Porosity has become quite a buzz word lately. It has gained importance as people (especially those with curly hair) have started understanding its relevance to hair dryness. In an attempt to establish the ‘porosity level’ of the hair, many have tried the float test (or hair porosity test). The test result is not straightforward and can create even more confusion. (Like I explained previously, this test is heavily flawed and will not give accurate results). Here we will discuss what porosity is and if high porosity always implies that the hair is damaged.
Porosity is often portrayed as flat or flared cuticles. When one talks of high porosity in particular, the image of a swollen hair strand with fully open layers of cuticles is what comes to mind. This image is accurate for damaged hair. But high porosity in virgin hair doesn’t necessarily have to be due to flared cuticles. Let me explain.
The hair cuticles are bound together by a membrane called the cell membrane complex (CMC). The exact composition of this membrane is not fully understood yet but, it is known to contain lipids, protein matter and moisture. This layer is only a few nanometers thick but it acts like glue and holds the cuticles down.
During chemical treatments the membrane gets compromised causing the cuticles to become loose/lift. One of theoretical pathways for water, shampoo, or other ingredients to enter the hair is through this layer between the cuticles. Another pathway is directly across from the cuticles to the cortex which is harder to do because the cuticles are protected by the hydrophobic (hates water) layer of lipid, 18-MEA.
The bottomline is that the CMC layer determines how much water soluble material can penetrate the hair, which in turn relates to the hair porosity. So high porosity can also be exhibited in virgin hair.
High porosity in damaged hair
The change in porosity from virgin to damaged hair for the same person is dependent on other factors. First of all, in damaged hair the external layer of lipids (18-MEA) on the cuticles are usually damaged or absent. This hydrophobic layer doesn’t like water. When that layer is gone, water or other water soluble ingredients can get access to the cortex of the hair more easily.
Additionally, chemical treatments using high pH cause the hair to swell and damage the CMC layer as well as the cuticles. The damage inflicted, allows less resistance for water or other ingredients to enter (or leave) the hair.
The damage done to the CMC layer prevents it from securely re-bonding the cuticles even after the pH goes down. This is why the cuticles are more lifted and ‘flared’ in damaged hair.
You could have porous hair but not be damaged. But if you have damaged hair, your hair is definitely more porous than untreated hair.