A permanent hair colour works by depositing small artificial pigment molecules inside the hair.
If you think of hair as a swimming pool, imagine those artificial pigment molecules as hundreds of marbles. All permanent hair colour requires hydrogen peroxide to create a permanent result.
Peroxide causes something called ‘oxidation’ meaning the hydrogen peroxide ‘oxidises’ when the air hits it. This causes the artificial hair molecules (marbles) to expand (to the size of colourful footballs) and become trapped inside the hair (swimming pool).
Because those colour molecules have expanded they simply cannot be washed from the hair – no matter how hard you try – they are trapped and permanent. Colour UndoTM works by reversing the colour process. When mixed and applied to the hair, parts 1 and 2 of Colour UndoTM are able to shrink those big (football) artificial hair colour molecules back to their original (marble) size, enabling them to be rinsed away.
Colour UndoTM shrinks the artificial colour molecules and washes them from the hair, revealing the lightest, previous shade. This shade may be lighter than the natural colour, as bleach and ammonia from previous colour treatments may have lightened the natural pigment.