No matter your hair type, one key factor that everyone—even straight- and wavy-haired people—need to know is porosity. If you don’t know your hair’s porosity, you might spend more time managing the trial and error of finding the perfect routine and products. Porosity determines how easily your hair can retain moisture. 

While wavy and curly hair tends to struggle more with moisture than straight hair, a person’s porosity level can make that mission even harder. Patricia G Williams, Creme of Nature brand educator, reminds us that “Knowing the porosity of your hair is as important as knowing your texture in selecting products for your hair care and styling regimen. Low or high porosity impacts what products work best on your texture.”

There are three porosity levels: high, medium, and low. High porosity hair struggles to retain moisture which slips out of the hair shaft through fully open cuticles. Medium porosity has less of an issue with moisture retention as the hair’s cuticles are regularly aligned. Note that medium porosity hair is often referred to as “normal” because it retains moisture well. 

Similar to high porosity hair, low porosity hair also fights moisture issues because the hair cuticles are tightly aligned. This means that moisture can’t penetrate the hair shaft easily. If you’re wondering how to determine porosity, all you have to do is try this quick one-minute test