Semi
permanent hair dyes
Semi
permanent dyes are mostly organic dyes that do not involve a developer
like peroxide to fix the color in the hair fiber. These products,
unlike permanent hair dyes, do not require permanent prior to use,
they can be applied straight out of the bottle. The dyes are called
semi permanent because the coloring changes will survive through
several washes, but eventually the dye will be depleted and require
reapplication. How long it lasts depends in part on the hair dye,
the frequency of hair washing, and also on exposure to environmental
modifiers like sunlight and chemicals in the air.
Semi permanent dyes can produce an immediate change or the change
may be more gradual, developing with time and multiple reapplications.
If the semi permanent dye is left on for a long time (say 30 minutes)
the result may be a full color change. If the dye is left on for
a short time (say 10 minutes) the color change will be more limited,
but repeated application over weekly intervals will gradually deepen
the color to that achieved with the longer, single application.
Because color change is less noticeable with repeated short applications
over time the approach is usually preferred by those with gray hair
and the more self conscious. Sometimes repeated application to get
the desired result is unavoidable as with henna dye. The effects
of henna hair dyes are usually gradual and build up slowly.
The problem with semi permanent hair dyes is that they usually
do not reproduce dark brown and black shades that can be readily
obtained with permanent dyes. Semi permanent dye is better suited
for those who want lighter shades of color and for those with mousy
and gray hair.
Temporary
hair dyes
Temporary hair color dyes are good for people with gray hair. The
colors add highlights or blend streaked hair without completely
changing the natural underlying hair color. Temporary dyes are not
good if you want a drastic change in hair color. There are some
temporary dye preparations available that do impart stronger and
deeper colors, but the end result can look somewhat unnatural. If
you want a more subtle change in color and a simple application
method, temporary dyes are ideal.
Temporary dyes come in liquid and powder form. Mostly the dyes
are acid rinses. This brings the added benefit that the dye process
will remove soap and scum build up on the hair, although you can
get the same result with a lemon or vinegar rinse. Temporary dyes
do not rub off but they will wash out quite readily, even with just
one shampoo.
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