Hair

How to find your hair porosity, and why it matters more than curl type

· 4 min read ·

Short answer

Hold a section of clean, product free hair under running water. If it takes a while to get properly wet and then dries slowly, you have low porosity. If it soaks through instantly and is dry again within an hour, you have high porosity. Ignore the glass of water float test, it is unreliable because shed hair carries oils and product that change how it behaves.

What porosity actually means

Porosity describes how easily water gets into your hair and how well it stays there. It is about the cuticle, the overlapping outer layer of the strand.

  • Low porosity: the cuticle lies flat and tight. Water struggles to get in, and once product is on there it tends to sit on the surface. You fight buildup.
  • High porosity: the cuticle is raised or damaged, often from colour, heat or chemical processing. Water rushes in and rushes straight back out. You are always dry.
  • Normal porosity: somewhere in between. You have options and most things work reasonably.

This is more useful than knowing whether you are 3C or 4A. Two people with identical curl patterns and opposite porosity need almost opposite products, which is exactly why the thing that transformed your friend's hair does nothing for yours.

The test that works

  1. Start with clean hair. No leave in, no oil, no dry shampoo.
  2. Hold a section under running water.
  3. Watch how long it takes to be properly saturated, not just wet on the outside.
  4. Then note how long it takes to air dry.

Slow to wet and slow to dry means low porosity. Instantly soaked and quick to dry means high. If you are somewhere in the middle, you are normal porosity and you have an easier time than most.

Skip the float test. Dropping a shed hair in a glass of water is the most repeated porosity test online and it is close to useless. Whether a strand floats depends mostly on surface oils, product residue and how you dropped it in, not on your cuticle.

What to buy for low porosity hair

Your enemy is buildup, and your problem is getting anything to absorb at all.

  • Lightweight formulas. Skip heavy butters, thick creams and most oils.
  • Use warm water when washing, which helps lift the cuticle enough to let moisture in.
  • Apply product to soaking wet hair, not damp. The water is the moisture.
  • Clarify regularly, roughly every two to four weeks, or everything stops working.
  • Be cautious with protein. Low porosity hair often does not need it and goes stiff.

SheaMoisture makes a Low Porosity Baobab and Tea Tree line specifically for this, and it is one of the most useful and least known products in their range.

What to buy for high porosity hair

Your problem is not getting moisture in, it is keeping it there.

  • Layer. Leave in, then cream, then an oil or butter on top to seal.
  • Richer products work here in a way they would suffocate low porosity hair.
  • Protein helps, because high porosity usually means some structural damage. Alternate protein and moisture treatments.
  • Look for the words sealing, high porosity, or bond repair on the label.

SheaMoisture High Porosity Moisture Seal is the obvious drugstore option. If your high porosity comes from bleach or relaxer, a bond repair treatment such as Olaplex No. 3 is worth adding weekly.

How porosity changes

It is not fixed for life. Colour, bleach, relaxers, flat irons and even hard water raise the cuticle over time, which pushes hair towards high porosity. Trimming off damaged length brings you back.

It can also vary along a single strand. Roots are often lower porosity than ends, because the ends are older and have been through more. If your ends drink product and your roots get greasy, that is why, and it is normal.

Get products matched to your porosity

Questions people also ask

How do I test my hair porosity at home?

Hold clean, product free hair under running water. Slow to wet and slow to dry means low porosity. Instantly soaked and fast to dry means high porosity. This is more reliable than the float test.

Is the float test for hair porosity accurate?

No. Whether a shed strand floats depends mostly on surface oils and product residue rather than your cuticle, so results vary wildly. The running water test is far more reliable.

Can hair porosity change over time?

Yes. Colour, bleach, relaxers, heat styling and hard water all raise the cuticle and push hair towards high porosity. Porosity also varies along a strand, with ends usually more porous than roots.

Is low or high porosity hair better?

Neither. They are different, not better or worse. Low porosity resists moisture but holds it once it is in. High porosity absorbs easily but loses it fast. Each needs a different product weight.

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