people with varied colored skin tones and face shapes. What hair color suits people from other countries may not suit us Indians. Highlights are the latest fashion trend.

“Complimentary colours” are opposite each other on the colour wheel. Blue-orange, violet-yellow, etc. If you want to neutralize unwanted highlights, choose the complementary colour. For instance, red will cancel out an ash undertone, and an ashen colour neutralizes any red highlights in your hair.

Be sure to check if your hair colour is a “progressive dye”. Progressive dyes continually add more colour with each use. For instance, if you’re colouring blond hair black, your first use of a progressive hair colour may not give the result you expected. However, continued use will turn your hair jet black.

Time was when your hair colour choices were blonde, red, brunette, and black, but those days are long gone!

Each basic hair colour comes in a full array of choices from platinum blonde to jet-black. Moreover, the modern consumer must choose from non-traditional hair colours that range from hot violet to champagne colour.

Chocolate, almond, honey, caramel… these are not only flavours of ice-cream on a dessert menu, but they also represent the new, funky shades of hair colour that have entered the Indian market in the past few years.

However, the wrong hair colour choice can give you the blues and leave you red in the face!
The best part is that streaked hair and glossy rich coloured tresses, which used to be the fancy of the rich and famous has now moved to the masses. This is evident from the fact that the hair colour industry grew by more than five times in the last 10 years.

Now let us look into chemistry of Hair Colours.

HAIR COLOURING SYSTEMS
Modern systems of Hair Colouring may be divided into three categories in terms of the duration of the presence of colour on hair after application.

1. Temporary colouring:
These are fugitive colour which can be removed at the first shampooing.  These are basically colour rinses. These products have colours of a high molecular weight which are in effect deposited on the surface of hair without being able to penetrate into the cortex.

2. Semi-permanent Colouring:
These are colours which resist several shampooing (3 to 6) but whose fastness is poorer than that of permanent colours. The colours used are Direct Dyes of Low Molecular Weight having a good affinity for hair keratin and capacity to penetrate the cortex.

3.  Permanent Colouring:
These are Resistant to shampooing and other external factors such as brushing, friction, light etc. and provide effective permanent colouring.

In this system, uncoloured intermediates are used which then by a series of chemical reactions produce in site in the hair the desired colour.  The process is oxidation followed by coupling and further oxidation.

CHARACTERISTICS OF AN IDEAL HAIR COLOURANT
The ideal hair colourant should possess the following properties:

1.  It should be non-injurious to hair shaft but should colour the hair without impairing the natural texture and gloss.

2.  It should possess no primary irritant action and be free from sensitizing properties.

3.  It should produce no toxic effect when in contact with the skin.

4.  The colour of the dyed hair should be stable to air, sunlight, friction and sweat.

5.  It should not change colour, nor bleach out on the application of toilet preparations such as setting lotion, hair waving preparation, soap or shampoo etc.

6.  Colourants should be stable over time in the aqueous solutions and formulated products in forms in which they are sold and used.

7.  It should not produce different colouration on different parts of the same hair.

8.  It should have affinity for Hair Keratin and capacity to penetrate into the hair shaft.

THE PROCESS OF HAIR COLOURING:
Hair colourants provide a a range of commercial products capable of colouring the hair in various shades and tints, ranging from very light blonde to black, passing through a range of tones, like Golden Ash, Reddish, Mahogany, Violets, etc. The number of shades constituting such a range could be as high as sixty or more.

Commercial products are mixtures of several single dye stuff say three to ten. In fact, each particular colour is the overall results of this super position of individual colourants. The total quantity of all the dye stuffs used to obtain a shade is small and limited. It can range between 0.01 to 0.5% by weight of the tinting medium applied to the head. The time of contact of  the dyeing solution with the scalp and the hair is of the order of 5 to 40 minutes. The amount of dyeing solution applied to a female head varies between 15-100 ml. For temporary dyes the frequency of application could be once a week and for permanent dyes the frequency could be once a month. The colourants must be conceived and formulated so as to avoid to the maximum extent the staining of the scalp.

