Medium Porosity Hair: The Healthy Middle

Hair porosity is a measurement of damage state, not a hair type you were born with.

Medium porosity is the healthy middle: hair that takes in water at a normal, balanced rate and holds it without trouble. It is what most undamaged hair is, and it is the state you are trying to get back to if your hair has drifted into high porosity. The cuticle scales lie reasonably flat, the surface coating is intact, and the core bonds are sound. Medium porosity is less a category to manage than a sign your hair is in good shape.

How to recognise it

On the home tests, medium-porosity hair behaves moderately: a water drop sits on the surface for a little while and then slowly absorbs, neither beading forever nor vanishing instantly. A shed strand floats for a few minutes before slowly sinking. A wet strand stretches a little and springs back. In daily life: hair dries in a reasonable time, holds color for a normal span, takes product without either rejecting it or drinking it dry. The full method is in Hair Porosity Test.

Why "medium" is the goal, not a problem

Marketing tends to frame every porosity level as a condition needing its own product line. Medium porosity exposes how thin that framing is, because medium porosity is just healthy hair, and healthy hair does not need rescuing. The useful way to think about porosity is as a spectrum of damage: low at the intact end, high at the damaged end, and medium as the broad, healthy middle most hair occupies before bleach, heat, or years of wear push it toward high.

Keeping it there

The whole job with medium-porosity hair is preventing the slide to high porosity. That means protecting the surface coating (18-MEA) and the cuticle: limit bleach and high heat, rinse after chlorine, use gentle products, and clear hard-water mineral build-up periodically. If you color or heat-style, a bond-supporting treatment now and then maintains the core. You are maintaining a healthy structure, not repairing a broken one. The complete picture is in Hair Porosity: The Complete Science.

Frequently asked

What is medium porosity hair? The healthy, balanced state where water moves in and out of the strand at a normal rate. The cuticle is reasonably flat, the surface coating is intact, and the core bonds are sound. It is what most undamaged hair is.

How do I know if I have medium porosity hair? On the home tests it behaves moderately: a water drop sits briefly then slowly absorbs, a shed strand floats a few minutes then sinks, a wet strand stretches a little and springs back. In daily life, hair dries and holds color in a normal range.

Is medium porosity good or bad? Good. Medium porosity is essentially healthy hair. It is the state you want to maintain, and the state high-porosity repair aims to restore.

How do I keep medium porosity hair healthy? Protect it from the things that push hair toward high porosity: limit bleach and high heat, rinse after chlorine, use gentle products, and clear hard-water mineral build-up periodically. If you color or heat-style, an occasional bond treatment maintains the core.

Can medium porosity become high porosity? Yes. Bleach, repeated heat above about 180C, chlorine, color, and years of mechanical wear all push medium-porosity hair toward high porosity by stripping the surface coating, lifting the scales, and breaking the core bonds.

References

• Robbins, C.R. Chemical and Physical Behavior of Human Hair, 5th ed. Springer (2012).
• Breakspear, S. et al. Int J Cosmet Sci 47:639-651 (2025). doi