If you've ever wondered why one friend's hair soaks up a leave-in conditioner in seconds while yours barely absorbs anything, or why your hair takes forever to dry while someone else's air-dries in twenty minutes, the answer is porosity — and you can actually test for it at home in under five minutes.
Porosity is how well your hair's cuticle (the outer layer of each strand) lets moisture in and lets it out. That's it. It's not about how "healthy" your hair is — it's about the structure of the cuticle itself, and it changes how every single product you use behaves on your hair.
The float test
This is the fastest way to check.
Take one clean strand of hair — pulled from your brush or comb is fine, as long as it's product-free — and drop it into a glass of room-temperature water. Leave it alone for 2–4 minutes and watch what it does.
- Floats at the top → low porosity. The cuticle is tightly packed, so water struggles to get in.
- Sinks slowly, sits in the middle → normal/medium porosity.
- Sinks fast, straight to the bottom → high porosity. The cuticle is loose or raised, so water moves in quickly.
This works because porosity is essentially a density and absorption test — how much water your strand takes on determines whether it floats or sinks.
The spray bottle test
If you don't want to pull out a hair strand, this works on your whole head instead. Spritz a small section of dry hair with water and watch what happens.
- Water sits on top and beads up → low porosity. The cuticle is resisting the water rather than absorbing it.
- Water absorbs almost instantly → high porosity. The cuticle is open enough that moisture goes straight in.
What each porosity type actually means for your hair
Low porosity means the cuticle lies flat and tight. Moisture struggles to get in, but once it's in, it also struggles to get out — so low porosity hair tends to take a long time to get wet or dry, resists color and chemical treatments, and gets weighed down fast by heavy products that just sit on top of the cuticle instead of absorbing.
High porosity means the cuticle is raised or has gaps — sometimes from genetics, but more often from heat styling, coloring, bleaching, or chemical processing. Moisture gets in fast, but it also escapes just as fast, which is why high porosity hair often feels dry, frizzy, and prone to breakage no matter how much product goes on it — the hair can't hold onto what it absorbs.
Neither one is "bad" hair. They just need opposite strategies.
Why this matters more than most people realize
This is the part that trips people up: the same product can work great on one porosity type and completely fail on the other.
- Low porosity hair needs lightweight oils (like argan, jojoba, or squalane) applied with a little heat or on damp hair, because it takes real effort to get anything past that tight cuticle.
- High porosity hair needs the opposite — richer, more emollient ingredients and consistent protein or moisture support, because the cuticle lets moisture escape almost as fast as it goes in.
If you've ever felt like a product "didn't work" for your hair, there's a real chance it worked fine — it just wasn't matched to your porosity.
How our Hair Renewal Bundle supports both
We built the Hair Renewal Bundle around scalp health specifically because scalp condition matters regardless of which porosity you have — it's the one variable that affects both.
The bundle pairs our Repair Hair Oil, a pre-wash treatment built on argan oil with rosemary, nettle, and hibiscus, with our Restore Hydrating Scalp Tonic, a lightweight daily mist. Used together:
- Low porosity hair benefits from the oil's lighter argan base (applied before washing, with double shampooing to prevent any buildup) plus the tonic's daily hydration, which doesn't have the same absorption barrier the cuticle creates for heavier products.
- High porosity hair benefits from the same oil sealing in moisture right after it's absorbed, while the daily tonic replenishes hydration between washes — which matters more for high porosity hair since it loses moisture faster to begin with.
The oil is meant to be used 1–2 times a week before washing, and the tonic can be used daily on damp or dry hair to keep the scalp balanced in between — regardless of which porosity type you're working with, a healthy scalp is the starting point either way.
The bottom line
Run the float test or the spray test, figure out which side you land on, and stop guessing at products. Low porosity hair wants lightweight, penetrating ingredients used sparingly. High porosity hair wants richer, more sealing ingredients used consistently. And no matter which one you have, scalp health is the one thing that supports both.