The outermost layer of hair is called the cuticle. Under a microscope, resembles overlapping scales. These scales can open and close like window blinds. Its purpose is to prevent or allow penetration of moisture and air (or anything else that touches the surface).
Hair porosity relates to the ability of the hair to absorb moisture through the cuticle layer. Your hair has the ability to absorb up to 50% of its weight when its wet. The degree of porosity is directly related to the state of the cuticle layer. Healthy natural hair with a closed and compact cuticle layer is resistant to penetration. Porous hair has a raised cuticle layer that easily absorbs moisture. As hair grays, the cuticle closes and the hair often becomes what is called "resistant" or "low porosity"
If you have low porosity hair, you will require a more alkaline solution in order to have the product penetrate your hair. Conversely, if you have high porosity hair, you are better off with an acidic mixture to gain penetration. Alkaline solutions open the cuticle while acidic ones close it.
The normal state of the cuticle is almost closed, allowing for some penetration. Conditioners and chemical processes normally work by opening the cuticle to allow penetration of the product deep into the hair shaft and depending on your hair’s porosity, the mixture needs to be adjusted for maximum effect. So in this regard it is important to know your hair’s porosity.
HOW DO I CHECK MY HAIR POROSITY?
You can generally check for your hair’s porosity with a feel test. Divide your hair into 4 quadrants (example, crown, temples nape, forehead hairline). One quadrant at a time grasp several hairs between your forefinger and thumb and run your fingers up the strand from the end to the scalp.
If the hairs feel very smooth and the cuticle is hard and compacted, your hair is considered to be resistant, or of low porosity.
If the hairs feel slightly rough, it is considered porous, or normal.
If the hairs feel very rough, and in both directions, it is considered highly porous and may even be damaged or over-processed.
HAIR POROSITY WATER TEST
A more accurate way to check for porosity is the water test. Place a few strands of clean hair into a tall glass of room-temperature water and observe what happens. Make sure your hair does not have any product on it, or a leave-in when doing this test.
Normal, healthy hair should float or only sink slightly. The rate at which the hair sinks is indicative of the speed of which it absorbs and loses moisture. The faster the moisture is absorbed into the hair, the more porous it is, and that translates to the more porous it is, the faster it loses moisture.
Normal hair absorbs moisture at a slow pace and should be capable of holding it for long periods of time. If hair absorbs enough moisture within one minute to cause it to sink in water, it is absorbing way too fast and there is a problem. If you have this hair type you will already have noticed breakage and a lack of elasticity in the hair.
Hair Position after 1 min = Meaning
Floats = The hair is impermeable or low porosity.
Sinks – Middle of the Glass = The hair is normal.
Sunk – At the Bottom of the Glass = The hair is highly porous and possibly damaged.
A simpler way to check is to brush or comb through a section of hair and while holding it taut, mist water on it with a spray bottle. If the water is absorbed into your hair quickly and disappears, it is porous. If it stays ont he outside and beads up, it is resistant. Healthy hair is somewhere in between.
WHAT CAN I DO ABOUT MY HAIR’S POROSITY?
There are products you can use to increase or decrease your hair’s porosity, within reason. For hair that is low porosity or impermeable, you will need to use an alkaline product before using a conditioner or moisturizer in order to soften and open the cuticle to be receptive to the product, or the product will just sit on top of your hair and not soak in.
Overly porous hair tends to look and feels dry, but actually, it can absorb great amounts of water! You will often feel your hair is like a sponge full of water. It just can’t hold on to it for long. You need to change its porosity so it can hold on to moisture in the products you use. In this regard, protein-based products are good for porous hair because they help repair the cuticle layer, filling in missing gaps. However, don’t get carried away because too much protein will dry your hair out even further. You can use a deep conditioner after your protein conditioner, to reduce the negative effects of the protein.
Apple Cider Vinegar is also excellent for porous hair as it closes the cuticle on contact. You can make your own ACV rinses and there are recipes on Nappturality to help you.
The key to increasing your hair’s porosity to absorb conditioners and treatments is warmth. Invest in a steamer and use it when you are applying your conditioning treatments to gently open the cuticle and allowing the conditioner to penetrate into the hair shaft. Warmth also puts (lowers) the surface tension of water into a favourable condition for absorption. So by adding an EO to your hair steamer you will experience better results.
Using a castile soap-based shampoo is also a good way for low porosity hair to open up for more moisture and hydration.
If you want to improve the performance of your leave in or rinse-out conditioner, no matter what your porosity is, just heat up the conditioner before applying to your hair. Don’t heat it to boiling point, just to a hot temperature that won’t burn you. You do not want to break the compounds in the conditioner by boiling it.
So there are ways you can work with your hair’s porosity. The key is finding the balance that works for you.