Porosity and Elasticity

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 chemical 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 non 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 



ELASTICTY
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.

Overly 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.