The Different Types of Dye:
There are many different method used to colour hair. The choice of which method to use will depend on the desired shade and longevity of the colour. Examples of the results can be found in the Photo Gallery.
Temporary - lasts for between 1-3 washes
This type of hair colouring is purely cosmetic, involving no chemical reactions within the hair. Pigments are applied to the surface of the hair, without penetrating any further. These are easily removed by washing and can be used for experimenting without commitment. These dyes, although dependent on the colour of hair being applied to, can be very brightly coloured, even glittery.
Semi permanent - lasts for between 5 and 15 washes.
Usually made from vegetable dyes these colours are mainly designed to adhere tightly to the cuticle surface, and to a lesser extent penetrate beneath the hair cuticle. Although no peroxide is present and therefore no chemical reactions take place within the hair, pigments can be become trapped beneath the surface resulting in longer lasting colour. These gradually wash out, but are able to provide brighter, more vibrant colours than are possible with permanent dyes. The effect of semi permanent dyes can be greatly enhanced by pre bleaching which opens the cuticles allowing greater penetration, and providing a blank canvas. Often after only a few washes semi permanent dyes can fades, the surface pigments greatly reduced. By reapplying at this point before the colour is completely diminished the surface pigments can build up, intensifying the colour and greatly increasing its longevity.
Permanent – lasts indefinitely (although some colours may fade significantly), hair has to grow out, or be chemically treated to remove colour.
The first safe permanent hair dye was created in 1907 by French chemist Eugene Schueller, in his Paris flat. The main ingredient in his dye was paraphenylenediamine (left), which is common in current hair dye formulation. Schueller went on to found his own company L’Oreal, which is now a global leader in hair technology.
Permanent hair colouring products often combine bleaching and colouring agent. The bleaching agent decolourises the melanin and prepares the hair for colouring by expanding and opening the hair cuticles. Small dye molecules enter the hair cortex where they react, increase in size and become trapped. By reacting within the hair an irreversible chemical change occurs thus rendering the colour change permanent. The resulting shade of the hair depends upon the natural (or if previously dyed artificial) composition of coloured compounds within the hair so the same shade of hair dye may result in colour from person to person. Home dye kits often include a post colouring conditioner. This encourages the hair cuticles to shrink, close and realign, giving longer lasting colour and shiny hair.
The effect of permanent hair dye can last for as long as required, however as mention the colour can fade slightly over time. This is particularly noticeable with red dyes, due to the very small size of the red pigments which escape from the hair shaft quite easily.