Knowing your hairs porosity is incredibly important when it comes to curly hair as it determines how you should treat, manage and care for your curls. Porosity is simply a measure of your hairs ability to absorb and retain moisture. When you consider that moisture is what helps to shape and define curls, then porosity is essentially the most important factor when considering your curl care routine. By knowing your hairs porosity you can tailor your routine and products to maximize the level of moisture your curls retain and therefore their overall shape and curl pattern.
Hair is made of 3 parts as you can see on the diagram above. There is the medulla in the centre, the cortex and the cuticle which makes up the outer layer. The cuticle protects the hair by forming a protective overlapping layer which looks similar to how tiles are laid on a roof. The cuticle forms a line of defence against damage, it gives hair its mechanical strength and it protects the softer inner cortex and medulla.
There are 3 levels of porosity and they are all related to the condition of the cuticle layer of hair. Hair texture is not an indication of its porosity as different degrees of porosity can be found in all hair textures.
If the cuticle lays flat and is compact it means that moisture can’t penetrate or exit the shaft meaning it has a low porosity. In this type of hair there is a tendency for products to be repelled rather than absorbed.
If the cuticle is raised then moisture can easily enter and exit the strand meaning it has a high porosity. Although overly porous hair absorbs product quickly, it is actually often dry because the open cuticle means product is not retained within the hair shaft. Overly porous hair can result from using harsh products e.g. sulphates, chemically colouring or straightening or from heat damage to name a few. This damage makes high porosity hair dry, fragile and brittle.
In normal porosity hair the cuticle is neither flat nor too raised but is at the perfect position for moisture to enter the shaft and remain there.