Porosity is the hairs ability or inability to absorb water. Although all hair is porous it is the level of porosity that varies. Hair with low porosity does not absorb moisture well and tends to resists chemical treatments. Black hair tens to be more porous than other hair types. Hair with high porosity absorbs water well when wet and looses moisture even more when it dries. A hair's pH and porosity as related: low pH products and styling treatments reduce hair's porosity causing tightening of the cuticle, high pH products increase the porosity by swelling the cuticle. High porosity is caused by heat-styling, sun, chemicals (relaxer/ color), and shampoos that strip. The more damage the greater the porosity...the more moisture it absorbs. It tends to be difficult to keep porous hair moisturized....a weekly ACV rinse, low pH shampoo, or neutralizing shampoo can help correct this problem.
How do you check for porosity? While hair is freshly cleaned and dried, grasp a clump of hair between you thumb and index finger and slide along from tips to root. If you feel bumps....your hair is slightly porous. Another way of testing is by plucking a clean strand of hair from your head and gently laying it in a glass of room temperature tap water. If it starts to sink right away it is very porous. The faster it sinks the higher the porosity.
Information attained from Davis-Sivasothy, Audrey. The Science of Black Hair. April 2011. e-book.
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