Hair absorbs water, a natural process important for its health and appearance. Hair strands are porous, possessing microscopic openings that allow water molecules to enter. Understanding this interaction between hair and water is central to effective hair care practices.
How Hair Absorbs Water
Hair strands consist of three main layers: the outermost cuticle, the middle cortex, and the innermost medulla. The cuticle, resembling overlapping roof tiles, serves as a protective barrier, influencing water penetration. While the cuticle’s surface can repel water, water molecules can still enter.
Once water bypasses the cuticle, it reaches the cortex, which makes up the bulk of the hair strand and is responsible for its strength and elasticity. Water molecules are attracted to the keratin proteins within the hair, forming temporary hydrogen bonds. This interaction causes the hair shaft to swell as it absorbs water, changing its shape and properties.
What Affects Absorption
The rate and amount of water absorption are governed by hair porosity, which describes the hair’s ability to absorb and retain moisture. Porosity is determined by the condition of the cuticle layer. Hair with tightly packed, flat cuticles has low porosity, making it difficult for water to enter, often causing water to bead on the surface.
High porosity hair has a cuticle layer with gaps and holes, allowing water to enter quickly but also to escape just as fast, leading to dryness. Normal or medium porosity hair has a moderately raised cuticle, enabling balanced absorption and retention of moisture. Hair damage from factors like heat styling, chemical treatments, and UV exposure can lift or create gaps in the cuticle, increasing porosity.
Caring for Water-Absorbing Hair
Understanding hair’s ability to absorb water is important for developing an effective care routine. “Pre-pooing” involves applying a treatment, such as oil or a mask, to dry or damp hair before shampooing. This protects strands from excessive water absorption and potential stripping by cleansers. Penetrating oils can be effective in minimizing waterlogging by being absorbed into the hair shaft. This pre-wash step helps maintain moisture balance and can make detangling easier.
Managing hygral fatigue, which is damage from repeated swelling and shrinking of the hair due to excessive moisture, is important. Hair with high porosity is susceptible to hygral fatigue because its open cuticles allow rapid water entry. To prevent this, balancing moisture with protein treatments can strengthen the hair. Sealing products like leave-in conditioners or heavier oils can help retain moisture without over-saturating the hair. Gently blotting hair dry with a soft cloth instead of vigorous towel drying can minimize friction and reduce damage.