Porosity refers to your hair’s ability to absorb and hold moisture. This is determined by the condition of the hair's cuticle layer (overlapping scales) and can be described as low, normal or high porosity.
Test your hair’s porosity
Start with clean, dry, product-free hair. Comb a section of hair, hold and spritz with a fine mist of water from 6-8 inches away. See how the water reacts – if it is absorbed immediately, then the hair is porous. If the water beads up or rolls off the hair, then it has low porosity.
Cuticles are compact and lie flat. Moisture isn’t easily absorbed and is more resistant to chemical processes. Using heat, a steamer or hooded dryer with deep treatments helps the cuticle layer to open up, so moisture is more readily absorbed into the hair shaft.
Cuticles are raised slightly and can absorb moisture more easily. However, unlike high porosity, hair will retain moisture.
Cuticles are highly-raised, so the hair absorbs and loses moisture quickly and easily, and can become dry and damaged easily. Chemically treated hair is often highly-porous due to damaged cuticles. Protein treatments help repair, strengthen and replenish hair by filling in the damaged holes on the hair shaft to reduce porosity. Layering products will help retain moisture for longer. Leave conditioner in, then apply a pure oil before using curl defining gel.