Hair porosity is one of the most useful concepts in modern hair care and one of the most consistently misapplied. The basic idea is sound: the cuticle layer of each hair strand has a degree of openness that determines how easily water, oils, and active ingredients enter and exit the hair shaft. Three broad categories (low, medium, and high porosity) describe how that cuticle behaves. The right products and routine depend almost entirely on which category you fall into.
The misapplication comes from the float test, which the entire haircare internet has adopted as the standard porosity quiz despite the fact that it does not reliably measure porosity at all. A more reliable assessment takes five minutes and uses your normal wash routine as the test.
What porosity actually is
The outer layer of each hair strand is the cuticle, made up of overlapping flat cells like roof shingles. When the cuticle lies flat and tight, water and other molecules struggle to enter or exit. When the cuticle is raised or damaged, molecules pass through easily in both directions.
Three patterns describe most hair:
Low porosity hair has a tightly closed cuticle. Water beads on the surface during the first part of a wash, takes a while to fully saturate, and the hair takes a long time to dry. Conditioner often sits on the surface and feels coated rather than absorbed. Heavy oils build up easily.
Medium (normal) porosity hair has a moderately open cuticle. Water absorbs at a steady rate, conditioners absorb well, and styling products distribute evenly. The hair holds styles well and accepts most product types without issue. This is the easiest porosity to care for.
High porosity hair has a raised or damaged cuticle, often from chemical processing, heat damage, or genetics. Water absorbs almost instantly. Hair often feels rough or straw-like, especially at the ends. Conditioner absorbs quickly but the moisture also evaporates quickly. Color fades fast. The hair is prone to frizz in humidity and dryness in cold air.
A reliable five-minute porosity test
The float test is influenced by buildup, oils, and surface tension more than by porosity. A better assessment uses your normal wash.
Step one: rinse your hair under the shower for the first 30 seconds. Observe.
If water beads off the surface or runs off without your hair seeming to fully wet down, you likely have low porosity hair. Saturating the hair takes 60 to 90 seconds or longer.
If your hair wets evenly and quickly within 15 to 20 seconds, you likely have medium porosity.
If your hair absorbs water almost the moment it touches the strand, and the hair feels heavy and saturated within 5 seconds, you likely have high porosity.
Step two: apply conditioner and observe how it spreads and absorbs.
If the conditioner sits on top and you can feel a film on the surface, low porosity.
If it absorbs in within 30 to 60 seconds and the hair feels softer, medium porosity.
If the conditioner seems to disappear immediately and the hair still feels rough, high porosity.
Step three: after rinsing and gently towel drying, observe how fast your hair dries.
Hair that air-dries in over 3 hours from damp is typically low porosity.
Hair that air-dries in 1 to 2 hours is typically medium porosity.
Hair that air-dries in under 1 hour is typically high porosity.
If two of the three observations point to the same porosity, that is your category. If observations are mixed, you may have mixed porosity (common after bleach or color, where the roots are one porosity and the ends are another).
Routine for low porosity hair
The challenge with low porosity is getting moisture and product into the hair, not keeping it in.
Wash with a clarifying shampoo every 2 to 4 weeks to remove buildup. Daily-use sulfate-free shampoos work fine for routine washes.
Apply conditioner to damp hair under heat. Either run the shower hotter for 60 seconds after conditioner application, wrap a warm damp towel around the head for 10 minutes, or use a steamer if you have one. Heat opens the cuticle slightly and allows conditioner to penetrate.
Use lightweight, water-based products. Avoid heavy butters (shea, mango) and heavy oils (castor, olive) which sit on the surface. Lighter oils (argan, grapeseed, sweet almond) penetrate better.
Skip protein treatments unless you have specific damage. Low porosity hair does not need much protein, and frequent protein treatments can make it feel stiff.
Apply leave-in conditioners and styling products to wet hair, not damp hair. Wet hair has the most water for the product to bind to.
Routine for medium porosity hair
Medium porosity is the most tolerant category. Most standard product recommendations work.
Wash 1 to 3 times per week depending on hair texture and lifestyle. Sulfate-free shampoo on hair, sulfate shampoo on scalp if you use heavy products.
Standard conditioning routine. Most conditioners work. Deep condition once a week.
Light protein treatment once a month or as needed. Medium porosity hair benefits from periodic protein but does not require it constantly.
