The porosity level is the hairs' ability to absorb and retain moisture
Low
Low porosity hair is generally healthy hair, but does not absorb or retain enough water. Its cuticle layer is tighter which makes it more difficult for this type of hair to absorb product. The use of heat with moisturizing products such as moisturizing and deep conditioners and oils can aide in moisture absorption for low porosity hair.
Medium
Medium or normal porosity hair indicates that your hair is healthy. Its cuticle layer is relatively loose and moisture can penetrate the hair for easier absorption. The more moisture that penetrates the hair, the healthier it is.
High
High porosity hair has a raised, overly porous cuticle layer and as such over-absorbs water and moisture. Because high porosity hair is very open it tends to be overly dry, frizzy and can break easily. When your hair is highly porous it can take in water, but not retain it because the cuticle layer is open so water that is absorbed is also easily released from the cuticle layer, leaving the hair unable to retain the moisture. Cuticle layer damage for high-porosity hair usually comes from coloring, heat damage or too much tension from ponytails or braids.
Porosity Test
Porosity Test 1
Take a strand of hair from your comb or brush and drop it into a clear glass of water. If the hair strand floats to the top, your hair is low porosity. If the strand slowly sinks toward the bottom, your hair is normal porosity. If the strand immediately sinks to the bottom, your hair is high porosity
Porosity Test 2
Run a few strands of hair between your thumb and index finger, starting at the ends and moving up the hair shaft toward the scalp. If the strands feel smooth, your hair is likely low to normal porosity. If the strands feel rough your hair is likely high porosity because the cuticle layer is loose and open causing the rough feeling of the exterior of the hair strand.
