When your hair grows out of your head, it is born perfect. The hair's cuticle lies flat and smooth. When your hair gets damaged, the cuticle begins to open up. Hair with a closed cuticle is non porous. Hair with a cuticle that is open, or missing chunks is porous. Some hair is naturally susceptible to damage. Some hair will become porous from sun damage, wind damage, etc. But...perming, coloring, flat irons, etc. are common causes of porous hair.
Non porous hair (Low
porosity)- Is hard to get wet. Water runs off it like off a
ducks back. Non porous hair takes a long time to dry (8 hours-ish). It
is hard to get water into the closed cuticle, but once the water is in
there, it is locked in tight. In other words, it is hard to wet and
takes a long time to dry. It will sometimes squeak when you run
your hands over dry hair. Non porous hair is resistant to color, but
once is is colored, it won't fade. It is also resistant to perming or
straitening. These solutions will have to be left on the hair longer
for them to be effectively penetrate the closed cuticle. Low porosity
hair is healthy hair. It is
shiny, especially if it is dark. Hair products seem to sit on top of
porous hair and does not soak in.
Normal porosity hair- Is relatively easy to deal with. It takes perms
and color treatments predictably. If you always get the color on the
box, this is a sign you are normal porosity. It dries at an average
rate (3-4 hours-ish).
Porous hair (High porosity)- Is easy to get wet. Porous hair dries quickly (1-2
hours-ish) without product. With conditioner and gel, it may take a
long time to dry. Porous hair soaks up hair products like a sponge.
Porous hair will dye darker then the box (if dying hair a darker color
then your natural color). However, the color will fade quickly. Perms will
take curlier then expected, but then relax quite a bit. Porous hair is
damaged hair, but that doesn't necessarily mean that your were doing
terrible things to your hair. Some hair is just naturally susceptible
to damage or has natural kinks that make it porous. Porous hair tends to be dull.
I should note that the drying times are my guestimations, no actual science involved. Drying times are based
on hair without conditioner or gel. Products can greatly increase the
drying time. Drying times will also be affected by length, thickness,
humidity, temperature, etc.
If you read around on
NC.com, you may come across the float test. IMHO, this test is
notoriously inaccurate. I'd call it phoney bologna. My porous hair
literally floated for days.
The Natural Haven: Junk Science- Hair Porosity Tests/Float or Sink
My porous hair will get wet from the steam when sitting in a hot bath.
My hair will dry in an hour or two without product, but will take all
day to dry when I used a heavy conditioner and lots of gel. I need lots
of conditioner and gel for my hair because it soaks it up. When I dyed
my hair darker with a permanent dye, it would dye much darker then the
woman on the box. Then the color would fall right out of my hair. All
the color would be completely gone in three weeks. When I used to perm
my hair (darn 80's) I would look like a poodle the first few days, and
then my hair would relax to a normal perm. The first day people would
always say "Oh, you got your hair permed. It looks....um...nice?" Then
I'd say "Don't worry. It won't look like this in a few days." The
right hair products have gone a long way to help me with my porous hair.
For more info, I love this curl chemist article. All of her articles are interesting. You may also like reading The Natural Haven: Porosity: Definition and Causes
Take a hair from you head and firmly grasp each end. Stretch it gently.
If it breaks, it has low elasticity.
If is stretches up to 1/3 of its length and returns to its normal shape, it has normal elasticity. Good for you.
If it streeeeeeeetches and does not return to its original shape, it is overly elastic.
elastic hair is a sign of over conditioning (too much moisture). Low
elasticity is often a sign of dry hair, but can have more complex
causes. You can do the elasticity test
on dry or wet hair. You may find it easier to take a few shed hairs and
sort of twist them together and then pull on the whole wad of hair.
This is an easier way to test my super fine hair. It is very hard to
grasp just one of my hairs.