Hair porosity refers to the hair’s ability to absorb and retain moisture.
If you have low porosity hair, the cuticles of the hair shaft are tightly bound, making it harder for moisture to penetrate into your hair.

Determining if you have low porosity hair: A quick way to determine whether your hair is low porosity is to collect strands from a brush or comb and drop them into a glass of water. If your hair sits on the water and takes a noticeably long time to sink or never does, your hair is low porosity. Low porosity hair also takes a while to get wet (a while to absorb water into the hair), frequently feels dry because moisture doesn’t penetrate into the hair, and is protein sensitive.

Caring for low porosity hair:
◾As mentioned above, low porosity hair needs a little help in the moisture department. Deep conditioning with heat via a hooded dryer, steamer, conditioning cap, or even simply wrapping a hot towel around your hair when deep conditioning will help moisture from your conditioners penetrate into your hair.
◾Baggying/Greenhouse method. To use this method, simply apply the moisturizer of your choice and then cover your hair with a plastic cap.
◾Minimize use of protein products and focus on moisturizing products.
◾Do no overuse products with low pH levels (below 5.5/6) that further close your already tightly bound cuticles.