The second axis
Hair porosity: the test, the chart, and what it means
Porosity is how well your hair absorbs and retains moisture. Two people with the same curl type can need completely different products because of different porosity. It matters more than curl type for most product decisions.
What is hair porosity?
Porosity refers to your hair's ability to absorb and hold moisture. It is determined by the structure of the cuticle - the overlapping scale-like layers that coat the outside of every hair strand. When cuticle layers lie flat and tight, water and products have difficulty penetrating (low porosity). When they are raised, lifted, or damaged, moisture gets in quickly - but also escapes quickly (high porosity).
Porosity can be partly genetic (your cuticle structure is partly determined by your genes) and partly acquired (heat damage, chemical processing, and rough handling all raise the cuticle and increase porosity over time).
Understanding your porosity level transforms product selection. A 4C with low porosity needs completely different products than a 4C with high porosity - even though their curl patterns are identical. Porosity is the missing piece most people find after spending years using products that don't work.
The float test: how to test your porosity
What you need
- A glass of room-temperature water
- A clean hair strand (one that fell out naturally - not pulled)
- Clean, product-free hair (wash and dry before testing)
- 3-4 minutes to observe
Wash your hair and let it fully dry with no products. Build-up from products can affect the result.
Collect a strand that fell out naturally when brushing or running your fingers through. Don't pull.
Place the strand on the surface of a glass of room-temperature water.
Wait 3-4 minutes without disturbing the glass.
Observe: does the strand float, sink to the middle, or sink to the bottom?
Floats on top
Low porosity
Sinks to middle
Medium porosity
Sinks quickly
High porosity
Low porosity
Float test: Strand floats on top of water after 3+ minutes
Cuticle structure: Tightly closed cuticle layers. Water beads on top and takes time to absorb.
Signs of low porosity
- -Water beads on your hair when you wet it in the shower
- -Products sit on top of your hair rather than absorbing
- -It takes a long time to get your hair thoroughly wet
- -Your hair dries slowly
- -Build-up accumulates quickly - you need to clarify often
Care approach
Low porosity hair resists moisture, so the goal is getting products IN. Heat helps: sit under a steamer or hooded dryer after applying leave-in to open the cuticle and allow absorption. Use lightweight, water-based products - heavy butters and oils will just sit on top and cause build-up. Clarify monthly to remove the build-up that accumulates from products that don't absorb fully.
What to use
Medium porosity
Float test: Strand sinks slowly, floating in the middle of the glass after 2-3 minutes
Cuticle structure: Slightly raised cuticle layers. Moisture absorbs and is retained at a balanced rate.
Signs of medium porosity
- -Hair gets wet quickly and dries at a normal pace
- -Products absorb without sitting on top, but don't disappear instantly
- -Hair holds styles well
- -Minimal or moderate frizz in normal conditions
- -Hair responds well to most standard routines
Care approach
Medium porosity hair is the easiest to maintain because the cuticle is balanced - open enough to absorb moisture, closed enough to retain it. A standard routine works: cleanse, condition, leave-in, light oil or cream seal. Avoid over-processing (heat, colour, chemical treatments) which can push medium porosity toward high porosity over time. A protein treatment once every 4-6 weeks helps maintain cuticle structure.
What to use
High porosity
Float test: Strand sinks quickly to the bottom of the glass within 1-2 minutes
Cuticle structure: Open or damaged cuticle layers. Absorbs moisture quickly but loses it just as fast.
Signs of high porosity
- -Hair gets wet almost instantly
- -Products absorb immediately but hair still feels dry quickly
- -Hair is very frizzy in humidity (moisture rushes in and out)
- -Hair dries very quickly
- -Tangles easily
- -May have been chemically processed or heat-damaged
Care approach
High porosity hair needs two things: protein to fill the gaps in the cuticle structure, and heavy sealants to hold moisture in once you've absorbed it. The LCO method (Liquid, Cream, Oil) often works better than LOC for high porosity - applying the oil last creates a heavier physical seal. Use anti-humectants in humid weather (castor oil, shea butter) rather than glycerin-heavy products, which will absorb ambient moisture and cause frizz. Protein treatments every 2-4 weeks fill the cuticle gaps and rebuild strength.
What to use
Type + porosity: the complete picture
The most accurate way to understand your hair is to know both your type and your porosity. Here are some common combinations and what they mean for your routine.
| Type | Porosity | Key challenge | Approach |
|---|---|---|---|
| 3A-3B | Low | Products sit on top; build-up fast | Lightweight products + heat to open cuticle; clarify often |
| 3A-3B | High | Moisture absorbs but leaves too fast; frizz | Heavy sealants + protein; anti-humectants in humidity |
| 3C-4A | Low | Moisture-resistant + tight coils | Steam + aloe-based products; never heavy butters first |
| 3C-4A | High | High moisture need + rapid loss | LOC/LCO + castor oil seal; deep condition every wash |
| 4B-4C | Low | Water-repellent + very tight coil | Steaming is essential; aloe, glycerin, lightweight oils only |
| 4B-4C | High | Maximum moisture need + fast evaporation | Shea butter + castor oil; protein every 2-4 weeks; protective styles |