Diagnosis

Hair Porosity Test

Answer eight questions about how your hair drinks water, dries and holds color, and get its porosity with the developer, level and timing changes to make before you mix. This test is about coloring: how hair will take color and developer. The reading means the same for curl care, but the advice here is for the bowl.

Free, no sign-up. Runs in your browser. Updated 2026-09-23.

Eight questions

0 of 8 answered. The four everyday questions plus one about the hair itself give a reading.

The eight answers are averaged, not added. An average in the bottom third of the scale is low porosity, the middle third is normal and the top third is high. There is no score to compare against anyone else's.

1. In the shower, how long before the hair is wet right through?
2. Left alone, how long does it take to air-dry?
3. What do conditioners and leave-in products do on it?
4. Slide two fingers up a dry strand toward the scalp. How does it feel?
5. What chemical services has this hair had?
6. When it has been colored, how did the color behave?

Not needed if the hair has never been colored: answer question 5 first and this one switches off.

7. How much frizz and breakage do you see?
8. How often does it see heat: irons, wands, a hot dryer?

Your porosity

Answer the questions and your porosity appears here. The four everyday questions plus one about the hair itself give a reading.

In one line

Porosity is how easily hair absorbs and holds moisture, and color follows the water in. Low porosity takes forever to wet, then holds color once it is in; high porosity is soaked in a second, dry in minutes, grabs color fast and fades it fast. The float test is unreliable on its own, because build-up and surface tension decide what a strand does in a glass.

Fingers sliding up a dry strand toward the scalp to feel whether the cuticle catches
Two fingers slid up a dry strand toward the scalp. Smooth means low porosity, rough and catching means high, and it is one sign of three or four worth checking. Illustration, not a photograph.

Two to five minutes just to get it wet

It shows first at the bowl. Some heads take two to five minutes of water before they are wet through, the water beading and running off while you wait, and the same head is still damp at bedtime after an air-dry. Others are soaked the second the water touches them and dry twenty minutes later. That difference, how fast water goes in and how fast it leaves, is porosity, and color behaves the way the water does.

The reason is the cuticle, the overlapping scales laid down a hair like shingles on a roof. Flat and tight, they let very little in or out. Lifted, chipped or missing, they let everything in and hold nothing.

The signs, in the order they are worth trusting

Water first. Mist a clean, dry section: droplets that sit for a minute or more mean low porosity, droplets that vanish mean high, and a bead that sits and then soaks in is normal. Then product: conditioner that sits on top and leaves the hair coated is a shut cuticle, and conditioner that disappears and leaves it thirsty is an open one.

The finger slide comes after those. Take a clean, dry strand from near the crown, hold the end loosely, and slide two fingers up toward the scalp against the grain, slowly. Smooth and slippery is low. A faint texture like fine thread is normal. Rough, bumpy, catching on your finger is high. One strand can lie, and roughness is sometimes coarse texture or a knot rather than a lifted cuticle, so try three places and read it next to the water signs.

Dry on its own tells you nothing until you know whether the water is failing to get in or failing to stay.

Virgin hair is not automatically low porosity. It only means nothing has been done to open the cuticle, which is why this test leaves the two history questions out when you say the hair has never been colored. And clarify before any of it. Oil, silicone, dry shampoo and leave-in block water, so a head carrying a week of product reads as low porosity in every test there is, including the questions above.

The glass of water

The float test is the one everybody has heard of: drop a strand in a glass, low porosity floats and high sinks. Colorists split on it, and the doubters have the better argument. What decides it is surface tension and whatever coats the hair: sebum, conditioner or styling product keep a strand up regardless of the cuticle, and the water temperature changes the answer. A clarified strand pushed under with a fingertip sinks whether it is virgin or bleached. The ones who keep the test say clean hair, room-temperature water, wait five minutes, and never on its own. Unreliable by itself is the fair verdict: it measures the coating far more than the cuticle.

Low porosity

How it behaves

Smooth to the point of slippery, and it shines on its own because a tight cuticle lies like a mirror. Water beads and rolls off before the hair gives in, it takes hours to air-dry, and conditioner sits on top so you rinse and rinse and it still feels coated.

What it does to color

This is resistant hair, and it takes a long time to process anything. The dye has to get past a shut door, so color comes out a shade lighter and a touch cooler than the swatch, gray looks translucent at first, and everything takes its full time. Once the pigment is in it stays for weeks and fades slowly.

In the bowl

Process the full manufacturer time. Use 20 volume even for deposit on stubborn hair, since 10 volume struggles to lift the cuticle enough for pigment to settle. Hold some warmth in while it processes, a plastic cap under a warm towel at home or a hood in the salon, and for stubborn gray set gray type to Resistant in the gray coverage calculator: the NN version of the shade and the full 45 minutes, which is also the ceiling. Then go half a level warmer than instinct says, because this hair will not grab cool: a 7.1 often reads as a plain 7N, so lean natural or gold over ash.

Normal porosity

How it behaves

A faint texture, nothing you would call rough. Water soaks in after a few seconds, the hair dries in about an hour, products absorb and leave it soft.

What it does to color

This is the baseline. The swatch is roughly what you get and the fade is the one the brand tested on.

In the bowl

Nothing much changes. Ratio by weight, standard developer (10 for demi and toner, 20 for deposit and gray, 30 for lift), standard timing, and the processing time calculator is written for this hair. The one adjustment is the ends, always a touch more porous than the roots, so they go on a few minutes later.

High porosity

How it behaves

Rough and catching, sometimes squeaky. Wet the instant it meets water, dry before the towel is down. Products vanish into it and it still feels thirsty, it frizzes in any weather, and the ends split and snap. It is not automatically damaged hair, some people are born with it, but everything done to a head pushes it this way, and bleach fastest of all. That is what the last two questions read: frizz, breakage and heat say what has been done to the hair, not what its cuticle was born as.

