I said this on Instagram but I want to elaborate. Everyone is talking about porosity right now. Is your hair low porosity or high porosity. These things matter a little. But I think we are all looking at the wrong thing first. Two things run your whole hair routine and almost nobody talks about them. Your density. And how thick each single strand is.
What density means
Density is how many strands of hair you have on your scalp. It has nothing to do with how thick each strand is. You could have thousands of thin strands packed close together, or fewer strands that are each thick. Your hair would look and act very differently depending on which one you have. Most people have somewhere between 100,000 and 150,000 hairs on their scalp. This changes a bit by natural hair colour and by person.
What strand width means
Strand width is a different thing. It is how thin or thick one single strand is. Fine strands are on the thinner side. Thicker strands are wider and stronger. I have fine strands and medium density myself. That is one reason I do not do braids very often. My fine strands cannot handle the pulling and tension the way thicker strands can.
Strand width is not just how your hair feels either. Thinner strands usually have fewer layers of the protective outer coating, called the cuticle. Thicker strands usually have more layers of cuticle plus more of the inner core that gives hair its strength. This is why thicker strands tend to resist breaking better than fine ones, even when both have the exact same porosity.
Why this matters more than porosity day to day
Density decides how much product you actually need. A head with high density has more strands all needing a share of the same amount of oil or cream. If you copy a routine made for low density hair, your hair will feel underfed no matter how correct your porosity steps are.The bit nobody tells you about porosity
Porosity is not one fixed number for your whole head either. New growth near your scalp has not been through months of sun, heat, and styling, so it tends to be lower porosity. Your ends are the oldest part of your hair and have usually been through the most damage, so they often test higher. A product sold to you as being for low porosity hair or high porosity hair is really only talking about part of your head.
There is also no truly accurate way to test this at home. The float test, where you drop a strand of hair into a glass of water, is seen as unreliable by hair scientists and trichologists. Oil, product build-up, water temperature, and even strand width can all change the result. Real porosity testing needs lab equipment. At home, you can only make a smart guess. Hair that has never been coloured or heat styled tends to run lower porosity. Hair that has been bleached, relaxed, or styled with a lot of heat tends to run higher, because those processes rough up the cuticle.
This is why I think building your whole routine around a label you cannot even measure properly makes less sense than paying attention to two things you can actually see and measure on your own hair right now.
What to actually do about it
For density, try the scalp test. Part your hair in a few different spots, at the crown, the sides, and the back, in good light. If you can see your scalp easily without moving your hair, you likely have low to medium density. If your scalp is hard to see even when you part it, you likely have medium to high density. This works better for Afro textured hair than the ponytail test, which was built around straighter hair types and does not translate the same way once you add shrinkage and curl pattern into the mix.
For strand width, take one clean, dry strand and lay it across a sheet of paper. If you can barely see it, it is fine. If it is easy to see and feels sturdy, it is on the thicker side. Somewhere in between is medium.
Once you know both, change two things. How much product you use. And how gently or firmly you handle your hair every day. That will do more for your wash day than any porosity chart ever will.