TEMPORARY HAIR DYES:
The dyestuffs used are generally basic dyes, acid dyes, disperse dyes, pigments or metallised dye belonging largely to the chemical classes:  AZO, ANTHRA QUINONE, TRIPHENYL METHANE, PHENAZINIC, XANTHENIC OR BENZOQUINONEIMINE.

Temporary hair colouring can be achieved by two principal types of products: Rinses and Coloured hair setting lotions. In Rinses the dye- stuff are used in the form of simple aqueous or hydro-alcoholic solutions where as  in coloured setting lotions dyestuffs are added to the setting lotion which contains polymers like PVP.

SEMI PERMANENT CLOURANTS
These dye contain dyes which are often indispensable in the formulation of the permanent colours. Certain of these dyes are capable of providing hair shades ranging from yellow to orange which are practically impossible to obtain with oxidation dyes.

The great majority of dyes belong to following chemical classes:

NITROPHENYLENEDIAMINE, NITRO AMINOPHENOL, AMINOANTHRAQUINONES

The general formula for first two dyes are: 

Semi-permanent colourants can be presented either in the form of foaming lotions or as anionic or cationic shampoos.

PERMANENT HAIR DYES
Permanent hair dyes are based almost exclusively on the use of oxidation dyes, the so called para dyes, which are substances that are colourless at the time of their application to the head (the precursors) and are transformed into a coloured material in situ on the hair as a consequence of chemical reactions set in motion by the execution of coloration.

The precursors can be classified into two categories:  The compounds called oxidation bases or primary intermediates and these called couplers or modifiers.

The chemical reactions in the formation of dyes are oxidation reactions and couplings or condensation effected at alkaline pH by the action of oxidising agent. Almost exclusively Hydrogen peroxide or one of its solid derivatives like Urea peroxide or Melamine peroxide.  The choice of Hydrogen peroxide is justified not only by its action on the precursors but also by its ability to promote the simultaneous decoloration of the hair to be tinted.  Thus in order to create colour by this process, it is necessary to have three types of reactive chemicals.

Base or primary intermediates
Couplers or Modifiers
Oxidizing agent (which almost always is Hydrogen peroxide)

Bases are aromatic compounds, almost exclusively benzene derivatives, substituted by at least two electron donor groups such as NH2 and/or OH, these being para or ortho to each other, this confers the property of easy oxidation.  The most important compounds of this class are p - phenylenediamine and p -aminophenol, o - aminophenol, to which one could add the p or o - dihydroxybenzenes.  Starting from these basic compounds and proceeding by various substitutions, or by drawing on other aromatic systems, there has been number of bases which could be used in oxidation dyes.

COUPLES OR MODIFIERS
These are aromatic compounds, almost exclusively benzene derivatives, substituted by the NH2 and OH groups as in bases but in meta position to each other. In this position couplers do not have the property of easy oxidation by H2O2. The most usual couplers are as follows:

                        m         -           phenylenediamine

           2,4  Resorcinol     -           diaminoanisole

                        m         -           chlororesorcinol

                        m         -           aminophenol

                        2          -           methylresorcinol

FORMATION OF COLOURS IN HAIR
Mechanism of oxidation dyeing depends on a number of parameters e.g. pH, presence of hair keratin, complexity of reaction mixtures, possible hydrolysis of intermediate products etc.

The general picture of formation of colours lies in a series of oxidation and coupling reactions in which one can schematically distinguish the three following stages:-

a) Formation of Quinoneimines:
This phase consists of the oxidation of the bases under the action of alkaline H2O2 with the formation of Quinonemonoimines from p and o - aminophenols and quinone di-imines from p and o - aminophenols and quinone di-imines from p and o - phenylene diamine.

b) Formation of Diphenylamines:
The quinone immonium cations formed in the first stage readily undergo Micheal - type conjugate - additions with the pseudo - carbions of the couplers, to give an N - substituted p - phenylene diamine, in other words, a differently substituted diphenylamine.  Nucleophilic compound structures capable of addition at the-NH of the quinone imines by attacking the Nitrogen atom not only include the meta-structure couplers but also the original para-bases not yet oxidized and which then function as couplers for their own imines.

c) Formation of Colour:
The previously formed transitory diphenylamines can be seen in their turn as new oxidation bases, in which one of the benzene rings is at least tri-substituted (in positions 1,2,4 or 1,2,5) by electron donor groups.  By virtue of this, they possess the same two reaction potentialities as the original para-base from which they derive, namely oxidizability and ability to couple and this to an enhanced degree.

