Hair typing describes the shape of your curl. Porosity describes how readily your hair takes up and loses water. Neither is a precise measurement, but porosity is the more useful idea for choosing products, because it points at the condition of the hair surface rather than at how the hair looks.
What hair typing tells you, and what it leaves out
The familiar scale of types 1 to 4, with subtypes A to C (so 3A is a loose curl and 4C a tight coil), was created in the 1990s by the stylist Andre Walker and was originally intended to market his own hair-care line. It was not built as a scientific classification. It has been criticised for an implied hierarchy that favours looser patterns, and for ignoring density and the fact that one head often carries several patterns.
That last point matters. Many people have tighter coils at the nape, looser curls at the crown and a different texture again where hair has been coloured or heat styled. Use a type as shorthand for finding styling ideas and photographs of similar hair. Do not treat it as a rule for what your hair needs.
| Trait | What it affects | Does typing capture it? |
|---|---|---|
| Curl pattern | Shape, shrinkage, how a style holds | Roughly |
| Strand thickness (fine, medium, coarse) | How heavy a product feels | No |
| Density (number of strands) | Coverage, how much product you need | No |
| Surface condition and porosity | How hair wets, dries and holds product | No |
| Scalp oiliness | How often you need to wash | No |
What porosity means
Each strand is wrapped in a cuticle of overlapping scales, a little like roof tiles. In healthy hair the scales lie flat and the surface carries a thin fatty layer, which makes it water-repellent. Chemical treatment, heat, friction and sunlight gradually strip that layer and lift or crack the scales, so the surface becomes more water-attracting and rougher. This wear builds from root to tip, which is why the ends of a long head of hair are the most weathered.
In everyday use, people describe two ends of a scale:
- Lower porosity: the surface is intact. Hair can resist getting wet at first, products may sit on top and feel heavy, and drying can be slow.
- Higher porosity: the surface is worn or uneven, whether by styling or by nature. Hair wets quickly, dries quickly and often feels rough or frizzy.
These are community descriptions rather than clinical categories, and most hair sits somewhere between. Roots usually behave more like the lower end and ends more like the higher end, because the ends are years older than the new growth at the scalp.
Home tests and how far to trust them
The float test, where a clean strand is dropped in a glass of water and a sinking strand is read as high porosity, is the best known. Cosmetic chemist Michelle Wong argues that it does not measure porosity at all. A strand floats or sinks largely because of surface tension, and damaged hair sinks because its worn surface attracts water, while oils and conditioner residue can make any strand float. The same applies to the water-droplet test. In her view these tests detect surface damage, which is still useful information, but the label "porosity" can mislead.
Watch your own hair. Note how quickly it wets in the shower, how long it takes to dry, and how a product feels the day after you use it. Wong's suggestion for professionals is to try a product on a strand of the person's actual hair, and the same logic works at home: test, then judge the result.
If you do try a float or slip test, start with clean hair that has no oils, silicones or stylers on it, and treat the result as a conversation starter rather than a diagnosis. Running a finger up a strand from the tip towards the root is a quick check too: a rough, catching feeling suggests lifted scales, though this is informal and unvalidated.
Turning the observations into a routine
| What you notice | Likely explanation | What to try |
|---|---|---|
| Water beads up, hair is slow to wet, products feel heavy | Intact surface, or a film of product | Lighter formulas, use on soaking wet hair, clarify occasionally to remove build-up |
| Wets and dries fast, feels rough, frizzes easily | Worn cuticle | Richer conditioner and leave-in, less heat, less friction, trim damaged ends |
| Roots and ends behave differently | Normal weathering | Treat the ends as damaged and the roots lightly |
Conditioners work largely by reducing friction between strands and smoothing the surface, which is why they help most on rougher, more worn hair. For more on picking formulas see how to choose curly hair products, and for what to do when hair feels either limp or brittle see moisture vs protein balance.
When a change in texture needs a professional
Curl pattern can loosen after heat or chemical damage, and it can also shift with hormones, medication or illness. The American Academy of Dermatology advises seeing a board-certified dermatologist at the first sign of changes in hair texture or appearance, and the NHS notes that shedding 50 to 100 hairs a day is normal. If your hair suddenly feels different, sheds noticeably more or thins in patches, speak to a GP rather than changing products.
Frequently asked questions
Does curl pattern decide which products I need?
Not by itself. Thickness, density, scalp condition and how worn the hair surface is tell you more than a type number.
Can porosity change?
Yes. Colouring, bleaching, heat and rough handling wear the surface, and new growth at the roots will usually behave differently from older lengths.
Is the float test reliable?
No. It mostly reflects surface tension and any oils or product on the strand, so it is a rough hint at best.
Why do my roots and ends behave differently?
Ends have had years of washing, styling and friction, while roots are new growth. Treating them differently is sensible.