Porosity is probably the most useful hair concept nobody talks about outside of curly hair circles. It explains why your best friend’s holy grail product does nothing for you. Why your hair takes forever to dry. Why color fades on you in two weeks but lasts six on someone else.
Once you understand your porosity, everything about your hair care routine starts making more sense.
What porosity actually means
Your hair has an outer layer called the cuticle — think of it like shingles on a roof. Porosity describes how open or closed those shingles are, which determines how easily moisture gets in and out of the hair shaft.
Low porosity: cuticles are tightly closed. Moisture has trouble getting in. Products sit on the surface. Hair takes forever to get wet and forever to dry. Color can be resistant because the cuticle doesn’t open easily.
Medium porosity: cuticles are moderately open. Moisture goes in and out at a balanced rate. This is the easiest hair to manage and the most responsive to products and color. If your hair generally cooperates, you probably have medium porosity.
High porosity: cuticles are very open or damaged. Moisture goes in quickly but also escapes quickly. Hair gets wet fast and dries fast. Color absorbs easily but fades fast. Hair is often frizzy because the open cuticle allows humidity to disrupt the shaft.
The float test (and why I don’t love it)
You’ve probably seen the advice to drop a clean hair in a glass of water and see if it floats (low porosity) or sinks (high porosity). It works in theory but it’s unreliable in practice. Product residue, surface tension, and whether the hair was truly clean all affect the result.
Better test: how does your hair behave with water? If it takes a long time to get fully wet in the shower and takes ages to air dry, you’re probably low porosity. If it absorbs water almost instantly and dries quickly, you’re probably high porosity.
Low porosity: what to do
Use lighter products. Heavy oils and butters will just sit on your hair and make it greasy. Liquid-based leave-ins and lightweight serums work better. Heat helps products penetrate — deep condition with a warm towel or shower cap. Clarify regularly because buildup is your enemy.
For color: your colorist may need to use a slightly higher developer or process a bit longer to get the cuticle to open. This is normal — don’t panic if your appointment runs a little longer.
High porosity: what to do
You need products that help seal the cuticle. Heavier creams, oils, and butters that low-porosity hair can’t handle are exactly what you need. Davines NOUNOU conditioner and mask are excellent for high-porosity hair — deeply hydrating with ingredients that help smooth the cuticle.
K18 is particularly important for high-porosity hair because a lot of high porosity comes from damage. If your cuticles are open because of chemical processing or heat damage, K18 repairs the keratin structure, which helps the cuticle lay flatter over time.
Always rinse with cool water. Cold water closes the cuticle and helps lock in whatever you just applied.
Porosity changes
You’re not stuck with one porosity forever. Chemical processing (color, bleach, relaxers) raises porosity. Heat damage raises porosity. Environmental exposure raises porosity. Virgin, unprocessed hair tends to be lower porosity.
This is why your hair care needs change over time — what worked before you started coloring might not work after. Your stylist should be adjusting recommendations as your hair changes.
Not sure about your porosity? Ask at your next Reverie appointment. We assess porosity and elasticity as part of every consultation.
