Hair Porosity in Brief: The Float Test and What It Misses

Direct answer: A scalp scrub removes buildup, flakes, and styling residue that shampoo alone can miss. Used occasionally and gently, it leaves the scalp feeling cleaner without needing a full clarifying routine.

A scalp scrub removes buildup, flakes, and styling residue that shampoo alone can miss. Used occasionally and gently, it leaves the scalp feeling cleaner without needing a full clarifying routine.

This guide walks through scalp scrubs in brief in plain steps, with the trade offs stated honestly and a short list of checks you can run yourself. Nothing here needs special equipment or a professional call out to get started, and each section ends with the decision that actually matters.

In brief: clarifying shampoo is a strong cleanser that removes product buildup, mineral deposits, and excess oil that regular shampoo leaves behind. Most people need it every few weeks, not weekly. Follow it with conditioner, and use it before colour or deep treatments.

Leave in conditioner adds light moisture, slip for detangling, and a layer of protection against heat and friction, without the weight of a rinse out product. Fine hair needs a spray and a small amount. Thick, dry, or curly hair usually benefits most.

Use a clarifying shampoo when hair feels coated, flat, or resistant to products that used to work: that is mineral, product, and sebum build up, and a stronger surfactant wash removes it. For most people that means somewhere between once a month and once a week. Used as a daily shampoo it strips colour and moisture faster than hair can afford.

Use enough to coat the mid lengths and ends so the hair feels slippery and detangles under your fingers, usually a grape to a walnut sized amount depending on length and density, and keep it off the scalp unless the scalp itself is dry. Conditioner works on the surface in the time it takes to wash the rest of you: cationic ingredients deposit where hair is damaged and reduce friction. Leaving it on for half an hour adds almost nothing.

Porosity is how easily your hair absorbs and loses water, set by the state of the cuticle, and it guides product weight better than any other single idea in hair care. Ignore the float test: strand thickness and surface tension decide whether hair floats, not porosity. Judge instead by behaviour: how fast your hair gets fully wet, how long it takes to dry, and how quickly products seem to vanish or sit on top. Those three observations sort most hair correctly in a week.

Why the float test fails

The ritual is famous: drop a clean strand in water, floating means low porosity, sinking means high. It fails on physics. A fine strand with a healthy, intact cuticle can sink because it is thin, and a coarse strand full of damage can float on surface tension and trapped air. Residue on the strand changes the result again, which is why the same person gets different answers on different days and quietly stops trusting the whole concept.

Porosity itself is real; the test is the problem. Hair science measures it with dye uptake, protein loss, and wetting behaviour under controlled conditions. Your bathroom version of those is observation over time, which is slower and much more accurate than one strand in a glass.

The three observations that work

First, wetting: under the shower, does water bead and run off for a while before the hair feels truly saturated, or does it soak in at once? Slow wetting signals a tight, low porosity cuticle. Second, drying: hair that takes many hours to air dry is holding water it absorbed, while hair dry in an hour either absorbed little or loses it fast, and the wetting test separates those two. Third, product behaviour: oils and creams sitting glossy on the surface by evening suggest low porosity; products disappearing as if the hair drank them suggest the opposite.

Write the three answers down once. Together they place you on the spectrum well enough to shop by, and they catch the mixed cases the float test flattens, like porous ends on otherwise low porosity hair, which is extremely common on long hair because the ends are years older than the roots.

What each type should actually do differently

Low porosity hair wants warmth and lightness: warm water and a warm towel help products in, water based and lighter products beat heavy butters that just laminate the surface, and clarifying matters because buildup accumulates on a cuticle that already resists entry. High porosity hair, often from bleaching, heat, or age, wants sealing and protein support: richer products, layering a cream under an oil, and gentle handling since the raised cuticle snags and breaks.

Medium porosity is the forgiving middle and needs the least strategy, which is worth saying in a niche that profits from everyone believing their hair is a special case. Most routines fail not because the porosity plan was wrong but because the plan kept changing every wash. Pick the routine your observations support and run it a month.

Damage changes porosity, so retest by behaviour yearly

Porosity is not a fixed identity. Bleach, relaxers, years of heat, and simple age raise it, and growing out damage lowers it again at the roots first, which is why long hair so often needs two product weights at once: light at the roots, rich at the ends. Treat the three observations as a yearly check rather than a personality type, and let the hair in front of you, this year, set the routine.

Keep reading: Washing Hair After Workouts: Sweat, Salt and Scalp Rules, Scalp Sunscreen: Protecting Your Part and Hairline Without Greasy Hair, and How to Read a Shampoo Label in Thirty Seconds cover the nearby cases in this series.

Frequently asked questions

Is the float test an accurate way to measure hair porosity?

No. Strand thickness, surface tension, and product residue decide floating more than cuticle condition does, so the same hair can give different results day to day. Behaviour over several washes is a better guide.

How can I tell if my hair is low porosity?

Water beads and takes time to saturate it in the shower, products tend to sit on the surface, and buildup accumulates easily. Warm water and lightweight, water based products usually work better than heavy butters.

What does high porosity hair need?

Sealing and support: richer products, layering cream under oil, and gentle handling, since a raised cuticle loses moisture fast and snags. High porosity usually comes from bleach, heat, chemical services, or age.

Can porosity change over time?

Yes. Chemical services and heat raise it, and growing out damage lowers it again starting at the roots. Recheck by behaviour each year, since long hair often needs lighter products at the roots and richer ones at the ends.