Does the Hair Porosity Float Test Work?

Researched and written by Curl Centric. Read by an AI voice.

A strand in a glass of water can't tell you your porosity. We explain why, and what your wash day can tell you instead.

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The full guide, with every source: Hair porosity.

Transcript

This is Curl Science by Curl Centric.

Your hair's true porosity can't be measured accurately at home. Not with a glass of water and not by running your fingers up a strand. Those tests respond to real things. They just can't isolate porosity. Here's what they actually pick up and the two things you can check instead.

Start with what porosity is. Your hair has an outer layer called the cuticle, made of tiny overlapping scales, a bit like shingles on a roof. Porosity describes the tiny spaces within your hair and affects how readily the strand takes up water. High porosity often reflects damage that has built up over time. Low porosity usually isn't damage at all. It's often just how your hair grew.

Now the float test. You take a clean strand from your comb, drop it into a glass of water, and watch whether it sinks. But the result depends on a mix of surface tension, the strand's density, its natural oils, and whatever product is still sitting on it.

In one careful demonstration, untreated and oiled strands floated, while conditioner made some strands sink more easily. Whether the hair was pushed beneath the surface also changed what happened. The product and the test setup helped decide the result.

That's also why you can get a different answer on a different day. The test is heavily influenced by what's sitting on the outside of your strand, and that changes every wash day.

The strand test has the same problem from the other direction. You slide your fingers up a strand and feel for snags. But the edges of your cuticle scales are microscopic. Your fingers can feel roughness, residue, or serious damage, but they can't measure the pores inside your hair.

While we're here, the cuticle doesn't open and close like a door on a hinge. Its scales can swell, lift, chip, or wear away, but you can't measure those changes with your fingers. Researchers need laboratory instruments to see them properly.

The spray test, where you mist your hair and watch whether the water beads up or soaks in, mostly reads how easily the surface gets wet. Oils, product residue, and how closely your strands sit together can all change the result. That tells you something about how your hair is behaving that day, but it still isn't a direct porosity measurement.

So how is porosity actually measured? Researchers can use laboratory methods such as gas sorption to measure pore volume, pore size, and the accessible surface area inside damaged hair. There's no home version of that equipment, and no test you can do in your bathroom gives you the same measurement.

Which means it's worth changing the question. Instead of asking for an exact porosity label, ask how much your hair has been through and how it behaves. You can answer both of those, and together they tell you most of what you wanted the label to tell you anyway.

Your hair's history does much of the work. A lot of high porosity comes from cuticle damage adding up, and you already know what your hair has been through. Bleach, permanent color, relaxers, repeated high heat, sunlight, and years of rough combing can all increase porosity. They just don't increase it equally.

Here's the number worth remembering. Under the conditions used in one laboratory study, a single minute of bleaching nearly tripled the accessible pore surface area of a strand. After about 10 minutes, the measured surface area dropped again. That sounds like good news, but it wasn't. The researchers concluded that smaller pores had broken down and merged into larger ones.

How your hair behaves fills in the rest. The evidence for sorting your hair into porosity groups this way is weaker, and we'll say so. But timing can still give you a useful clue because you can watch how quickly your hair gets wet and how long it takes to dry.

Hair that takes a long time to get wet and a long time to dry may be behaving like low porosity hair. Hair that gets wet and dries quickly may be behaving more like high porosity hair. But your density, strand thickness, length, products, and even the weather can change both times. Treat timing as a signal, not a verdict.

A lot of people land somewhere in the middle, and medium porosity gets very little airtime. There isn't a clean cutoff between the porosity types, and there isn't a home test that finds one.

In everyday terms, if water gets into your hair at a reasonable rate, your conditioner works roughly the way the bottle says it should, and your color takes evenly, your hair may be behaving somewhere in the middle.

Those two answers, your hair's history and its everyday behavior, help decide the things you wanted the label for. Which products to reach for. Whether a protein treatment may help. And whether gentle warmth is worth trying with your deep conditioner.

Here's roughly how that works. If your hair behaves like low porosity hair, lightweight products may be less likely to build up on the surface. Gentle warmth may also help some conditioners spread and work more effectively, but it doesn't permanently open your cuticle.

If your hair behaves like high porosity hair, richer creams may help slow moisture loss. A treatment containing hydrolyzed protein may also make damaged strands feel stronger or smoother for a while.

One last thing, and it changes what you do on wash day. A cuticle that has been chipped, broken, or worn away doesn't grow back. Hydrolyzed proteins and conditioning ingredients can temporarily coat damaged areas and improve how your hair feels, but those effects wash away.

So the real lever isn't permanently repairing hair that's already porous. It's limiting the damage you add from here. Repeated lightening, excessive heat, and rough detangling can all cause more damage that your strand can't heal.

We built a quiz that works this way. It's nine questions, takes about 90 seconds, and doesn't require an email. It weighs your processing and damage history more heavily than one-time feeling tests because that part has stronger research behind it.

At the end, it also tells you which answers it ignored and why. It's at curlcentric.com/hair-porosity-test, and the link is in the show notes.

That's it for this episode. If it helped, follow Curl Science in your podcast app so the next one reaches you, and leave us a rating while you're there. Curl Science is researched and written by the Curl Centric team, and it's read by an AI voice.