Oxidation dye is a type that is commonly used as a base in permanent hair coloring. The oxidation intermediates are combined with an oxidant in an alkaline substrate to produce the desired hair color. This type of dye is popularly used in both salon and home coloring kits.
Used in permanent hair coloring, oxidation dye can produce a wide range of colors, from shades that mimic natural hair to the vibrant shades used in fashion colors. Oxidation dye is also good at covering grey hair. It provides a long-lasting result that fades slowly.
In order to use oxidation dyes in permanent hair coloring, they must be mixed with other chemicals. Two types of oxidation dye intermediates must be used. First is the primary intermediate. This dye does not have any color itself but undergoes a chemical reaction with a coupler and an oxidator to produce color. An example of a primary intermediate is 2,5-diaminotoulene, which is commonly used in black and brown dyes.
The coupler is the secondary intermediate. This component is already a colored dye and reacts with the primary intermediate to produce the desired shade. An example of a secondary intermediate is 2-nitro-p-phenlyenedramine. In order to become a complete dye and penetrate the hair, these two intermediates must be mixed with an oxidant.
A common oxidant in hair dye is hydrogen peroxide. Also called the developer, this component is usually present in hair dyes in liquid or cream form, with a concentration of approximately six percent. The hydrogen peroxide oxidizes the primary intermediate, causing it to react with the coupler. An alkali environment must also be present for the chemical reaction to take place. In permanent hair dyes, this is commonly ammonia.
To dye hair with oxidation dye, the ammonia and dye intermediates are usually premixed and packaged together. This mixture is then combined with the hydrogen peroxide solution immediately prior to application on the hair. Once applied, the ammonia causes the shaft of the hair to swell and the scales on the shaft to lift, allowing the dye intermediates to penetrate the hair.
After a short time, the primary dye oxidizes due to the hydrogen peroxide and reacts with the secondary intermediate. This reaction is visible as the hair dye cream or gel turns from a light color to a much darker one. The dyes must be left on the hair for a sufficient time to complete their reaction and produce a final color. Darker shades are obtained by using higher concentrations of intermediates.
Other dyes can be added to the oxidation dye to adjust the tone and vibrancy of color. For example, 4-amino-2-hydroxytoulene produces redder shades. Permanent dyes can cause damage to hair and skin, so it is important to first perform a patch test to determine sensitivity. The long-term effects of oxidation dyes are not well known; however, there are possible links to different forms of cancer.