General information only. ShampooGarage articles are educational and are not medical or individualized hair, scalp, or skin advice.
Conditioner sits on your hair like lotion on a raincoat, or it sinks in and the lengths feel dry again before the hair is fully dry. Friends with the same curl pattern are no help, because curl shape and porosity are different facts. Porosity is how easily water and ingredients pass through the cuticle. Get that wrong and you will keep buying the right brand for the wrong reason.
The cuticle, without the float test
Each strand is wrapped in cuticle, flattened cells overlapped like roof shingles. When the shingles lie tight, water beads and products sit on top. That is low porosity. When they are slightly lifted, water and conditioner move in and stay reasonably well. That is medium porosity. When they are chipped or stuck open, from bleach, relaxers, heat, or sometimes from the way the hair grew, water rushes in and leaves just as fast. That is high porosity.
The glass-of-water float test — drop a clean hair in and see if it sinks — is a poor way to sort these. A little oil, leftover product, a short piece, or the surface tension of the water can hold a strand up or drag it down. You learn almost nothing about the cuticle and a lot about how you prepared the sample.
Observations that track the cuticle better
Wet-out time. In the shower, low-porosity hair takes a long time to feel truly wet and a long time to dry. High-porosity hair darkens with water immediately and air-dries fast, often with the ends dry while you are still getting dressed.
Product behavior. If creams stay visible on the surface and the hair looks dull by the next day, suspect low porosity or simple buildup. If you moisturize and the lengths feel parched again the same afternoon, suspect high porosity. Medium porosity usually accepts a normal rinse-out and does not need a special ritual.
The slide. Pinch a shed strand and slide your fingers from the tip toward the root, against the cuticle. A smooth slide suggests a tighter cuticle. A rough, bumpy slide suggests lifted tiles. Ends are often rougher than roots on the same head.
History. Virgin hair can be low porosity. Several rounds of bleach, a relaxer, or daily high heat push porosity up over time. Roots can be low while the last four inches are high. Treat those zones differently instead of averaging them into one product.
What to put on each type
| Low porosity | Medium porosity | High porosity | |
|---|---|---|---|
| The annoyance | Product sits on top; hair takes forever to get wet | Keeping a simple routine consistent | Moisture leaves; hair feels rough and fragile |
| Formulas that cooperate | Lightweight liquids, humectants, a clarifying wash on a schedule | Most balanced shampoos and conditioners | Creams and butters on the lengths, occasional protein, a seal on top |
| Formulas that fight you | Thick butters every wash, heavy non-soluble silicones | Stacking five stylers "just in case" | Watery sprays used alone with no cream or oil after |
| Useful habit | Apply to damp hair; warm a conditioner briefly; clarify when film builds | Condition the lengths, shampoo the scalp | Leave-in, then cream, then a little oil on the ends; less heat |
Low porosity, in practice
Warmth helps a conditioner spread. A few minutes under a shower cap with the warm steam of the bathroom is enough. You do not need a heating gadget. Clarify when the hair looks coated even after a gentle wash. How often that reset belongs is in the clarifying guide. Lighter oils — the kind that do not sit in a paste — are easier to live with than a heavy butter on the roots. If the tap is hard, mineral film mimics low porosity because everything sits on the surface. Check the hard-water guide before you decide your cuticle is "closed" forever.
High porosity, in practice
Water gets in easily, which is why this hair feels soaked in the shower and dry on the way to work. Layer a leave-in on damp lengths, then a cream if the hair is curly or coarse, then a small amount of oil or butter on the ends only. That order is sometimes called LOC (liquid, oil, cream) or LCO (liquid, cream, oil). The letters matter less than the idea: put water-based moisture on first, then something that slows it from leaving. The leave-in guide covers how much leave-in is too much.
Protein can temporarily fill gaps in a rough cuticle. If wet hair stretches and feels gummy, read the protein guide before you add another butter. Protein on hair that is already stiff will make it snap.
SheaMoisture Coconut and Hibiscus Curl Enhancing Smoothie is an example of a heavier cream styler. On high-porosity curls it can sit in the "cream" step. On fine or low-porosity hair the same jar is often too much, and the hair goes flat. The product did not change. The cuticle did.
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SheaMoisture Coconut and Hibiscus Curl Enhancing Smoothie jar
Shampoo, matched to porosity
Low-porosity hair fogs up with leftover styler. A gentle daily wash plus an occasional clearer shampoo keeps the surface available. High-porosity hair does not need a strong detergent every day. A milder cleanser, including many sulfate-free options, is usually more comfortable, followed at once by conditioner. The tradeoff is explained in the sulfate-free article. Shampoo still belongs on the scalp. The ends get the runoff and the conditioner.
What porosity does not tell you
It does not pick your curl type, your scalp oil, or whether you have dandruff. An oily scalp can sit on low-porosity lengths. A dry, flaky scalp can sit on high-porosity bleached ends. Scalp choice is separate: the scalp-type guide.
Roots and ends on the same head
A lot of heads are two porosities. The roots grew in after the last round of color, so they resist product and take forever to dry. The ends were bleached or ironed, so they drink conditioner and still feel rough. One cream all over will smother the roots and underfeed the ends.
Shampoo the scalp as its own skin type. Put the richer conditioner from the mid-lengths down. If you use an oil, keep it on the last few inches. When you diffuse or blow-dry, the ends may be finished while the roots are still cool and damp. Stop heating the ends. Let the roots finish on a lower setting or in the air. Cutting the ends does not lower the porosity of what is left if you keep bleaching, but it does remove the most beaten-up fiber, which is why a trim can make the whole style feel easier even though porosity is not a haircut.
Skip the quiz. In one shower, notice how fast the hair got wet, whether yesterday's cream is still sitting there, and whether the ends have been bleached. Those three answers pick the weight of the next conditioner.
On your next wash, did the hair resist water, drink it and stay soft, or drink it and dry rough before you left the house?