Thus, either they go to be oxidized and transformed into the appropriate indoamines, indoanitines or indophenols - in fact into a first group of dyes or they act themselves as couplers and are involved in an attack on the quinoneimines from the original para-bases, which continue to be formed in the reaction medium, thus, leading to ‘double’ phenylamine.  These new compounds easily oxidized in their turn, give rise in their oxidized form to a new group of dyes with three benzene rings.

This process of addition of the initial quinoneimines on to the transitory aromatic forms of compounds which are more and more condensed, followed by further oxidation, can lead to still new dyes with more than three benzene rings.  Because these dyes have other reaction capabilities such as intramolecular cyclization or partial hydrolysis, they can partially change into azines or oxazines that is to yet more dyestuffs.

All these dyes and pigments, of which all the structures are not yet completely elucidated, make up third group of dyes formed in the hair.

It should thus be restated that hair colouring by the permanent dye process is the result of competition between; on the one hand, indoamine dyes and on the other hand, dyes originating in a cascade of condensations and oxidations far remote from the primary reactions.  Following colours are to be achieved with following couplers and p - phenylenediamines.

Coupler                                               Colour obtained

Resorcinol                                           Green / Brown

m - aminophenol                                Magenta / Brown

2,4 - diaminoanisole                          

and m - phenylenediamine                            Blue

1 - naphthol                                           Purple - Blue

BANDROWSKI BASES
These are Trimers of p - phenylenediamine, which at one time were thought to be a principal intermediate in the formation of hair dye.  These bases have toxicological properties. But it should be made clear that in hair-dyeing conditions i.e. in the presence of hair and in a process of oxidation of the order of 30-35 mins.
a) Bandrowski’s base is not formed to any appreciable extent during the process as the formation of this base is a slow process.
b) In the presence of the various couplers which accompany para in a hair dye mix and which are considerably more reactive towards quinoneimine than oxidized para itself, no Bandrowski base is ever formed in quantities detectable by analysis.

TOXICITY AND DANGERS OF PARA DYES
Some components of these dyes e.g. p - phenylenediamine, p - to Idylenediamine are known to be sensitizers capable of causing contact dermatitis, thus a prophetic patch test must be carried out before dyeing.  Many countries have specified limits to concentration of ingredients in the formulae.

FORMULATION OF PERMANENT HAIR DYES
Following are the main factors which have to be considered in developing suitable formulations:
1. The formulation base like solution, emulsion, gel, shampoo or powder.
2. The selection of the dye components i.e. the oxidation base, the coupling agent or the addition of a direct colourant.
3. The selection of an alkali, usually ammonia is used.
4. Antioxidants: Usually a Sulphite, Ammonium thioglycollate or ascorbic acid is used to prevent oxidation of the dye before the product is to be used.
5. The pack: Required to be attractive and convenient in use.

The most convenient medium for colouring the hair is a shampoo. The system consists of the dye precursors together with an ammonium oleate soap or other surfactant, to which is added at the time of use another solution of stabilized hydrogen peroxide contained in a separate vessel. This mixture is applied direct to the hair and left in contact for 20-40 mins. Afterwards the hair is rinsed with water and then washed again. By use of various other additives such as fatty alcohol sulphates, fatty acid dialkanolamides, nonionic or amphoteric surfactants, fatty alcohols amine oxides, fatty amines and catonic surfactants a whole range of emulsion can be formulated in order to produce the dyes in the forms of creams, gels, shampoo etc.

OTHER DYES FOR HAIR
There are certain class of materials which have been used as oxidation dyes under ambient conditions. These don’t require chemical oxidation e.g.  Aromatic Polyhydroxy Compounds like 1,2,4 - trihydroxybenzene.

