Wash your hair with a gentle shampoo and let it air-dry completely
Take a few clean, dry strands of hair
Fill a clear glass with room-temperature water
Place the hair strands into the water
Watch how quickly the hair sinks or floats
Hair that floats for a long time may be low porosity
Hair that sinks slowly may be normal porosity
Hair that sinks quickly may be high porosity
Spray water on a dry section of hair and observe how fast it absorbs
Check how long your hair takes to dry after washing
Feel how easily products absorb into your hair
Notice whether your hair resists moisture or loses it quickly