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Hair Porosity Test: Low, Medium or High?

Eight questions, including the float test and the finger-slide test, and you get your porosity with a wash-day routine, the ingredients that work on it, and the ones that will sit on top doing nothing.

Built by Maya Brooks, reviewed by Hazel Casey

Two people can buy the same conditioner and get opposite results. Porosity is why. Porosity means how open the outer layer of your hair is. It decides how fast water gets in, and how fast it leaves. Guess wrong and your hair feels greasy and dry at once. Or it drinks a whole bottle of product and still frizzes by lunch.

This test asks eight questions. It includes the float test and the slide test, and it weighs them together instead of trusting one. You get low, medium or high porosity. You also get a wash-day routine, the ingredients to reach for, and the ones to skip.

What hair porosity actually is

Every strand has an outer layer called the cuticle. It is made of tiny scales that overlap like roof tiles. When those scales lie flat and tight, water struggles to get past them. That is low porosity. When they are lifted or damaged, water moves in and out freely. That is high porosity. Medium sits between the two and is the easiest to live with.

Part of your porosity comes from your genes. Part of it you earn. Some people are born with a tightly packed cuticle. Most people move toward high porosity over time. Bleach, box dye, flat irons and hot water all push it that way. That is why the same head of hair can be low porosity at the roots and high porosity at the ends, where the damage has built up.

Hair porosity float test infographic showing three glasses of water: a strand floating on top for low porosity, hovering in the middle for medium porosity and sunk to the bottom for high porosity, with magnified cuticle diagrams and what each porosity type needs, from lightweight milks to protein treatments and oils. — The hair porosity float test: where a clean strand settles in water hints at low, medium or high porosity.

The three tests, done properly

The float test. Take a strand that has shed naturally, drop it in a glass of room-temperature water, and wait four minutes. Floating means low porosity, mid-glass means medium, and sinking means high. The catch is that it only works on clean hair. Any product, oil or dry shampoo coats the strand and makes it float. That is how so many people decide they are low porosity when they are not.

The spray test. Mist plain water onto a dry section. Water that beads and rolls off is meeting a closed cuticle. Water that vanishes on contact is being pulled straight in. This one is quicker than the float test and harder to get wrong.

The slide test. Hold a strand at the end and run your fingers up toward your scalp. Smooth and slippery is a flat cuticle. Bumpy, rough or catchy means the scales are raised. Do this on the mid-lengths, not the very ends, which are damaged on almost everyone.

Two drying clues matter just as much. One is how long your hair takes to air dry. The other is how it acts in humid air. Hair that stays wet for hours is holding water behind a closed cuticle. Hair that dries in forty minutes and frizzes right away is holding nothing.

How to treat each porosity type

Low porosity. Your problem is getting moisture in, not keeping it. Warmth is the key: apply your mask to damp hair, add a cap, and give it ten minutes. Keep products light and watery. Use a clarifying shampoo often so build-up does not block them. Go easy on protein, since low porosity hair rarely needs it.

Medium porosity. Switch between protein and moisture masks. Condition every wash and use heat protectant. This type turns into high porosity more often than any other, so your job is upkeep, not repair.

High porosity. Your problem is keeping moisture in. Layer it: liquid first, then an oil to seal, then a cream on top. Use cooler rinses, sleep on satin, and pair every protein treatment with a moisturizing mask so your hair does not go brittle.

High porosity hair: signs, causes and the best routine

High porosity hair has gaps and lifted areas in its outer layer, the cuticle. Water and products rush in fast, but they leave just as fast, so the hair feels dry again a few hours after you style it.

Signs of high porosity hair

It dries very quickly after washing, sometimes in under an hour.
It drinks up leave-in and oil, then feels rough or straw-like again by the next day.
It frizzes in humid weather and tangles easily.
Color fades fast, and the ends look dull or split.

What causes it

Most high porosity hair is damaged hair: bleach, permanent color, relaxers, perms, frequent flat ironing, sun, chlorine and rough brushing all lift the cuticle. Some curly and coily hair is also naturally more porous at the ends, because the bends in each strand leave the cuticle more exposed.

A routine that works for high porosity hair

Wash gently with a sulfate-free shampoo and rinse in cool water.
Use protein, then moisture. A protein treatment every 2 to 4 weeks fills gaps in the cuticle. Always follow it with a moisturizing mask so your hair does not turn brittle. Our protein or moisture quiz tells you which one you need first.
Layer and seal. Use the LOC or LCO method: a water-based leave-in, then an oil and a cream (or the cream before the oil) to lock the moisture in.
Cut the heat. Air-dry when you can, and always use a heat protectant when you cannot.
Protect at night with a satin pillowcase or bonnet.

Look for ingredients like hydrolyzed proteins (keratin, wheat, rice), shea or mango butter, and heavier sealing oils such as castor or olive oil.

Low porosity hair: signs and the best routine

Low porosity hair has a tightly closed cuticle. It is often healthy and shiny, but water and products struggle to get in, so they sit on top and build up.

Signs: water beads on the strands, hair takes a long time to dry, products leave a film or feel greasy, and color takes longer to process.
Routine: apply conditioner and masks with gentle heat (a warm towel or a shower cap), choose light, water-based products with humectants like glycerin or aloe, clarify every couple of weeks, and skip heavy butters.

Porosity is only part of the picture. Pair it with your curl pattern from the hair type quiz to choose products that fit both.

Three myths worth dropping

“The float test is the final word.” It is one clue. Clean hair, room-temperature water and four minutes give you a decent signal; anything else gives you a coin flip. That is why this test weighs eight answers instead of one.

“Low porosity means healthy hair.” Porosity is not a grade. Low porosity hair can be perfectly healthy and still look dull because products are sitting on the surface.

“You can change your porosity for good.” You can close a raised cuticle for a few days with cool rinses and protein. You can also stop more damage. But you cannot rebuild a cuticle that bleach has worn away. Those ends have to grow out.

Frequently Asked Questions

What is a hair porosity test? −

It is a set of checks that show how easily your hair takes in water and how long it holds it. The float test, the spray test and the finger-slide test are the common ones, and together they place you at low, medium or high porosity.

How do I test hair porosity at home? −

Drop one clean shed strand into a glass of room-temperature water and wait four minutes. Floating means low porosity, mid-glass means medium, sinking means high. Back it up by spraying water on dry hair and watching whether it beads or absorbs.

Is the float test accurate? −

Only as one clue among several. Product, oil or dry shampoo on the strand makes it float regardless of porosity, which is the most common reason people get a wrong result. Use clean hair and combine it with the spray and slide tests.

What does low porosity hair need? −

Warmth and light products. Apply conditioner to damp hair with a cap for ten minutes, use watery leave-ins rather than heavy butters, clarify every few weeks to clear build-up, and keep protein treatments occasional.

What does high porosity hair need? −

Sealing. Apply liquid, then oil, then cream on damp hair, rinse with cool water, deep condition weekly and use protein often, always followed by a moisturizing mask so the hair does not turn brittle.

Can hair porosity change? −

Yes, in one direction easily. Bleach, box dye and heat raise the cuticle and push hair toward high porosity. You can smooth a raised cuticle for a while with cool rinses and protein, but damaged ends only truly leave when they are cut off.

Keep going: once you know your porosity, pick a cut that works with it in our thin hair guide or coily hairstyles, and find your color season with the color analysis quiz.