Updated: Mar 18
In order to understand what is the porosity of the hair, we need to know what is the cuticle.
The cuticle is the outside layer of the hair strand. It is solid and rigid. It is composed by 3-10 layers of scales.
“Hair porosity” indicates how open the scales in the cuticle are, and therefore, in which degree the hair can act as a sponge. Generally, low porosity hair is considered healthy, whereas high porosity hair is weak and need nutrition and moisture.
We have several ways how to determine the hair porosity: the strand float test, the hair spritz test, the glide test… The one we use at the salon is the glide test:
Grab a strand of hair (20-30 hairs) from the top of the head, pulling them upright. Glide the fingers from the tips towards the head. If a mess of hair is dragged to the roots, the porosity is high. If our fingers slip smoothly through the strand, and there is no t much hair accumulated at the base, then we have low porosity hair.
Why the porosity is important? for many reasons. Some of them are:
- If the cuticles are very open, water is able to move under the cuticles and go out, and it can drag proteins and nutrients out of the hair, so the hair loses nutrients and gets weaker.
- If the cuticles are very open, water is able to move under the cuticles and go out, so if the hair is coloured or treated, the colour will fade quicker.
- The type of styling products depends on it.
Factors that increase the porosity (open the scales of the cuticle):
- Ammonia (because it is alkaline), that is why bleach it can remove colour.
- Hot water.
- Rubbing the hair (during washing, towel,…).
Factors that decrease the porosity (close the scales of the cuticle):
- Cold water.
- Products with acidic pH, like vinegar (that is why a last rinse with vinegar is useful!).
- Conditioners, masks.
- Hot tools and blowdrying, from the root to the tip (although we don’t recommend using this fact as a way to decrease the porosity, there are healthier ways).
- Light oils will help sealing the cuticule.
What the hair needs, according to its porosity? and what it implies?
It is when the scales in the cuticle layer are closed. Low porosity hair is very compact, and has sealed cuticles, that lay flat and do not easily allow moisture or products in or out.
Low porosity hair is susceptible to dryness, however, when the moisture gets inside, it tends to stay longer.
It can also be easily weighed down by product buildup.
Generally, low porosity hair is considered healthy and does not often suffer from split ends.
It is harder to get low porosity hair wet because moisture will often sit on top of the hair shaft, rather than penetrate it. For this reason, individuals with low porosity hair will benefit from applying products after the hair is washed with warm water and shampoo, and still wet, so the scales are open.
Wash the hair at higher temperature (warm, but not hot!).