Hair porosity is a word from the salon, not from medicine, but it describes something you can see every wash day: how readily your hair takes in water and how long it holds on to it. Knowing your porosity helps to explain why products sit on your hair, vanish into it, or leave it dry an hour later.
What porosity means
Each hair is covered by the cuticle, a layer of overlapping scales like roof tiles. When the scales lie flat and tight, water and products enter slowly. When they are raised, chipped or missing, water moves in and out quickly.
- Low porosity: tight cuticle. Hair resists water, then holds it well.
- Medium porosity: water enters and stays at a balanced rate.
- High porosity: raised or damaged cuticle. Hair absorbs fast and loses moisture fast.
What decides your porosity
Genes play a part, but damage is the main thing that raises porosity:
- Bleaching and permanent color.
- Relaxers and perms.
- Frequent heat styling.
- Sun, chlorine and rough handling.
Because the ends are older than the roots, they are usually more porous than the rest of the hair.
How to estimate your porosity
There is no precise home test. Observation works better than any single trick.
| What you notice | Suggests |
|---|---|
| Water beads on the hair; it takes a long time to get fully wet | Low porosity |
| Products sit on the surface and build up easily | Low porosity |
| Hair takes hours to air dry | Low porosity |
| Hair wets easily and dries in a moderate time | Medium porosity |
| Hair soaks up water at once and dries quickly | High porosity |
| Hair tangles, frizzes and feels rough; color fades fast | High porosity |
The spray test
Mist a small section of clean, dry hair with water. If the drops sit on top for a while, porosity is probably low. If they disappear quickly, it is probably high.
A note on the float test
A popular test says to drop a hair in a glass of water and see whether it sinks. Oils, product residue and surface tension all affect the result, so it is unreliable. Use it only as a rough hint.
Caring for low porosity hair
- Choose light, water-based products and avoid heavy butters that sit on the surface.
- Apply conditioner to wet hair and give it a few minutes.
- Gentle warmth, such as a warm towel over a deep conditioner, can help it to absorb.
- Use a clarifying shampoo now and then to remove build-up.
Caring for medium porosity hair
- A regular conditioner and an occasional deep conditioner are usually enough.
- Protect it from heat and chemical damage so that it stays this way.
Caring for high porosity hair
- Use richer conditioners and leave-in products to slow moisture loss.
- Layer a leave-in conditioner under a cream or a little oil to seal.
- Rinse with cool or lukewarm water, not hot.
- Reduce heat and space out color treatments.
- Trim damaged ends regularly.
Products containing proteins can temporarily fill gaps in a damaged cuticle and make hair feel stronger. Too much can leave some hair stiff, so alternate them with moisturizing products. Conditioner vs Hair Mask: What's the Difference? explains the difference between a conditioner and a hair mask.
Porosity is one part of the picture
Porosity works together with your curl pattern, strand thickness and density. Fine, low porosity hair needs very light products. Coarse, high porosity hair can take much richer ones. See How to Find Your Hair Type for the other checks, or try the Hair Type Quiz.
Can you change your porosity?
You cannot repair a damaged cuticle for good, because hair is not living tissue. You can make it behave better with conditioning and protect new growth from damage. Bleached hair needs particular care. See Bleached Hair Care: Washing and Conditioning Tips. For curl routines built around moisture, see Curly Hair Routine: A Step-by-Step Guide.
Related on ArniSun
- How to Find Your Hair Type
- Conditioner vs Hair Mask: What's the Difference?
- Bleached Hair Care: Washing and Conditioning Tips
- Curly Hair Routine: A Step-by-Step Guide
- Hair Type Quiz: Find Your Texture and Curl Pattern
Sources and further reading
Frequently asked questions
Is high porosity hair always damaged?
Not always. Some hair, especially very curly and coily hair, is naturally more porous. Damage from bleach and heat raises porosity further.
How often should low porosity hair be washed?
As often as your scalp needs. Low porosity hair is prone to build-up, so regular cleansing and an occasional clarifying wash help products to work.
Does porosity affect hair color?
Yes. Highly porous hair takes up color quickly and unevenly and loses it faster. Tell your colorist about earlier bleaching or heat damage.