Hair Porosity Explained: How to Test It and Why It Matters More Than Curl Type
Hair porosity determines how well your hair absorbs and retains moisture. Learn the science behind porosity, how to accurately test yours, and specific product recommendations for each level.
The bottom line: Hair porosity determines how well your hair absorbs and retains moisture—and it explains why one person’s holy grail product might be another’s disaster. Understanding your porosity level unlocks the key to selecting products that actually work.
Quick Picks: Products by Porosity
Match Your Porosity
Find products designed for how your hair absorbs moisture:
have low porosity hair (products sit on top)
have high porosity hair (moisture escapes quickly)
need deep moisture for high porosity hair
Not sure about your hair type? Take our quick quiz to find out.
The Science Behind Porosity Lies in Cuticle Structure
Each hair strand consists of three layers: the medulla (soft inner core, present only in thicker hair), the cortex (middle layer containing keratin proteins and pigment), and the cuticle—the outermost protective layer that determines porosity.
The cuticle comprises 8-10 overlapping translucent cells arranged like tiles on a roof or shingles. These cells are bound together by lipids and coated with an oily substance called 18-MEA (18-methyleicosanoic acid), which naturally repels water.
Low porosity means cuticle cells lay flat and tightly packed with minimal gaps—moisture struggles to penetrate but, once inside, retention is excellent.
Medium porosity features cuticle cells that are slightly raised but not damaged, allowing balanced moisture exchange.
High porosity indicates significantly raised or damaged cuticles with gaps and holes that allow rapid moisture absorption but equally rapid loss.
Testing Methods Ranked by Reliability
The Float Test (Least Reliable)
This popular test involves dropping a clean hair strand into room-temperature water: if it floats, supposedly low porosity; sinks to the middle, medium porosity; sinks quickly, high porosity.
Problems include: surface tension affects results regardless of porosity, any product residue or natural sebum causes floating, hair density/thickness influences sinking speed, and the test only examines individual strands rather than whole-head behaviour.
The Strand Feel Test (Moderately Reliable)
Take a clean, dry strand and slide fingers up the shaft from ends toward scalp (against the grain). Smooth feeling suggests low porosity (tight, flat cuticles); slight bumps but easy glide indicates medium; rough, bumpy texture suggests high porosity (raised cuticles). However, this remains subjective and depends heavily on technique.
Water Absorption Test (Most Reliable Home Method)
On clean, product-free hair, spray a section with water. Observe: if water beads up and rolls off before slowly absorbing, that’s low porosity; if water absorbs at moderate pace, that’s medium; if water soaks in immediately and disappears quickly, that’s high porosity. This test reflects real-world product behaviour.
Observation Method (Most Practical)
The most reliable approach involves observing your hair’s behaviour over time:
- How long does it take to get fully wet in the shower?
- How quickly does product-free hair air-dry?
- Do products absorb or sit on the surface?
- Does your hair respond well to protein, or become stiff and straw-like?
Low Porosity Hair Needs Lightweight Products and Heat
Low porosity hair is identifiable by: taking a long time to get wet in the shower, water beading on the surface, products sitting on hair rather than absorbing, very long drying times, hair maintaining curl definition even when wet, and natural shine from smooth cuticles.
The challenge: Getting moisture IN. The tightly packed cuticles resist penetration, but once moisture enters, it’s retained well.
Product Requirements
- Lightweight, water-based products (water as first ingredient)
- Humectants: glycerin, honey, aloe vera—attract moisture from the environment
- Light oils: argan, jojoba, grapeseed (penetrate better than heavy options)
- Protein-free or low-protein formulas (low porosity hair often has an intact protein structure)
- Hair milks rather than heavy creams
Specific Products for Low Porosity
- Curlsmith Hydro Style Flexi Jelly (mid-range)—water-based, lightweight gel
- Giovanni Direct Leave-In (mid-range)—protein-free, very light
- Umberto Giannini Curl Jelly (budget-friendly)—medium hold without heaviness
- Innersense I Create Lift Foam (mid-range)—light protein, volumising
- Bouclème Curl Defining Gel (mid-range)—lightweight hold
Clarifying is essential. Low porosity hair is extremely prone to buildup, so clarify every 1-2 weeks. Bounce Curl Gentle Clarifying Shampoo works well.
High Porosity Hair Requires Protein, Sealing, and the LOC Method
High porosity hair gets wet instantly, absorbs products immediately, dries very quickly, feels constantly dry despite moisturising, tangles easily, and appears dull (rough cuticles don’t reflect light). Hair may feel “mushy” when wet in severe cases.
