Nowadays, we’re placing more and more emphasis on hair care routines, and on adapting hair care routines to the unique characteristics of each person’s hair: whether you have a sensitive, dry or oily scalp, whether you have straight or curly hair, chemically processed or not, and so on. A characteristic that has become increasingly popular is hair porosity, but it’s not always obvious to understand what it is, or how it plays into the behavior of your hair.
To help you better understand hair porosity, let’s start from the beginning: the structure of your hair, and what it means for it to be more or less porous.
What is hair porosity?
Hair porosity sounds like a very complicated thing, but it’s actually quite simple: it’s a measure of how permeable your hair is. Simpler still: it’s your hair’s ability to absorb and retain moisture.
To help you understand this, let’s look into the structure of the hair for a second. A single hair strand is composed of three layers: the medulla, which is the innermost layer; the cortex, which forms the bulk of your hair strand and gives your hair its color through melanin; and, finally, the cuticle, the outermost layer, made out of scales that strengthen and protect the hair strand.
According to studies, “the cuticle acts as the hair’s outermost protective barrier, and its destruction makes hair vulnerable to damage.” When we talk about hair porosity, this is what we’re talking about: the permeability of your hair, and consequently its ability to absorb and retain moisture, as influenced by the state and structure of your cuticle layer.
Healthy hair, studies claim, has “a robust cuticle layer” and “relatively low porosity, which makes the hair highly reflective of light, giving it a shiny appearance.” Damaged hair, on the other hand, tends to have higher porosity, because damage to the cuticle layer has made it less impermeable.
Hair porosity and damage
One factor that plays a major role in hair porosity is the level of damage the hair has sustained. Hair that is exposed to frequent chemical processing (think perming, bleaching, coloring, and so on), heat styling, or even excessive environmental stressors such as sunlight or chlorine, for example, often has a compromised cuticle. This translates into a more permeable, less “watertight” strand of hair–in short, higher hair porosity.
But what does it mean for hair to be more porous? Imagine a strand of hair as a hollow tube and you’ll immediately get it: the more porous the outer layer of the tube is, the more communication there is between the inside of the tube and the outside. This means, for example, that it’ll be relatively easy to get water into the tube–aka your hair strand–but it’ll be just as easy for that water to come pouring out again.
This is the nature of high-porosity hair: it’s quick to absorb water, but it loses it just as quickly–which, as you can imagine, may be a challenge to your hair care routine.
Hair porosity in curly hair
In addition to the association between high porosity and damage, there is also an association between high porosity and hair texture–specifically in naturally wavy, curly or frizzy hair. According to the New York Society of Cosmetic Chemists, “textured hair represents a good example of how configuration can influence porosity. Curls and coils are characterized by twists that lead to cuticle lifting at various points along the fiber, and this is more prevalent in the more elliptical hair fibers characteristic of individuals of African ancestry.”
In other words: if you have curly hair, it’s possible that you have high porosity hair not necessarily because of damage, but because of the configuration of your hair strand.
How to identify your hair porosity
If you want to find out whether your hair is low or high porosity, there are several tests you can try at home. They won’t produce scientific results, but they can give you interesting insights about your hair.
One of the most popular tests consists of placing a single strand of hair in a glass of water and waiting to see whether it floats or sinks. According to what we’ve learned, high porosity hair should be quick to absorb water and, therefore, sink; low porosity hair shouldn’t absorb too much water, so we’d expect it to float.
Another common test consists of spraying your hair with a spray bottle of water and seeing what happens. With high-porosity hair, we should expect the hair to absorb the water and then dry relatively quickly; with low-porosity hair, we should expect to see the water gather in droplets on the surface of the hair, without immediate and visible absorption.
As we’ve already mentioned, these are just a couple of tests that you can try out of curiosity. In practice, if hair porosity is something you’re worried about, you’re much more likely to be able to figure it out based on the way your hair behaves on a daily basis.
How low porosity hair behaves
Low porosity often goes hand in hand with healthy hair, especially in less textured hair types. As such, you can expect low porosity hair to look smooth and shiny, an effect of the cuticle lying smooth on the surface of the hair.
A side effect of this smooth outer layer is that it can make the hair so “watertight” that it takes forever to wash and dry. Let’s bring back the tube metaphor: a strand of low porosity hair behaves like a hollow tube with a very thick outer layer. It takes a long time for water to get in, and then a really long time for it to drain out.
In addition, low porosity hair may also resist the absorption of hair care products, resulting in a lot of product buid-up just sitting on the surface of the hair, without bringing any benefit to the inside of the hair strand.
There is no such thing as hair with zero porosity, by the way–to quote a study, all “hair is porous and damaged hair is intensely so.”
How high porosity hair behaves
We’ve already talked about high-porosity hair: typically, this is the type of hair that absorbs water and then throws it right out, thank you very much. Likewise, high porosity hair tends to absorb hair care products easily–the question is whether it’s able to hold on to their moisturizing effects.
If you have high porosity hair, you may notice that your hair dries very quickly after the wash. This can be very convenient, but it’s also a strong indicator that your hair isn’t really holding on to water.
Because of its inability to retain moisture, high porosity hair will typically feel dry to the touch; likewise, it may be frizzy and prone to breakage.
Now that you have a better understanding of what hair porosity is, you can take this characteristic into account when planning your hair care routine: do you have hair that absorbs everything, or hair that absorbs nothing? Is there damage at play, and if so, how can you minimize it?