VEGETABLE HAIR DYES
Of the vegetable hair dyes, only henna is of any real importance today.  It consists of dried powdered leaves of Lawsonia alba, Lawsonia spinosa and Lawsonia inemis, which are removed from the plants prior to flowering. Henna owes its hair-dyeing properties to the presence of 2 - hydroxy - 1, 4 - naphthaquinone often termed “Lawsone”. In dyeing hair with henna, a paste of the powdered henna and hot water, slightly acidified with Citric acid to other suitable acids to an optimum pH of about 5.5 is applied to the washed hair.  Henna, has the advantage that it is neither a primary irritant nor a sensitizer and possesses no local or systemic toxicity. The colour obtained is relatively stable and is deposited in the hair shaft. The disadvantages associated with henna are - It is messy to use, Range of colour produced is limited to reddish auburn shades, contact with the finger nails must be avoided as it is stained, Repeated use produces a somewhat hard auburn colour.  By addition of other substances to henna, shades other than auburn may be obtained e.g. a mixture of powdered indigo leaves and hence produces Blue- Black shades and such mixtures are known as “Henna Rengs”. Of the various species of chamomile only Anthemis nobilis.  (Roman Chamomile) andMatricaria Chamomile (German Chamomile) appear to be useful in tinting hair. The active agent in these flowers is 1,3,4 - trihydroxyflavone, known also as Apigenin. Either an aqueous extract or a paste of the ground flower heads may be used.

METALLIC HAIR DYES
In these dyes, compounds of lead are the most frequently used, compounds of silver, copper, iron, nickel and cobalt are sometimes employed and less frequently salts of bismuth. These are very less frequently used dyes as they produce dull metallic appearance of hair and renders hair brittle.

HAIR DYE REMOVERS
The removal of hair dyes is sometimes necessary either because of a mistake or because the user wishes to have a lighter shade. In case of metallic dyes, removal is dangerous, thus one has to let the hair grow. Oxidation dyes can be removed by treating the hair with reducing agents such as sodium hydrosuplhate, sodium formaldehyde sulphoxylate, usually at a concentration of 5%.

BLEACHING AND LIGHTENING
These are basically a composition which contains Hydrogen, peroxide or peracid like persulphate in a suitable form to bleach new hair growth.

Market of Hair colour in India:
Hair colours were traditionally aimed at the 15-45 age female segments but there was a growing population of 15-45 males which patronized the category in a big way, with men wanting to look smart and trendy too.

Till the early '90s, the popular hair colours were powder dyes (Godrej Powder Hair Dye) or oil-based liquids (Super Vasmol). However, in 1997, Ultra Doux launched its premium brand Excellence Creme, which introduced the concept of hair colour other than just the regular black and dark brown.

Earlier, the 'traditional' Indian women were not experimenting with hair care and hairstyling, preferring mainly shikakai powder and henna. All this changed with the steady improvement in purchasing power of women and the increasing exposure to global hair trends. The Indian woman was bored with black and dark brown hair, so were tempted with the influx of new shades.

India's overall hair colour market is estimated to be around Rs. 2,900 crore, as per the report published in July, 2015; of which creme segment is 35 per cent and powder segment is around 40-42 per cent. The number of consumers using powder hair dye is still very huge as powder hair dyes are much cheaper. Both global and local players are in the Indian market making competition tough. In India, hair colour penetration is about 30 per cent, while there is still room for more growth. The rural market in India is brand conscious as well as it looks for value for money products.

Expert beauty consultants predict that the trend in hair colours is moving away from dramatic colour and back towards more natural colours and highlighting techniques. Thus One Goes Back To NATURAL & ORIGINAL.

NOW YOU CAN ALSO PUBLISH YOUR ARTICLE ONLINE.

SUBMIT YOUR ARTICLE/PROJECT AT editor-in-chief@pharmatutor.org

Subscribe to Pharmatutor Alerts by Email

FIND OUT MORE ARTICLES AT OUR DATABASE


FIND MORE ARTICLES