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Why Hydrogen Peroxide is added to hair colour

In order for permanent hair colour to work, it needs oxygen.  The harder you want the colour to work, the more oxygen you need. 

Hydrogen peroxide is an acid substance, pH 3.5 and is composed of 2 Hydrogen atoms (H) and 2 Oxygen atoms (O).  When the oxidising substance in the colour formula (i.e. ammonia) comes into contact with the Hydrogen peroxide, it releases the Oxygen from the compound. 

Hydrogen peroxide carries out the following functions:

Hydrogen peroxide balances the pH of the cosmetic colour

How much Hydrogen peroxide you need (the mixing ratio), depends on the pH of the colour formula.  Very alkaline substances damage the disulphide bonds in the hair structure causing damage and breakage.  The pH of the normal Inebrya tints are 9.5.  In order to balance the pH of the combination a mixing ratio of 1:1.5 is recommended.  This will lower the pH of the tint to an acceptable level to protect the integrity of the hair.  The Inebrya Superlighteners have a pH of 12 – thus more hydrogen peroxide is needed (a mixing ratio of 1:2) in order to bring down the pH of the mixture to within acceptable levels.

Hydrogen peroxide lifts the natural melanin from the hair

Hydrogen peroxide is labeled using either a %, a volume, or both.  Both measures indicate the concentration of oxygen available from the hydrogen peroxide contained in the bottle.

The % indicates the % of the content of the bottle that is pure Hydrogen peroxide.  The balance is water.  The Vol indicates the volume of oxygen that is released for every ml of contents.  For example, 1 ml of 20 Vol (6%) Hydrogen peroxide will release 20 ml of Oxygen. 

The concentration of oxygen in the Hydrogen peroxide will determine how much natural melanin will be removed from the hair.  Most hair colors require at least 1.5% peroxide to develop pigments contained in the color formulation.  Any remaining value in the peroxide creates the lift. 

Thus, the higher the volume or percentage, the more natural melanin will be removed and the lighter the hair will become.  Using too high of a volume developer can result in unnecessary lightening and major damage to the hair.  Too low a volume, and you may not get as light as you want.

Please keep in mind that hydrogen peroxide removes natural melanin and will not remove cosmetic colour.

Hydrogen peroxide oxidizes the pigments responsible for coloring the hair

When the Hydrogen peroxide is mixed with the colour formula, the oxidizing substance i.e. triggers the release of the oxygen that causes the colour molecules to polymerize and oxidise, getting trapped within the hair structure, thereby changing the colour of the hair.