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Nowadays many people, both men and women, color their hair for
a number of reasons, such as fashion, or for a change of image,
or most commonly simply to cover grey hair. There is an innumerable
amount of hair coloring products available, and they usually differ
according to the kind of dying agents involved in the chemical
process. Hair dyes can be classified in accordance to time the
color will remain on the hair. Therefore, gradual, temporary,
semi-permanent, and permanent hair coloring products are to be
found.
The wide variety of natural color that can be achieved by varying
the quantity and relative amount of melanin content is immeasurable.
There are available diverse hair coloring products, both natural
and synthetic. Henna is one of the most common natural hair coloring
products. Henna colors the hair with an orange-reddish shade.
However, natural coloring provides a poor color range, making
if difficult to foretell intensity. On the contrary, synthetic
hair coloring products are much preferred because they provide
a greater quality of color and the results are much more predictable.
Gradual hair coloring products employ metallic dyes among which
are salts of lead, bismuth, or silver. These hair dyes can only
darken the hair, with a restricted shade range. Continued use
is required since, in a few weeks, the hair color steadily changes
from gray to yellow-brown to brown-black.
The benefits of gradual hair dyes are that they are cheap and
can be administered at home. However, the color quality may be
poor and unpredictable. Besides, after metallic dye treatment,
the hair usually becomes stiff, dull, and brittle. Moreover, it
will not be possible to practice other chemical processes due
to pre-existing hair damage and to the deposition of metals in
the cortex and on the cuticle, which will interfere with other
treatments resulting in poor outcomes. There are, however, some
professional products designed to eliminate metals from hair shafts.
Still, this is a terribly damaging process to the hair. It would
be preferable to let the hair grow before bearing any other treatment
with hair coloring products in mind. Gradual hair coloring is
predominantly used by men who want to subtly darken their hair.
Temporary hair dyes are acidic textile, water soluble dyes of
high molecular weight. Since these large molecules cannot penetrate
the hair shaft, deposition is only temporary until they are rinsed.
The dye is generally removed one shampoo. But if hair is treated
chemically, it becomes more porous and allows the dye to gently
penetrate into the shaft, permitting longer lasting results. Temporary
hair coloring products are harmless and rarely cause irritation.
Temporary hair coloring products can come as rinses, gel, mousses,
and sprays, and can be used for several reasons, such as to achieve
special effects, brighten a natural or dyed shade, or cover small
amounts of gray hair. These hair coloring products can also be
used by gray haired people with good results. Rinses are to be
administered after shampoo and rinsed shortly after. Gel, mousses,
and sprays are used after drying the hair with a towel and are
left on.
Semi-permanent hair dyes are chiefly synthetics. They can provoke
allergic contact dermatitis. The molecules can spread at large
in and out the cortex due to their small molecular weight. This
is why their effect remains longer than temporary dye. However,
this effect can fade after 4 to 6 weeks. Hair shaft damage is
minor. Like with temporary hair coloring products, on previously
chemically processed hair, the effect may be prolonged and not
much predictable.
Semi-permanent hair dyes can come as lotions and mousses and
are used on wet have and left on for 10 to 40 minutes before rinsing.
Since semi-permanent hair coloring products can only darken hair,
they are frequently used to cover gray hair, add highlights, or
remove unwanted hair tones. Gray haired people can also use these
products with good results as well.
Permanent hair coloring products can either lighten or darken
natural hair color and can cover any amount of gray. Since the
dye will remain permanently until hair grows out, the process
is irreversible.
Since the color develops from an oxidation process in the hair
shaft, permanent hair dyes may damage the hair. Permanent dyeing
consists of three components: primary intermediates, couplers,
and oxidants. Primary intermediates create color on oxidant. Couplers
work by reacting with the products of oxidation of the primary
intermediates to form dyes. Hydrogen peroxide is the oxidant most
usually used.
People who want to color their hair to a lighter shade of blond
should follow two steps. The hair must first be bleached to the
desired shade so that a dye is applied in order to reach the final
blond color. Both these steps damage hair considerably.
Other kinds of hair coloring products are bleaching products.
In fact, bleaching implies partial or complete decoloring of the
natural melanin content of the hair. The most commonly employed
method makes use of an alkaline solution of hydrogen peroxide,
which, when in combination with ammonia used as an alkali, provides
the best bleaching results. Bleaching degree will depend on the
amount of contact time, and is sometimes difficult to control.
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