Hair Porosity Test: What It Means and Why the FloatTest Fails

Hair porosity describes how easily your hair absorbs and holds on to water. The best way to test it at home is to watch how your hair behaves when it gets wet and dries. Hair that takes a long time to soak and dry is likely low porosity. Hair that soaks up water quickly and dries fast is likely high porosity. The popular test of dropping a strand in a glass of water is not reliable, for reasons explained below.

What porosity actually means

Each hair strand has an outer layer called the cuticle, made of overlapping cells a bit like roof shingles. When the cuticle lies flat, water has a harder time getting in and out. When it is lifted or damaged, water passes through more easily.

So porosity is mostly a description of your cuticle’s condition. It is partly genetic, but it can also be changed by bleach, chemical treatments, heat, and sun, which is why the ends of your hair are often more porous than the roots. They have been exposed to more for much longer.

Why the float test is unreliable

You have probably seen this test: drop a clean strand into a glass of water and wait. If it floats, you have low porosity. If it sinks, you have high porosity.

It sounds scientific, but several things other than porosity can affect the result:

• Oils and product residue can help a strand float.
• Surface tension can hold up even a porous strand.
• The way you drop it and the shape of the strand can change whether it breaks the surface.
• A single hair does not tell you much, since porosity can vary across your head and along each strand.

Run the test twice and you may get two different answers. It is harmless to try, but do not choose your whole routine based on it.

Better ways to test your porosity

Use several of these signs together. No single sign is conclusive.

Watch it in the shower. Does water bead up and roll off at first, or does your hair get soaked straight away? Slow soaking suggests low porosity.

Time your drying. Hair that takes hours to air-dry is often low porosity. Hair that dries very quickly, especially if it feels dry afterward, is often high porosity.

Notice how products behave. Low porosity hair often has products sitting on top, leaving it greasy or coated. High porosity hair seems to drink up products, then feel dry again shortly after.

Run your fingers along a strand. Slide up a strand toward the scalp. If it feels smooth, the cuticle is probably flat. If it feels rough or bumpy, the cuticle may be raised. This is a little subjective, but it can help.

Think about your hair’s history. If it has been bleached or heat styled a lot, the treated sections are probably high porosity, whatever the untreated roots are doing.

Ask a professional. A stylist can feel your hair and ask about its history. They will often give you a better answer than any at-home test.

Signs of each type

	Low porosity	Medium porosity	High porosity
Getting wet	Slow, water beads up	Normal	Very fast
Drying	Slow	Moderate	Fast
Products	Sit on the surface	Absorb well	Absorb and vanish
Common issues	Buildup, limpness	Few	Frizz, dryness, tangles
Color	Takes longer to process	Takes evenly	Takes fast, but fades fast

Caring for low porosity hair

Low porosity hair holds on to moisture well once it gets in, but getting it in is the problem. Buildup is the most common complaint.

• Use lightweight products. Light leave-ins and water-based products tend to work best.
• Apply products to damp, warm hair. Warmth can help products absorb better.
• Clarify now and then. A clarifying shampoo every few weeks removes product buildup.
• Use deep conditioner with mild heat. A warm towel or a heat cap helps it work.
• Go easy on heavy butters and oils, which are likely to sit on top of the hair.

Caring for medium porosity hair

Medium porosity hair is the easiest to manage. It accepts products well, holds styles, and takes color evenly.

• Stick to a simple routine. A shampoo, conditioner, and an occasional mask are usually enough.
• Protect what you have. Use a heat protectant and be careful with chemical treatments, so that it stays this way.

Caring for high porosity hair

High porosity hair absorbs moisture easily but loses it just as quickly. It is often also fragile, particularly if the porosity comes from damage.

• Condition every time. Rinse-out and leave-in conditioners both help to reduce friction.
• Seal in moisture. Apply a light oil or cream to damp hair, particularly on the ends.
• Try protein treatments. Hydrolyzed proteins can temporarily strengthen weak spots. Use them as directed, as too much protein can make hair feel stiff.
• Limit damage. Reduce bleach and hot tools, use a heat protectant, and protect your hair from the sun.
• Rinse with cooler water. Many people find that this helps cut down on frizz, though the effect is modest.
• Trim damaged ends. Damage does not heal. Regular trims remove the worst of it and help keep the rest looking healthy.

Porosity vs. hair type

Porosity is separate from curl pattern. Any hair type can be low or high porosity, although curlier hair often tends to be drier, since scalp oils have a harder time traveling along a curled strand. Knowing both your porosity and your curl pattern helps you choose products. If you are not sure of your pattern, see our hair type chart.

What porosity means for your next cut and color

Porosity also affects what happens at the salon, so mention it at your next appointment.

Color. Low porosity hair can resist color and take longer to process. High porosity hair can take color quickly and fade fast, and it can process unevenly from root to tip. See balayage vs. highlights for more on color choices, and hair color trends for ideas.

Cut. High porosity ends often look frizzy or see-through, which can make a cut seem unhealthy, no matter how good the shape is. Cutting off an inch or two can make a big difference, and it may matter more than a new product.

Styling. Low porosity hair tends to hold a straight style in humid weather better, while high porosity hair can frizz sooner. Ask your stylist about which cuts work with what your hair already does.

Related guides

• The Curly Girl Method: A Simple Beginner’s Guide

See what a fresh cut could look like

If your ends are damaged, a shorter cut could be the quickest way to healthier-looking hair, but it can be hard to imagine the change. Hairover lets you upload a clear photo, get a hair analysis, and try hairstyles on your own face in Style Studio. Try the shorter length before you decide how much to cut.

Preview shorter cuts on your own photo with Hairover.