How dyes work


Hair dyes can be either permanent or semi-permanent. Both are
easy to apply at home, reasonably inexpensive, and very popular,
but can also be damaging to your hair, especially if they’re not
used properly.
Settling for semi-permanent
Semi-permanent dyes are acidic and are made of small molecules
that can pass through the scales of the cuticle and into the hair
cortex. These dyes are water-soluble and easily washed out. They
may last from one to six weeks, depending on what dyes are used,
but they lose color faster with frequent washings. Semi-permanent
dyes are generally safe and can be used at home. Because they
don’t contain bleach, they can’t lighten hair, but they can darken
graying hair.
If you decide you’re unhappy with your new semi-permanent color,
many home ingredients can help you rinse out the dye. Common
hair rinse ingredients found around the house include tea, beer
(which is also thought to add body to the hair and make it more
manageable), lemon juice, and heavily diluted honey (50 drops in a
pint of water). Rinse with any of these remedies after washing your
hair if you want the dye out faster. The sooner you wash out the
dye, the quicker it will come out.
You may not want to walk around with your hair smelling of
beer, so you can follow up the rinse with a more pleasant smelling
shampoo.
Going platinum
Bleaches oxidize the melanin granules in the cortex of the hair,
causing them to lose their color. This is an irreversible chemical
alteration in the hair itself and can’t be washed out. The most
common bleach for hair is hydrogen peroxide, which can be used
in conjunction with dyes to achieve the desired color.
Bleaches are often alkaline solutions, just like the neutralizing solu-
tions used for perms, which open the scales on the cuticle (for
more on perms, see the later section, “Perming your hair”). When
you bleach dark hair, the small concentrations of phaeomelanin
are resistant to the bleach so it’s not unusual to see a red tinge on
bleached dark hair.
The powerful bleach needed to obtain the platinum blond look will
almost certainly damage the hair cuticle, especially if it takes sev-
eral applications to achieve the desired color, each adding more
damage to the cuticle. The hair loses its silky feel because of the
cuticle damage.
Bleaching also makes hair more porous, which can produce
uneven shading. As new hair grows in its original color at the scalp
level, the entire head of hair often must be bleached again to cover
it, producing more potential damage to the older part of the hair
shaft. Some people just bleach their roots, targeting the hair close
to the scalp but leaving the hair that emerges from the scalp in its
original color.
With repeated bleaching, wet combing is difficult because the hair
cuticle isn’t smooth and has many damaged scales. Back combing
(or teasing) this hair just compounds the problem, producing
mechanical damage and hair breakage as the scales are knocked
off. Bleached hair also swells very easily because it’s so porous,
and hair is much weaker when it’s wet.
Putting on permanent coloring
Permanent hair coloring can be applied to the whole head or just
in select areas for streaks or highlights. Before hair can be perma-
nently dyed, all the existing color has to be removed by a strong
hydrogen peroxide (in a concentration of 30 to 40 percent) that
bleaches out all the melanin granules. This may produce some per-
manent damage to the keratin in the hair cortex, leaving the hair
with a lifeless look.
Ammonia is the alkaline chemical applied to open the cuticle and
allow the hair color to penetrate the cortex of the hair. It also acts
as a catalyst (accelerating the chemical reaction) when the perma-
nent hair color comes together with the peroxide.
Various alcohols and conditioners may also be present in perma-
nent hair color. The conditioners close the scales on the cuticle
after coloring in order to seal the new color to the cortex. Closing
the scales of the cuticle is important to maintain the moisture of
the hair cortex.
The FDA requires that warnings appear on permanent hair color
packaging to alert you to possible damage to your hair if directions
aren’t followed exactly. Read the instructions in the packages
carefully.

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