Most styling products work without modification. Curl creams, mousses, gels, oils all distribute evenly.
The maintenance is in not damaging the hair into high porosity. Heat tools below 350 degrees Fahrenheit, heat protectant always, minimal chemical processing.
Routine for high porosity hair
The challenge with high porosity is keeping moisture in and reinforcing the cuticle so it lies flatter.
Wash with sulfate-free, low-pH shampoo. High pH shampoos open the cuticle further. Look for shampoos in the pH 4.5 to 5.5 range.
Use the LOC or LCO method to layer moisture. L is liquid (water or leave-in conditioner), O is oil, C is cream. The layered approach traps moisture more effectively than any single product.
Protein treatments once a week. Hydrolyzed wheat protein, keratin, silk amino acids, and rice protein temporarily fill in the damaged cuticle. Olaplex No. 0 and No. 3, K18, and similar bond-rebuilding treatments work for very damaged hair.
Heavy butters and oils help seal moisture in. Shea butter, mango butter, castor oil, and olive oil all work as final sealing layers.
Apply leave-in conditioners to soaking wet hair (still in the shower or right after) so the product traps the maximum amount of water.
Cool rinses help close the cuticle temporarily. After conditioner, rinse with cool water for 15 seconds.
Avoid heat styling, or use a heat protectant designed for damaged hair (Olaplex No. 7, Briogeo Farewell Frizz Smoothing Shampoo line) and keep tools below 325 degrees Fahrenheit.
What changes porosity over time
Genetics set the baseline. Texture and curl pattern correlate but do not determine porosity. Straight fine hair can be high porosity from damage. Tight coils can be low porosity if undamaged.
Chemical processing raises porosity. Bleach is the most damaging, followed by relaxers, permanent color, demi-permanent color, and gloss treatments. Each chemical service opens the cuticle. Healthy hair recovers partially between services but cumulative damage shifts porosity upward over years.
Heat damage raises porosity. Repeated heat styling above 350 degrees Fahrenheit gradually breaks down the cuticle layer.
UV exposure raises porosity. Hair on the surface receives UV every daylight hour and slowly loses lipid content. UV-protective leave-in sprays are useful for people with high sun exposure.
Hard water raises apparent porosity by depositing calcium and magnesium ions that interfere with moisture absorption. A shower filter and periodic chelating shampoo (such as Malibu C or Ion Hard Water Shampoo) help.
Bond-rebuilding treatments (Olaplex, K18, GK Hair pH+) can partially reverse porosity damage by relinking broken bonds in the hair structure. Results are visible within 2 to 4 weeks of consistent use.
For more on routines for specific hair textures, see our methodology page and related hair care guides.
Frequently asked questions
Is the float test for hair porosity accurate?+
Not very. The float test (placing a strand in water and seeing if it sinks or floats) is influenced by product buildup, residual oils, and water surface tension more than by actual porosity. A better at-home test is observing how quickly your hair absorbs water during washing and how fast it dries afterward.
Can hair porosity change over time?+
Yes. Porosity is partly genetic but also significantly influenced by heat damage, chemical processing (bleach, color, relaxer), UV exposure, and hard water. Hair can shift from low to high porosity after a year of bleaching, and can partially recover with bond-rebuilding treatments and reduced chemical use.
What is the difference between low porosity and dry hair?+
Dryness is a state, porosity is a structural property. Low porosity hair has a tightly closed cuticle that resists water entry, so it can look dry but actually has trouble absorbing moisture rather than losing it. High porosity hair absorbs water easily but also loses it quickly, so it cycles between hydrated and dry states. The fix is different for each.
Do protein treatments help high porosity hair?+
Yes, more than for any other porosity type. High porosity hair has a damaged cuticle layer that protein treatments (hydrolyzed wheat protein, keratin, silk amino acids) can temporarily fill in. Once a week is typical. Low porosity hair generally does worse with frequent protein treatments because the closed cuticle does not allow water in to balance the protein, leading to stiffness.
Why does my hair feel coated when I use rich conditioners?+
Usually because you have low porosity hair and the conditioner ingredients are too heavy to penetrate the cuticle. They sit on the surface, building up over washes. Switch to lighter water-based conditioners and apply them with heat (warm towel or shower steam) to help them penetrate.
Jamie Rodriguez
Jamie Rodriguez writes for The Tested Hub.