Coloring Hair
Color Agents
Coloring agents for hair are of four main types: temporary hair color, natural colorings, semi-permanent dyes and permanent dyes.
Temporary hair color
The dyes used as temporary hair coloring agents were originally developed for use in textile industry. They are acidic dyes that are deposited on the outside of the hair, so they do not penetrate the hair shaft. They affect the way in which the cuticle reflects light, and they tend to make the hair look flat. They are easily shampooed off the hair, so they last through only a few washes. They are available as rinses, gels, mousses and sprays.
Unlike some of the permanent hair dyes, temporary hair colors carry very little risk of irritant or allergic dermatitis when they are used.
Natural colorings
Natural colors have been used on hair since ancient times. Most of them are made from plants. Henna is by far the best known. It is widely used to this day to redden hair, especially dark hair, and the color produced lasts through several shampoos. But its concentration is difficult to control, and hence results can be unpredictable. It has been reported to cause asthma and allergies in some people, and people who suffer from these ailments should be wary of using it.
Henna should not be used on gray hair, as it turns it orange!
Semi-permanent dyes
Special hair dye preparations are made for coloring gray hair. They can be used to add highlights too. They do not contain a single dye but mixtures of red, yellow, blue, and orange dyes in various proportions. The dyes have small molecules, which means they can pass through the cuticle into the cortex easily, and without damaging the scales of the cuticle. Since they can enter the hair shaft easily, they can also be washed out relatively easily.
They can last for 6-12 weeks, and tend to fade or lighten over this time. The red dyes seem to be the quickest to leak out of the hair, and as a result the hair can look drab after a few washes.
Semi-permanent dye preparations do not contain bleaches, and are therefore safe to use. They can be used at home. Without bleach, however, they cannot color hair lighter than its natural shade.
Lightening hair
Hair is made lighter by changing part or all of the melanin pigment in the cortex into a colorless substance. The melanin is not washed out of the hair - it is changed chemically, and the change cannot be reversed.
The chemical solutions used are called bleaches. They contain oxidising agents, like those in neutralising lotions for perms, in alkaline solution. The bleach most commonly used is hydrogen peroxide. Hydrogen peroxide can be used alone to lighten dark hair, or together with a coloring agent (a tint).
As you will recall, red and blond hair contains more phaeomelanin than eumelanin. On the other hand, dark hair - black or dark brown -contains more eumelanin than phaeomelanin. Of the two kinds of melanin in hair, eumelanin is the more easily removed from the cortex by bleaches. This is why bleached dark hair tends to look reddish: the
eumelanin has been decolorised, and what is left is mostly phaeomelanin. Further bleaching removes the phaeomelanin too. This is also why red hair is harder to bleach than dark hair.
Strongly bleached hair looks yellowish, because keratin itself is naturally pale yellow. This natural color is the reason why an elderly person's white hair looks slightly yellow at the roots, as mentioned in Chapter 1. It also explains why repeatedly bleached hair looks the color of nicotine-stained skin. It needs to be tinted as well as bleached if it is to be turned white or a 'platinum' blond.
The stages of lightening hair
The color of hair changes as it is lightened, as more and more eumelanin and then phaeomelanin is removed step by step.
Suppose that a black-haired client decides she would like to be a platinum blonde. To make this change at a single session, her stylist would have to use the most powerful bleaching chemicals available. They would certainly damage her hair to a marked extent. It would be less damaging to carry out the process in several stages - up to a dozen, perhaps. During that time her hair would change from black to red, and then lighten gradually from red to orange, orange to yellow, and finally from yellow to white. Some of the stages might well have to be repeated.
The stylist might decide that a three-step or five-step programme would be possible, changing first from black to red, then from red to yellow, and finally to white. What has to be considered before any final decision is taken is how to keep damage to the cuticle to a minimum, and above all what will be the final effect of the programme on the quality of the hair.
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HAIR FACTS |
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Problems in the bleaching process
Raising the scales of the cuticle for penetration by the bleach is in itself a potentially risky process. Repeated bleaching can leave permanently raised scales and upset the moisture content. It increases the porosity of the hair, and this makes further bleaching more difficult: very porous hair bleaches badly, with uneven shading. Repeated bleaching leaves weak, brittle hairs which have little shine or lustre, and which weather rapidly. Additional cosmetic procedures such as perming simply make things worse.
Bleaching is not the only effect of treating hair with oxidising agents. Side-reactions often happen, such as breakage of some of the strong disulphide bonds of the hair. Re-bleaching, which means treating the whole length of the hair rather than just the roots, is certain to break more of these.
The cuticle is especially easily weakened in this way. As a result it becomes extremely easy to strip it away from the cortex, even during routine hair care. Wet combing, for instance, becomes more difficult and causes additional damage. Backcombing is especially damaging because it can removes large amounts of cuticle with a single sweep of the comb.
Bleached hair, being porous, swells more readily when it is wet, and its wet strength is reduced still further. Eventually the hair protein may become so weakened that it separates and the hair breaks.
Permanent hair color
This is the kind of hair coloring that is used most commonly throughout the world. It is the type that has to be used if a
complete change of hair color is required. Highlighting or coloring just part of the hair using a permanent color is possible, however.
When changing hair color, it is wise not to make a permanent change of color all at once, especially if the new color will be very different from the old. It is sensible to try a temporary color first: this can be washed out straight away if the effect is disappointing. The next step would be to use a semi-permanent dye. Only if this is successful would it be advisable to move to permanent coloring, and that is something that should ideally be done by a professional.
The two-step coloring process starts by stripping the hair of all the melanin that gives it its natural color. Hydrogen peroxide in 30-40% solution is used. This is one of the harshest of all procedures used on hair, because the bleach destroys hair keratin. The hair can look lifeless when bleaching is complete, and another chemical process follows, using a new color.
A more typical procedure uses a gentler bleach (20% hydrogen peroxide solution) together with a dye and an alkaline soap or synthetic cleansing agent.
Allergies have been reported after the use of permanent colors, especially preparations containing the chemical ammonium persulphate. It is always wise to carry out a patch test on a client's skin before using any coloring process, in case there is any possibility of irritating, unsightly or painful allergy following the treatment. No coloring agent should ever be used on a client who is showing clear signs of dermatitis.
When shampooing after hair coloring, or indeed after any chemical processing of hair, use a shampoo with an acid balance as this will help the cuticle scales to close up and lie smooth again.
With regular professional re-tinting, using the same product, the hair can be kept the same color for as long as required.