Hair Porosity: How to Recognise It and Adapt Your Routine
On The Wild Side
Key takeaway: porosity describes how the hair fibre exchanges water with its environment. It depends partly on cuticle condition and can vary across the same head of hair. The float test is too affected by surface tension, residue and strand diameter to serve as a stand-alone diagnosis.
What does porosity change in daily care?
A fibre with a more damaged cuticle may take up water quickly and lose it more easily. A less damaged fibre may take longer to become wet and allow products to build up on the surface. Colouring, heat, friction, ultraviolet exposure and the age of the lengths can all change this behaviour.
Why is the float test limited?
A strand may float because of surface tension or a product film, then sink when pushed under the water. One strand does not represent the whole head. Cosmetic science measures porosity under controlled conditions; a household glass does not reproduce them.
More useful observations
| Observation | Hypothesis to test | Cautious adjustment |
|---|---|---|
| Hair takes time to become wet and products sit on the surface | Build-up or low wettability | Reduce amounts and improve rinsing |
| Hair wets quickly then feels rough soon afterwards | More altered cuticle | Limit damage and condition consistently |
| Ends behave differently from roots | Progressive wear of the lengths | Treat zones separately |
| Behaviour changes after removing build-up | Product accumulation | Review frequency and amount |
Adapt the routine without overinterpreting
- Start with the smallest effective amount.
- Apply rich care only where it is needed.
- Observe detangling, drying time, suppleness and build-up.
- Change one variable over several washes.
- Reduce heat and friction if the fibre becomes brittle.
Porosity is not a scalp-health diagnosis and does not replace professional advice for shedding, pain or inflammation. Explore our hair care and, once launched, our selections for dry, curly or textured hair and fine hair.
Explore related guides and care
- Hair care
- Dry, curly and textured hair — activate at launch
- Fine hair and volume — activate at launch
- Silicone-free hair routine
Frequently asked questions
Does the float test really measure porosity?
It is too affected by surface tension, residue and strand diameter to be used on its own.
Does all the hair have the same porosity?
Not necessarily. Older ends and areas exposed to heat or treatments may behave differently.
Does porosity determine every product to use?
No. Diameter, shape, scalp condition, treatments and preferences also matter.
Sources and methodology
This guide separates general advice, published evidence and the limits of current knowledge. Sources were reviewed on 31 August 2026.
Content prepared by the On The Wild Side editorial team. Final editorial approval is required before publication.
