prevents running or dripping.
They are also used directly on the scalp. Their pH is about the
same as that of the oil lighteners.
Activators can be added to oil or cream lighteners to boost their strength. These activators
increase the pH of a lightener toward the alkaline side, thus increasing the speed of the oxida-
tion process. The pH is increased by chemicals called alkali salts and persulfates. Since activa-
tors can double the strength of hydrogen peroxide, no higher than 20 volume is recommended
when mixing for an on-the-scalp application.
2.
Off-the-scalp lighteners
(powder bleaches) contain alkaline salts and a strong
oxidizing agent that, when mixed with peroxide, become a strong lightening product.
These lighteners are much stronger than the oil or cream lighteners and lighten the hair
faster.
Because they have no added oils or cream, they can irritate the scalp causing burns and
blisters. For this reason they are usually used for off-the-scalp lightening procedures such as
highlighting.
Conditioning agents provide some protection to the scalp and the hair, however. Some off-the
scalp bleach powders have protein conditioning agents that help prevent chemical damage to the
hair during the lightening process. This type of powder bleach has a distinct advantage over ones
that do not contain conditioning agents. During the bleaching process, the conditioner can
protect the hair's internal protein structure and the surface of each hair shaft. The pH of powder
lighteners when applied to the hair is about 10.3.
Developers
Hydrogen peroxide (H
2
0
2
) is the most common developer or oxidizing agent used in hair
coloring and in hair lightening. It is mixed in various proportions and various strengths.
The strength most often used is a 20 volume solution.
Volumes refer to the amount of oxygen
gas that would be removed from a peroxide solution if
the molecule was broken into its compo-
nents, water and oxygen. Hydrogen peroxide is also called a developer or oxidizing agent
because permanent colors require peroxide to develop their color molecules. Peroxide comes in
different forms such as clear, cloudy, creamy and gels. Its pH is between 2.5 and 4.5.
In hair lightening, ammonia or other alkalis are used to activate or raise the peroxide's pH, therefore
making it more alkaline. Once activated by the higher pH substance, the peroxide can then act as an
oxidizer and lift or subtract hair color.
A hydrometer is used to measure the strength (volume) of hydrogen peroxide.
A hydrometer
indicates the potency (strength) of hydrogen peroxide and allows you to dilute higher strength liquid
peroxide to lower volumes. A hydrometer is also beneficial if there is a question about whether
hydrogen peroxide that has been stored over a long period of time is still potent. Manufacturer rec-
comendations will indicate
shelf life (usually 3 years) of hydrogen peroxide and instruct that
it be stored in a cool, dry place.
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CHEMISTRY
