Before choosing which hair color you want to dye your hair to, it is important to know what type of dyes are out on the market and how they differ in terms of application and performance.
Hair dying systems are usually divided into two main categories: oxidative (use of hydrogen peroxide) or non oxidative. They are also categorized according to the color durability after the application on hair: temporary, semi-permanent, demi-permanent and permanent.
In this article we will look at the non oxidative hair dyes.
Temporary non oxidative hair dyes
Like the name suggests these hair dyes can easily be washed off usually after 1 shampoo. The molecules in these hair dyes are usually large and therefore they do not penetrate the hair fibers. Instead, they lie at the surface only. There is no ‘lifting’ (lightening of the hair color) or opening of the cuticles, and therefore no damage involved in this process.
These dyes are merely for a temporary finish, and can only provide a nuance to hair. If the hair is light (such as blond), the dyes can be seen better. The disadvantage is that these dyes need to be reapplied everyday and are not efficient to cover grey.
An example of their chemical structure is shown below.
Semi-permanent non oxidative hair dyes
These products do not use hydrogen peroxide (no oxidation occurs in the hair) and consist of preformed dyes. However, these dye mixtures can contain a low amount of monoethanol amine (MEA) to provide a high pH and promote the opening of the cuticles. Since the dyes here are usually smaller than temporary dyes, they can penetrate into the hair fiber. Many of these dyes are either cationic (positively charged and attracted to negative charge on hair) or basic (attracted to the hydrogen of the hair proteins). These properties make the dyes suitable candidates for short-term hair coloring.
Usually these dyes last between 6-8 shampoos and the damage inflicted is minimal. However, these dyes are not efficient to cover up grey effectively (only about 30% coverage). The products usually consist of a conditioning agent to be used at the end of the coloring process. These conditioners are usually at a low to neutral pH, and help close the cuticles to provide a smooth feel to the touch.
Examples of semi-permanent dyes: