Our hair starts out with an innate, natural porosity, and our environment slowly increases it over time. This explains why your roots will always be less porous than the tips of your hair.
If you’re not familiar with porosity, you’re not alone. It’s a concept that, until fairly recently, was rarely referenced beyond hair industry insiders and scientists. The birth of the Curly Girl Method, as well as a broader shift towards conscious consumerism in the beauty world, has brought porosity to the attention of everyone who wants to understand and take charge of her hair care.
Porosity is the measure of empty space in a material. A sponge, for example, is highly porous—it's literally designed to absorb water. When we refer to hair porosity, we are talking about how much your hair likes to absorb water and other fluids.
There is more to your hair’s absorbency than the degree of empty space in your hair. The type of material covering the surface of your hair is also an important factor. Imagine if a porous sponge was inserted into a ziplock bag. It doesn't matter that the sponge itself is porous and has lots of void space. The ziplock bag is not porous; it repels water, so it provides a protective barrier to the sponge. The same phenomenon applies to your hair. The cortex, or central component of your hair, will have a certain natural porosity, but on top of that surface are your hair cuticles, which act as a barrier. See our previous blog post on cuticles to learn more.
Cuticles look like shingles on a roof. Your hair has multiple layers of cuticles.
They're bonded together by something called the cuticle-cuticle cell-membrane complex, which acts like cement. It's a fancy name for a compilation of proteins and lipids (fats). A crucial part of this natural hair cement is a component called 18-MEA. 18-MEA is hydrophobic; or put more plainly, it repels water. To illustrate 18-MEA’s effect on hair, imagine taking a piece of paper and covering it with wax. Wax, like 18-MEA, repels water. The more of this 18-MEA you lose, the less likely your hair is to repel water.