How fast does water get into your hair?
Five questions about washing, drying and how a leave-in behaves place your hair on the porosity scale, from low to high. You get a score out of 10 points, a drawing of what the cuticle is doing, and five care habits for that reading.
How long does your hair take to feel fully wet in the shower?
Think of a normal wash, before any product goes on.
Medium
balanced
- 0 to 3Low
- 4 to 6Medium
- 7 to 10High
Five care habits for this reading
Porosity describes the hair shaft, not the scalp. Hair that comes out in handfuls, a widening parting, patches, itching, flaking or soreness belongs with a dermatologist.
How it works.
- Answer five questions about how your hair behaves in the shower, while it dries and after a leave-in.
- Read your porosity, the score out of 10 points and the drawing of the cuticle that goes with it.
- Take the five care habits for that reading, and check again after a colour service or a summer of sun and salt water.
What porosity describes
Every hair is wrapped in 5 to 10 overlapping layers of flat keratin cells, laid from root to tip like roof tiles. That wrapping is the cuticle, and porosity describes how it sits: flat and tight, and water needs time to get through; lifted or chipped, and it passes in seconds. Heat above about 185 degrees Celsius softens keratin and lifts the scales, bleach dissolves part of the outer layer for good, and brushing hair while it is wet chips the edges. Hair grows about 1 cm a month, so the ends of shoulder length hair are 2 to 3 years old and carry every wash and every hot tool of that time, which is why one strand is often low porosity at the scalp and high at the tip. The porosity guide sets out what each reading changes in a routine.
Why the float test fails
A strand dropped into a glass of water reports on surface tension and residue, not on the cuticle. A clean dry hair laid on the surface can sit there for 3 to 5 minutes whatever its porosity, because the water film carries it. Conditioner, oil or styling product make it float for longer, a strand pushed under the surface sinks whatever its condition, and the same hair gives you a different answer on a second try. The five observations in this tool come from the moments that do say something: how long the water takes to soak in, how many hours the hair stays damp, and how fast a leave-in disappears.
What this tool is not
Five habits are not a strand under a microscope. This check does not grade damage, measure protein loss or name a product, and two people with the same reading can need different amounts of oil. Porosity is a property of the hair shaft, not of the scalp: hair that comes out in handfuls, a parting that widens over 3 to 6 months, bald patches, itching, flaking or soreness belongs with a dermatologist, and the guide to hair loss in women explains which pattern points where. Products have their own clock as well: an opened conditioner or leave-in is usually good for 6 to 12 months, and the open jar symbol on the tube gives the number.
Frequently asked.
Why does the glass of water test not work?
What a floating strand measures is mostly surface tension and whatever is left on the hair. A clean dry strand sits on the surface for 3 to 5 minutes whatever its cuticle looks like, silicone or oil makes it float for longer, and pushing it under makes it sink at once. Watch how long your hair takes to get wet and to dry instead.
Can I change my hair porosity?
Only in part. New growth arrives with the porosity your hair is born with, and a cuticle layer that bleach has dissolved does not come back on that strand, so the ends keep their history until they are cut. What you can change is what you add: lower heat, longer gaps between colour appointments, and treatments that fill the gaps for a few washes.
Is high porosity the same as damaged hair?
Usually it is damage from bleach, colour, heat or friction. Some hair is porous by nature though: tightly curled hair has lifted scales at every bend of the strand, which is why curls often need more moisture even when they have never been coloured.
How often should I use a protein treatment?
Every 4 to 6 weeks suits medium porosity, and high porosity takes one every 2 to 3 weeks in turns with a moisturising mask. Low porosity rarely needs protein at all, perhaps every 8 to 12 weeks, and hair that feels stiff or brittle after a treatment has had too much.
Can one strand have two porosities?
Yes, and most long hair does. Hair grows about 1 cm a month, so the ends of shoulder length hair are 2 to 3 years old and have been through hundreds of washes, while the first centimetre at the scalp is new. Answer these questions for the mid lengths and treat the ends as one step more porous.
My hair is falling out. Does porosity explain that?
No. Porosity describes the shaft of a hair that is already growing, not how many hairs arrive or stay. Hair that comes out in handfuls, a widening parting, bald patches, itching, flaking or a sore scalp belongs with a dermatologist.
Guides behind this tool
Beauty
Hair porosity: the test and what it changes in your care
Beauty
Hair loss in women: shedding, pattern loss and what helps
Beauty
When make-up expires: the open jar symbol and 30 monthsMore tools
The Hair Porosity Check reads five everyday observations, not a strand under a microscope, and it estimates rather than measures. It does not diagnose hair or scalp conditions: hair loss, a widening parting, itching, flaking or soreness belongs with a dermatologist. This page is for general information and does not replace advice from a dermatologist, physician or qualified practitioner.