What is hair porosity?
Porosity describes how easily water and products get into a hair strand, and how long they stay there. The outer layer of each strand, the cuticle, is made of overlapping cells a bit like roof tiles. When they lie flat and tight, water has a hard time getting in, and a hard time getting out. When they are lifted or worn, water rushes in and leaves just as fast.
People usually talk about three levels: low, medium and high. They are not hair types. Straight hair can be high porosity and coily hair can be low porosity. Porosity is about how hair behaves with water, while type is about the shape it takes.
The most common reason hair becomes more porous is wear and tear. Bleaching, relaxers, perms and regular heat styling all rough up the cuticle, and the American Academy of Dermatology lists them among the everyday habits that damage hair. New growth near your roots has had none of that, so it is often less porous than the ends.
How the test reads your hair
The test asks six questions about things you can see and feel on a normal wash day:
- how quickly your hair gets wet in the shower
- how long it takes to air-dry
- whether conditioners sit on top or disappear
- how often your hair has been bleached, relaxed, permed or dyed
- how often you use hot tools
- whether your ends feel different from your roots
Each answer leans toward low, medium or high. Processing history counts a little more than the rest, because it is the clearest cause of higher porosity. The float test, if you do it, counts least of all. The result is the porosity your answers point to most, with the two strongest signs that put it there, and a note on how clear the call was.
How to do the hair porosity float test
- Wash your hair with a clarifying or plain shampoo and skip conditioner, so there is no product on it.
- Once it is dry, take one or two strands from your brush.
- Drop them into a clear glass of room-temperature water.
- Wait about four minutes and look at where they sit.
Floating on top is usually read as low porosity, hovering in the middle as medium, and sinking as high.
Is the float test accurate?
Not very, which is why it is optional here. Oils left on the strand, leftover product, tiny air bubbles, the temperature of the water and even how you drop the strand all change whether it floats. Two tests on the same hair can give different answers. It is a nice thing to try alongside the questions, but it should never be the only thing you go by.
Low, medium and high porosity compared
| Low porosity | Medium porosity | High porosity | |
|---|---|---|---|
| Getting wet | Slow, water beads | A few seconds | Almost instant |
| Drying | Slow | Average | Fast |
| Products | Sit on top, build up | Absorb and last | Vanish, need more |
| Common cause | Natural, untreated hair | Natural or lightly treated | Bleach, relaxers, heat |
| Usually helps | Warmth, lighter products | Keeping it gentle | Moisture, protection, less heat |
Low porosity hair: signs and routine
Low porosity hair is the hair that seems to repel water. It takes a while to get wet, products sit on the surface and it can take hours to dry. The upside is that once it holds moisture, it holds it well.
Things that usually help:
- Use warm water when you wash and condition, and give conditioner a few minutes before rinsing.
- Choose lighter products: lotions and light leave-ins rather than heavy butters that sit on top.
- Clarify now and then if products build up and leave your hair dull or stiff.
- Apply products to damp hair, not soaking wet or dry, so they spread evenly.
Medium porosity hair
Medium porosity hair takes in water and products easily and holds them reasonably well. It is the easiest to care for, and most routines work. The goal is to keep it that way: limit heat and harsh chemical treatments, use conditioner after every wash and handle it gently when wet.
High porosity hair: signs and routine
High porosity hair drinks in water and products and then dries out quickly. It often tangles, frizzes and breaks more easily, especially at the ends.
Things that usually help:
- Condition after every wash. Dermatologists recommend it for everyone, and high porosity hair needs it most.
- Seal in moisture with a leave-in conditioner, then a cream or a light oil on the lengths.
- Cut back on heat and use the lowest setting that works, with a heat protectant.
- Space out bleach and relaxers, and look after your hair between treatments.
- Detangle gently with a wide-tooth comb, starting at the ends.
Can my hair be more than one porosity?
Yes, and it is very common. If you have coloured or heat styled your hair for years, the ends may behave like high porosity while the new growth near your roots stays low or medium. The test flags this when your ends feel rougher than your roots and your answers point to regular processing or heat. In that case, treat the ends more gently and give them extra moisture.
Can hair porosity change?
The porosity of a strand only goes one way over time. Once the cuticle is worn, it does not grow back, but conditioners can smooth it and make it behave better. New hair grows in with its natural porosity. So if damage has made your ends very porous, gentle care and trims gradually replace them with healthier hair.
The limits of a home porosity test
This is a leaning from everyday observations, not a laboratory measurement of your hair. It is useful for choosing a routine, and that is all it claims to do. Our hair porosity guide explains why it is wise to hold any porosity label loosely and watch how your hair actually responds to changes.
Go beyond a label
A porosity leaning tells you where to start. The HairLens app reads moisture, frizz and breakage from your photos zone by zone, so you can see whether a change in your routine is actually working, and it matches products and wash days to how your hair behaves.