What it does to color

The door is open, so it grabs color fast and grabs the dark, cool part of it hardest: a 7.1 can land as a muddy 6 with a green shadow. Nothing holds the pigment in, so it lets go just as fast, and two or three washes later the brass is back.

In the bowl

Everything comes down, the developer first.

  • 10 volume for a demi or a demi toner; a T18 type liquid toner runs on the 20 vol its bottle names, and on porous hair it runs shorter, a demi toner 5 to 15 minutes instead of 10 to 20. Toner selector
  • Half a level to a full level lighter and warmer than the target.
  • Same total time, first look 5 minutes earlier, ends last.
  • A protein filler or equalizing spray first, so pigment lands evenly. Protein fills the gaps where cuticle is missing, and this hair takes it well.
  • Mix about 10 percent more for porous, lightened lengths. Hair dye amount calculator
  • Ends last, and expect a faster fade whatever you do.

All three on one table

PorosityDeveloperProcessingFormula shift
Low20 vol even for deposit, 30 vol for liftFull time, and no minutes past it. A cap holds warmth and moisture; it changes no numberHalf a level warmer, natural or gold over ash
Normal10 vol demi and demi toner, 20 vol for a T18 type liquid toner, 20 vol deposit and gray, 30 vol liftManufacturer timeNone, ends a few minutes after roots
High10 vol or demi wherever possibleSame total time, first look 5 minutes earlier, ends lastHalf to one level lighter and warmer, filler first
One strand, two porositiesEvery strand is a timeline. The half inch at the scalp grew last month and has never met a bowl of anything. The ends may be three years old, bleached, toned and ironed, their cuticle raised where it is not missing. One formula for one time under-processes the roots and over-grabs the ends. When the answers above point both ways, water saying shut and history saying opened, treat the regrowth as one band lower than the reading and the lengths as the reading itself, with a filler wherever the fingers catch.

It changes, so check again

Porosity is the state of the cuticle on the day you touch it. Chemicals, bleach and heat raise it, almost always toward the high side regardless of where the hair started, and a few stylists add hormones, pregnancy and medication to the list. A full bleach, a relaxer, a keratin smoothing, a summer of salt water: each one moves the answers above. So the head that was normal two summers ago may now be three porosities at once, low at the scalp and high through the ends. Check again before any color you care about, and always after the big services, on clean hair with nothing on it.

What people ask about porosity

How do I know if my hair is low or high porosity?

Watch it at the sink first. Hair that takes forever to get wet, water beading on top, and is still damp hours later is low porosity. Hair that is soaked the second it meets water and dry twenty minutes later is high. Then slide two fingers up a clean dry strand toward the scalp: smooth and slippery is low, a slight texture is normal, and rough or catching is high. Do two or three of those on clarified hair, since product build-up makes any hair read low.

Is the hair porosity float test accurate?

Not on its own. Whether a strand floats is decided by surface tension and whatever is coating it: sebum, conditioner, oil and dry shampoo keep a hair up regardless of its cuticle, water temperature moves the result, and a clarified strand pushed under with a fingertip sinks whether it is virgin or bleached. Most colorists call it unreliable. The ones who still use it say clean strand, room-temperature water, wait five minutes, and read it next to how the hair wets and dries.

What developer should I use on high porosity hair?

The lowest that does the job. The cuticle is already open, so demi and demi toners go on 10 volume and a T18 type liquid toner on the 20 vol its bottle names. The first look comes 5 minutes earlier, and the total time stays where the leaflet puts it. 20 volume is for gray coverage on the regrowth only, kept off the porous lengths.

Why does low porosity hair not take hair dye?

The cuticle scales lie flat and tight, so the dye has to work to get under them, and this hair takes a long time to process anything. Color comes out lighter and cooler than the swatch and gray looks see-through at first. Process the full time and do not add minutes past it, use 20 volume even for deposit, hold some warmth in with a cap, and formulate half a level warmer, because it will not grab cool tones easily. The gray coverage calculator covers the stubborn-gray side of that.

Should I use a protein filler before coloring high porosity hair?

Yes, when the hair is uneven or very porous. High porosity hair takes protein well because it fills the gaps where cuticle is missing, and a filler or equalizing spray does the same job for color: pigment lands evenly instead of pooling in the most porous spots, which is what causes dark patches and banding on lightened hair. Apply it to towel-dried hair, then color with 10 volume or a demi, ends last.

Can hair be low porosity at the roots and high porosity at the ends?

Very often, and it is the most common reason one formula gives two results on one head. The hair up top grew in the last few weeks and has never been touched, while the ends may be three years old and have seen bleach, sun and heat, and everything done to hair pushes it toward the high side. Treat them as two heads: the tool says regrowth is virgin hair and often reads one band lower, so 20 volume and full time on the regrowth, 10 volume or demi through the lengths with the first look earlier, ends last.

Keep going with these

A gloved hand holding a parting open with a comb to see how much of the regrowth is white Diagnosis Gray Coverage Calculator How much natural goes in the bowl, 20 vol or 10, and how long to leave it on for the gray you see. Color squeezed from the tube into a bowl on a digital scale, the developer bottle waiting beside it Formulation Developer to Color Mix Calculator Exact grams or ounces of color and developer for any ratio, from a 10 g touch-up to a full bowl. Three bowls of mixed color in different amounts, next to a scale and a measuring jug Service & Timing Hair Dye Amount Calculator How many grams or ounces of color to mix for a root touch-up, regrowth or full head, by length and density.

Results are estimates built from the way colorists formulate at the bowl. Products differ by brand and hair differs by head, so always follow the manufacturer's instructions and strand test before a full application.