Quick answer: hair porosity is how easily your hair absorbs and holds on to water. Low porosity hair has a tight, flat cuticle, so water and products sit on top: it needs lightweight products, a little warmth and regular clarifying. High porosity hair has a raised or damaged cuticle, so it soaks up moisture fast and loses it just as fast: it needs rich moisture, strengthening care and a sealing cream or oil. Most people can get a good idea of their type with three simple at-home tests.
Ever wondered why a hair mask works wonders for someone else but leaves your hair feeling heavy? Or why your hair still feels dry despite using conditioner? Your hair porosity could help explain why.
What is hair porosity?
Hair porosity refers to how easily your hair absorbs and retains water. It's influenced by the cuticle, the outer protective layer of each strand. When the cuticle is compact and intact, water gets in slowly. When it's worn or damaged, hair absorbs water more readily but loses it more easily too.
Porosity is influenced by genetics, heat styling, bleaching, colouring and chemical treatments. Different sections of your hair can even have different porosity, particularly if your ends are more damaged than your roots.
Low vs high porosity hair at a glance
- Getting wet: low porosity takes a while to get fully wet; high porosity soaks up water almost instantly.
- Drying: low porosity dries slowly; high porosity dries fast.
- Products: low porosity hair finds heavy products sit on top and feel coated; high porosity hair drinks products in but still feels dry.
- Feel: low porosity often feels smooth and shiny but prone to build-up; high porosity often feels rough, dry and frizzy and tangles easily.
- Colour: low porosity can resist colour; high porosity takes colour quickly but fades faster.
The three hair porosity types
Low porosity hair
Low porosity hair has a compact cuticle, making it more resistant to water. Common signs: it takes longer to become fully wet, water beads on the surface, heavy products leave it coated, it's slow to dry and build-up is noticeable.
Medium porosity hair
Medium porosity hair absorbs and retains moisture without much difficulty. It gets wet easily, conditioners work well, it's generally manageable and holds styles.
High porosity hair
High porosity hair has a more permeable cuticle, often caused by bleaching, colour or heat. It absorbs water readily, feels dry, rough or frizzy, and tangles and breaks more easily. Bleached sections are usually the most porous.
These signs are useful clues rather than definitive measurements, as hair thickness, density and condition also affect how your hair behaves.
How do I test my hair porosity at home?
No single test is perfect, but together these give a good picture:
The float test. Drop a single clean, dry strand into a glass of water and wait a few minutes. If it floats, you likely have low porosity; if it sinks slowly, medium; if it sinks fast, high. Treat this as a rough guide: product residue and oils can skew it.
The slip-and-slide test. Run your fingers up a strand from tip to root. Smooth means lower porosity; bumpy or rough means a raised cuticle and higher porosity.
The spray test. Mist a small section with water. If it beads on top, low porosity; if it absorbs quickly, high; if it sits a moment then absorbs, medium.
How to care for low porosity hair
Low porosity hair needs help letting moisture in:
- Choose lightweight products that won't sit on the surface and build up. Leave-In Detangling Hair Milk and the Daily Use range, such as Energizing Hair Mask, hydrate without heaviness.
- Add gentle warmth. Apply masks to slightly warm, damp hair and wrap in a warm towel to help them absorb.
- Clear build-up regularly. A weekly Scalp Exfoliating Cream before shampoo, or Rebalancing Shampoo, resets hair that feels coated. See Scalp scrubs: do you need one?
- Go easy on heavy butters and oils, which tend to sit on top.
How to care for high porosity hair
High porosity hair needs help holding moisture in:
- Layer in rich moisture with the Nourishing range: shampoo, conditioner and mask with organic oat extract, illipé butter and organic coconut oil.
- Strengthen the weakened cuticle. The Restructurizing Hair Mask and Rebuild range support weakened, porous hair. See protein vs moisture.
- Seal moisture in with a leave-in and a cream or oil on the lengths, such as Oil Non Oil or Liquid Crystals.
- Finish with a cooler rinse to help the cuticle lie flatter.
- Always use heat protection, such as Replenishing Thermal Care Serum, so it doesn't get worse.
Bleached hair is usually high porosity: see our guide to caring for bleached hair.
How to care for medium porosity hair
Medium porosity is the easy middle ground. Maintain it with balanced moisture, such as the Daily Use range, plus an occasional mask, and avoid over-processing that would push it towards high porosity.
Porosity and curly hair
Curly and coily hair is often higher porosity, because natural bends in the strand lift the cuticle and make it harder for scalp oils to travel down the lengths. Moisture-rich, layered routines tend to work best. Explore our curls, coils and waves collection, or read find your curl type.
Frequently asked questions
What are the best products for low porosity hair?
Lightweight, water-based products that won't build up: light leave-ins and milks, light masks used with gentle warmth, and a clarifying or rebalancing wash every week or two.
What are the best products for high porosity hair?
Rich, moisturising and strengthening care: a nourishing shampoo, conditioner and weekly mask, a strengthening treatment, and a cream or oil to seal moisture in.
Can you change your hair porosity?
You can't change your genetic baseline, but you can improve high porosity caused by damage. Strengthening and moisture care help, and reducing heat and chemical processing stops it getting worse.
Is high or low porosity worse?
Neither is "bad"; they just need different care. High porosity needs moisture sealed in; low porosity needs help absorbing it in the first place.
Does the float test really work?
It's a popular rough guide, not a precise science. Oils and product residue can affect the result, so use it alongside the slip-and-slide and spray tests.
Is high porosity hair the same as damaged hair?
Not always, but damage is a common cause. Shop damaged & weak hair or dry & dehydrated hair.
You might also like
What does keratin do for your hair?
How to choose the right hair mask
Split ends: causes, treatment and prevention
About the author
Charlotte Read has spent six years in the hair industry with Insight Professional and holds a First Class BSc in Business Management and Marketing. She writes with reference to real salons across social media and the wider Insight community, and draws on the Insight office team, who between them bring over 100 years of combined experience on salon floors.
Where technical expertise is needed, Charlotte consults Lorraine Matic, Head of Insight UK Education, who brings over 38 years of global experience in colour, technique and hair science.