The challenge: Moisture enters easily but escapes just as quickly through gaps in the cuticle layer.
Product Requirements
- Heavier, richer products: thick creams, butters (shea, mango, cocoa)
- Sealing oils: Jamaican black castor oil, olive oil, avocado oil
- Protein treatments: keratin, hydrolyzed proteins—fill gaps and strengthen structure
- Anti-humectants in humid weather to prevent excessive moisture absorption
Specific Products for High Porosity
- Curlsmith Double Cream Deep Quencher (mid-range)—heavy, protein-free deep conditioner
- Shea Moisture Manuka Honey Masque (mid-range)—contains protein, very rich
- Aphogee Two-Step Protein Treatment (mid-range)—heavy protein repair
- Bouclème Protein Booster (mid-range)—add to conditioner for customisable protein
- Curlsmith Bond Curl Rehab Salve (premium)—medium protein treatment
- Jamaican Black Castor Oil (various brands, budget-friendly)—sealing
The LOC Method
LOC Method for High Porosity Hair
L - Liquid
Apply water or a water-based leave-in to hydrate hair.
O - Oil
Apply oil immediately to seal moisture BEFORE it escapes.
C - Cream
Apply styling cream or gel for additional moisture and styling.
Open in Routine Builder to customize, save, or share this routine
The oil layer seals open cuticles and prevents rapid moisture loss. Using cream before oil (LCO) can risk hygral fatigue—damage from repeated swelling and contracting of the hair shaft.
Medium Porosity Represents the Balance Point
Medium porosity hair wets fairly easily (not instantly), absorbs products at reasonable pace, air-dries in moderate time, holds styles and colour well, and generally appears healthy with good elasticity.
This “Goldilocks” state allows flexibility with products and techniques. Both LOC and LCO methods work, and there’s tolerance for variety in product weights. The goal is maintaining this healthy state through gentle care and preventing damage that would shift porosity higher.
Compare Products by Porosity
Products for Different Porosity Levels
| Product | Weight | Hold | Protein-Free PF | Fragrance-Free FF | Price | Best For |
|---|---|---|---|---|---|---|
| Curlsmith Hydro Style Flexi Jelly Curlsmith | Light | | – | – | ££ | Low porosity—lightweight, water-based |
| Giovanni Direct Leave-In Giovanni | Featherlight | | ✓ | – | ££ | Low porosity—protein-free, ultra-light |
| Bouclème Protein Booster Bouclème | Light | | – | – | ££ | High porosity—customisable protein |
| Curlsmith Bond Curl Rehab Salve Curlsmith | Medium | | – | – | £££ | High porosity—intensive protein repair |
| Curlsmith Double Cream Deep Quencher Curlsmith | Heavy | | ✓ | – | ££ | High porosity—deep moisture |
Can Porosity Change Over Time?
Natural porosity is genetic and permanent. However, damage can increase porosity by destroying the cuticle layer:
- Bleaching and lightening dramatically raise porosity by creating gaps
- Chemical relaxers, perms, and frequent colouring open cuticles
- Heat styling damages cuticle structure over time
- Harsh brushing and friction cause mechanical damage
You cannot permanently reverse cuticle damage—hair is dead tissue. However, you can temporarily improve appearance using protein treatments (which patch gaps), bond repair products, acidic rinses (which help cuticles lie flatter), and protective care while healthy hair grows out.
Common Porosity Misconceptions Debunked
“High porosity hair always needs protein”—While protein often helps high porosity hair, some may need more moisture than protein. Balance is essential; excessive protein causes brittleness.
“Low porosity hair doesn’t need moisture”—It absolutely does; the challenge is getting moisture in, not whether it’s needed.
“The float test is definitive”—It’s widely debunked by scientists and trichologists as unreliable.
“Porosity is consistent across your head”—It varies by section and along individual strands. Roots (new growth) are typically lower porosity than ends, which have experienced more wear.
Find Products for Your Porosity
Browse Lightweight Products
For low porosity hair that needs products that won't sit
Browse Rich, Moisturising Products
For high porosity hair that needs sealing and hydration
Browse Protein Treatments
For high porosity hair that needs cuticle repair
Next Steps
- Take our Hair Quiz to identify your porosity, curl type, and get personalised recommendations
- Check your products with our Ingredient Checker—see if they suit your porosity
- Experiment with the observation method over 2-4 weeks to understand how your hair behaves