Hair Porosity: How to Test It and Care for Your Type
Hair porosity is the reason two people can use the same conditioner and get opposite results: one gets soft, glossy lengths, the other gets a greasy film or hair that feels dry again by lunchtime. It describes how easily water, oils and conditioning ingredients get into your hair and how long they stay there. Once you know your type, choosing products gets much simpler.
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Hair porosity is how readily each strand absorbs and holds on to water and product, and it depends mostly on the state of the cuticle, the overlapping outer layer of the hair. Low porosity hair has a tight cuticle that resists moisture; high porosity hair has lifted or damaged cuticle that soaks water up and loses it fast. Heat, bleach and colour raise it, and you cannot reverse it, only manage it.
Key takeaways
- Porosity describes how easily water and conditioning ingredients get into the hair fibre and how quickly they leave again.
- A peer-reviewed review in the International Journal of Trichology (2015) notes that hair is naturally porous and damaged hair is intensely so.
- Bleached and chemically treated hair is more porous than untreated hair and attracts more conditioning ingredients.
- The popular glass-of-water float test is not a validated measurement; how your hair behaves on wash day tells you more.
- Porosity is a hair-fibre issue: it can explain breakage and frizz, but it does not cause hair loss or shedding from the scalp.
What is hair porosity?
Hair porosity is a measure of how easily water, oils and conditioning ingredients pass through the outer surface of the hair into the fibre, and how long they stay. Each strand has three layers: the cuticle on the outside, the cortex that gives hair its strength and colour, and in thicker hairs a soft central medulla.
The cuticle is made of flat, overlapping cells that sit like roof tiles. When those tiles lie flat and tight, water struggles to get in, which is low porosity. When they are lifted, chipped or worn away, water rushes in and escapes just as quickly, which is high porosity. Most people sit somewhere in the middle, and many have a mix: fairly low porosity near the roots and higher porosity at the older, more weathered ends.
A review of hair cosmetics published in the International Journal of Trichology in 2015 puts it plainly: hair is porous, and damaged hair is intensely so. That is why porosity is less a fixed type you are born with and more a record of what your hair has been through.
What are the three porosity types?
The three porosity types are low, medium and high. They are points on a scale rather than strict boxes, and each one tends to show a recognisable set of habits on wash day, which is a more useful guide than any single test.
| Porosity | What the cuticle is doing | How hair behaves | What usually helps |
|---|---|---|---|
| Low | Tight and flat | Takes ages to get wet and to dry; products sit on top and build up | Lightweight products, warmth to help conditioner in, clarifying now and then |
| Medium | Mostly flat with some lift | Takes colour and styling well; holds a style | A balanced routine; protect it from heat and bleach damage |
| High | Lifted, chipped or worn | Soaks up water fast, dries fast, frizzes, tangles and snaps | Richer conditioners, masks, oils to seal, low heat and gentle handling |
Curly and coily hair often tests as higher porosity at the ends, because each bend in the strand is a spot where the cuticle lifts and wears. Fine, straight hair that has never been coloured often sits at the low end. Neither is better or worse; they simply want different products.
How do you test your hair porosity at home?
You test porosity at home most reliably by watching how your clean hair behaves over two or three wash days, rather than by one quick trick. Notice how long it takes to get fully wet in the shower, how long it takes to air dry, and whether conditioner seems to vanish into it or sit on the surface.
The famous float test, dropping a clean shed hair into a glass of water and seeing whether it sinks, is everywhere online. It is fun, but it is not a validated measurement. Leftover oil or conditioner, the thickness of the hair and even the surface tension of the water change the result. Read it as a hint, not a verdict.
A better at-home check has four steps:
- Start clean. Wash with a gentle shampoo and skip conditioner this once.
- Time the soak. Hair that is still dry underneath after a minute under the shower leans low porosity. Hair that is soaked in seconds leans high.
- Time the dry. Hair that is still damp many hours later leans low; hair that is dry and frizzy within an hour or so leans high.
