(Classical music)
- This is not my natural hair color.
There are three basic
chemical formulations of
hair dye.
Temporary, semi-permanent, and permanent.
Before we look at what
each of them do, let's
look at the physical structure of hair.
Hair is deadstuff.
Three layers of slightly
different dead stuff.
The core, called the
medulla, is not pertinent to
our interest today at all.
But it's surrounded by a
thick layer of cells called
the cortex, no relation
to your brain's cortex.
It's where you find the
pigmented melanin proteins
that give hair its color.
Protecting the cortex is
hair's outermost layer,
the cuticle.
As hair's armor, it's made
up of overlapping scales.
Temporary dye just sticks to the cuticle.
It's more like paint really,
and it'll usually circle
the drain with your next shampoo.
- Semi-permanent dye
contains molecules of pigment
so tiny, that they can slip
between the scales of the
cuticle and stick to the cortex.
But it's still more paint-like.
It doesn't chemically react
with anything in the hair.
So, a semi-permanent dye
lasts about 12 shampoos max.
Permanent dye, as the name
suggests, is designed to
stay with your hair until
the hair grows or falls out.
In general, permanent dye
consists of two solutions.
First, an alkaline chemical
plus two types of particles
that will come together
to form the new color,
dye precursors and dye couplers.
Second, the developer.
An oxidizer, usually a weak
solution of hydrogen peroxide.
You, or your salon
professional, mix the two
together right before
applying them to your hair.
The alkaline chemical,
either ammonia or a more
gentle substitute, goes to
work opening up the cuticle.
For dye to be most
effective, it needs to access
hair's cortex.
Alkaline stuff temporary
softens and relaxes the
cuticle's scales.
The next hurdle in achieving
a new hair color is
getting rid of some of the
existing color, the melanin in
the hair's cortex.
Enter the developer.
It oxidizes the melanin
molecules, breaking melanin's
double carbon carbon
electron bonds and giving
up one of it's own oxygen
atoms to fill in the space.
The result?
The melanin turns colorless
and releases sulfur atoms.
That's right, part of
permanent dye's characteristic
stink isn't actually the
dye at all, but an element
of your hair passing into the air.
But that's not the developer's only job.
It also kicks off the
reaction that brings together
the new color molecules by
oxidizing the dye precursors.
These are usually colorless
chemicals that develop
color when oxidized.
The resulting pigmented
particles, called intermediates,
are monomers that, left
to their own devices,
would slip through the cuticle scales like
semi-permanent dye.
But, the dye couplers react
with the intermediates to
form polymers of pigment
that are too big to
just slip back out.
That's how permanent color
resists fading through
multiple washes.
It's trapped beneath the cuticle.
So, that answers today's
question, but I've got
one for you.
What hair color do you most want to try?
I am thinking about going to purple, but
aside from that, I think
I would look very fetching
with some eyebrow
tinting as a honey blonde
and a perm.
