What Porosity Measures

Hair porosity describes how readily your hair cuticle allows moisture and products to enter the hair shaft and how well it retains what enters.

The hair cuticle is the outermost layer of each hair strand, composed of overlapping keratin scales arranged like fish scales or roof tiles. When these scales lie flat and close together, the hair has low porosity. When they are lifted or damaged, the hair has high porosity.

Low porosity: Tightly overlapping scales resist entry. Water beads on the hair surface rather than absorbing quickly. Products sit on top rather than entering the shaft. This is not poor hair health; many people with low porosity have strong, healthy hair that simply requires specific product strategies.

Medium (normal) porosity: Scales allow moisture to enter at a balanced rate and retain it reasonably well. The most adaptable hair type for products.

High porosity: Raised, damaged or widely spaced scales. Absorbs moisture and products quickly. Loses them just as quickly. Hair feels dry shortly after conditioning. Produces the most frizz in humidity (atmospheric moisture enters the shaft rapidly and unevenly).

How to Test Your Hair Porosity

The Float Test

Take 2 to 3 clean, dry strands from your comb (not from a brush). Drop them into a glass of room-temperature water. Wait 4 minutes without disturbing the glass.

  • Hair floats: Low porosity
  • Hair sinks slowly (resting at the midpoint): Medium porosity
  • Hair sinks immediately: High porosity

Limitations of the float test: Strands coated in product residue, silicones or oils produce inaccurate results because the coating affects the water absorption rate rather than the cuticle structure. Test on hair that has been clarified (washed with a clarifying shampoo) within the past 48 hours.

The Slip Test

Run two fingers up a single hair strand from tip to root.

  • Smooth, no resistance: Low porosity (scales are flat and smooth)
  • Slight roughness: Medium porosity
  • Significant roughness, snags or bumps: High porosity (raised scales catching your fingers)

The Spray Test

Spray a small section of dry hair with water from a fine mist bottle. Observe immediately.

  • Water beads and rolls off: Low porosity
  • Water absorbs within 10 to 15 seconds: Medium porosity
  • Water absorbs immediately, hair darkens with moisture within 2 to 3 seconds: High porosity

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Products for Low Porosity Hair

Low porosity hair's main challenge is product absorption. Products designed for this type work with the closed cuticle rather than against it.

What works:

  • Heat activation: Applying a deep conditioner under a heated cap or in a steam environment opens the cuticle enough for the conditioner to penetrate. Without heat, deep conditioners sit on top of low-porosity hair without entering.
  • Light, water-based products: Humectant-rich (glycerin, hyaluronic acid) leave-in conditioners in a thin, water-based formula penetrate more readily than thick creams or oils.
  • Protein-free conditioning: Low-porosity hair is often protein-sensitive; protein molecules are too large to enter a tightly closed cuticle and instead coat the hair, causing stiffness. Use protein-free conditioners for daily maintenance.
  • Lightweight oils: Jojoba, argan and grapeseed oils have smaller molecular sizes than heavier oils (castor, olive) and penetrate closed cuticles more effectively.

What causes build-up on low-porosity hair:

  • Heavy butters (shea, cocoa, mango): Sit on the cuticle rather than penetrating; accumulate with repeated use
  • High-protein products: Coat the cuticle and cause stiffness
  • Silicone-heavy products: Without sulphate shampooing, silicones accumulate and weigh down low-porosity hair

Clarifying frequency: Low porosity hair builds up product more readily than high porosity hair. Use a clarifying shampoo once every 2 to 4 weeks to reset the surface.

Products for High Porosity Hair

High porosity hair's challenge is moisture retention. The raised cuticle allows rapid moisture entry and equally rapid moisture loss. Products for this type focus on sealing.

What works:

  • Protein treatments: Hydrolysed keratin and hydrolysed wheat protein temporarily fill the gaps in the raised cuticle, slowing moisture loss. Use once every 2 to 4 weeks. Overuse causes stiffness and brittleness.
  • Heavy oils: Castor oil, olive oil and avocado oil have larger molecular structures that sit in the cuticle gaps and reduce moisture escape. Apply to damp or wet hair as the final sealing step.
  • The LOC method: Liquid (water-based leave-in), Oil (a sealing oil), Cream (a thick butter or cream) applied in sequence seals each layer before the next. This sequence provides the most sustained moisture retention for high porosity hair.
  • pH-balancing rinses: Apple cider vinegar diluted in water (1 tablespoon ACV to 1 cup water) applied as a final rinse temporarily flattens the raised cuticle and improves shine and frizz control.
  • Anti-humidity products: High porosity hair absorbs atmospheric moisture readily; anti-humidity gels and serums (applied over the LOC method) create a sealing layer that slows humidity absorption.

Cold water rinse: Rinsing conditioner with cool or cold water (rather than warm) temporarily closes the cuticle and improves the effectiveness of each conditioning session for high porosity hair.