- Slide test. Run finger and thumb from end to root along a single strand. Smooth suggests a flat cuticle; bumpy or rough suggests lifted cuticle and higher porosity.
Test the ends and the roots separately
If your roots behave one way and your ends another, you have mixed porosity, which is very common in long or coloured hair. Care for the lengths you actually have: lighter products at the root, richer ones on the ends.
What makes porosity go up?
Porosity goes up when the cuticle is lifted or worn away, and the main causes are bleaching and colouring, high heat from straighteners and dryers, chemical straightening or perming, sun and chlorine exposure, and rough handling such as harsh towel-drying and brushing wet hair. Age matters too: the ends of long hair may be several years old.
The same 2015 review explains that bleached and chemically treated hair has more negatively charged sites on its surface and is more porous than untreated hair, which is why it grabs conditioning ingredients so readily. That is useful: high porosity hair responds well to conditioner because it has more places for conditioner to attach.
Once the cuticle is damaged it cannot grow back, because the hair fibre is not living tissue. Only new growth from the scalp arrives with an intact cuticle. So the realistic goals are to stop porosity rising further and to make the existing lengths look and feel better. Our guide to what causes hair damage breaks down the four main culprits.
How should you care for low porosity hair?
You should care for low porosity hair with light products, a little warmth and regular clarifying, because its tight cuticle lets water and conditioner in only slowly and lets heavy creams sit on the surface. The usual complaints are build-up, limp roots and conditioner that never seems to sink in.
- Apply products to damp, warm hair. Conditioner goes in more easily straight after a warm rinse than onto cool, half-dry hair.
- Use warmth for deep conditioning. A shower cap or a warm towel for 10 to 20 minutes helps a mask work on low porosity lengths.
- Choose lighter oils. A few drops of a light oil beat a thick butter that coats the hair.
- Clarify now and then. Build-up is the main enemy, so a clarifying wash every few weeks resets things.
Protein-heavy treatments can leave low porosity hair feeling stiff, so use them sparingly. Rice water is a good example: our guide to rice water for low porosity hair explains why it needs care on this hair type.
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How should you care for high porosity hair?
You should care for high porosity hair by adding moisture with rich conditioners and masks, sealing it in with an oil, and cutting down on the heat and friction that lifted the cuticle in the first place. High porosity hair drinks water quickly and loses it just as fast, which shows up as frizz, tangles and breakage.
- Condition every wash. Rinse-out conditioner is non-negotiable, and a weekly mask helps the lengths feel smoother.
- Seal with oil. A small amount of oil on damp ends slows water loss and reduces friction.
- Turn the heat down. Air dry where you can, use a heat protection spray every time, and keep straighteners at the lowest setting that works.
- Handle it gently. Detangle with conditioner in, from the ends upwards, and blot with a soft towel instead of rubbing.
- Try low-friction styles. Loose braids and satin or silk pillowcases cut down on the rubbing that snaps weakened ends.
Our step-by-step guide to using conditioner properly shows how much to use and where to put it.
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Does hair porosity cause hair loss, shedding or breakage?
Porosity can contribute to hair breakage, but it does not cause hair loss or hair shedding, because those happen at the root in the scalp while porosity is a property of the hair fibre above it. Mixing the three up leads people to buy the wrong products for the wrong problem.
| Problem | What is happening | Where porosity fits |
|---|---|---|
| Hair breakage | The fibre snaps part-way along, leaving short broken pieces and split ends | Directly linked: high porosity hair is weaker, drier and snaps more easily |
| Hair shedding | Whole hairs fall out from the root, often two to three months after illness, childbirth or stress | Not linked; the NHS says losing 50 to 100 hairs a day is normal |
| Hair loss | Follicles produce finer, shorter hairs over time, or hair is lost in patches | Not linked; see a GP if you are worried |
A quick way to tell breakage from shedding is to look at the hairs you find in your brush. Shed hairs are full length with a small white bulb at one end. Broken hairs are short, uneven and have no bulb. If you mostly find broken pieces, porosity care, gentler handling and less heat are the right focus. Our guide to preventing split ends goes deeper on the breakage side.
Can you change your porosity?
You cannot permanently change porosity, because the cuticle on existing lengths cannot repair itself, but you can make porous hair behave better and stop it getting more porous. Conditioners do this by smoothing and coating the cuticle, which the 2015 review describes as neutralising the negative charge on the hair surface and lubricating it.
A separate review in the same journal (2014) explains that hair has a very low isoelectric point, below pH 4, and concludes that lower pH shampoos may cause less frizz because they generate less negative static electricity on the fibre surface. That is one reason gentle, slightly acidic cleansers and conditioners suit high porosity hair.
Everything else is protection. New hair grows at roughly a centimetre a month, so the porous ends you have today are gradually replaced by healthier-looking lengths if you stop adding damage. Regular trims remove the most porous ends before they split further up the strand.
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When should you see a GP instead?
You should see a GP instead of changing your hair routine if your hair is coming out from the root in clumps or patches, your scalp is sore, scaly or bleeding, or your hair has changed suddenly alongside other symptoms such as tiredness or weight change. The NHS advises seeing a GP if you are worried about hair loss. Watermans does not offer medical advice. If your question is about products or a routine rather than a medical one, you can talk to Gail Waterman, our co-founder, as an AI avatar on the Watermans homepage. For how protein ingredients coat and smooth damaged strands, see our guide to peptides in hair care.
What are the frequently asked questions about hair porosity?
Is the float test for porosity accurate?
Not reliably. Oils, conditioner residue and the thickness of the hair all change whether a strand floats or sinks. Watching how your hair gets wet and dries over a few wash days is a better guide.
Is high porosity hair damaged hair?
Usually yes, at least in part. Bleach, colour, heat and friction lift the cuticle, which raises porosity. Some curly hair is naturally more porous at the ends too.
Can low porosity hair become high porosity?
Yes. Bleaching, frequent heat styling and chemical straightening can lift the cuticle, so hair that started low porosity can become high porosity at the ends.
Should low porosity hair avoid protein?
Not entirely, but go easy. Heavy protein treatments can leave low porosity hair feeling stiff or straw-like, so use them occasionally and follow with a moisturising conditioner.
Do oils add moisture to hair?
Oils do not add water, but they help slow its loss and reduce friction. Apply a small amount to damp ends after conditioning to seal in moisture.
How often should I wash high porosity hair?
Many people with high porosity hair wash two or three times a week with a gentle shampoo, always followed by conditioner. Washing daily can leave it drier.
Does porosity change with age?
It can. Older lengths have had more exposure to heat, sun and brushing, so the ends of long hair are often more porous than the roots.
What is the bottom line on hair porosity?
The bottom line on hair porosity is that it explains most of the frustrating things hair does on wash day, and it is mainly a record of cuticle damage rather than a fixed type. Low porosity hair wants light products and a little warmth; high porosity hair wants rich conditioning, oil to seal and far less heat. Work out your type from how your hair behaves, care for the ends and roots separately if you need to, and keep sudden or patchy hair loss for your GP.
If your hair soaks up water and frizzes by lunchtime, a weekly deep-conditioning hair mask is the simplest place to start.
Sources & references
- Gavazzoni Dias MF, Hair cosmetics: an overview, International Journal of Trichology, 2015 (PubMed Central), checked 18 September 2026.
- Gavazzoni Dias MF and colleagues, The shampoo pH can affect the hair: myth or reality?, International Journal of Trichology, 2014 (PubMed Central), checked 18 September 2026.
- NHS, Hair loss, checked 18 September 2026.
- StatPearls, Physiology, Hair (NCBI Bookshelf), checked 18 September 2026.
Watermans products are 100% cosmetic and do not treat medical hair loss. Individual results may vary.
