Low porosity hair is not very absorbent. It is less able to take in water and hair treatments, so products may accumulate on the surface. Compared with high porosity hair, it is less prone to breakage.

The above information is from the New York Society of Cosmetic Chemists (NYSCC).

Low porosity hair allows less moisture to sink in, but it also allows less moisture to escape.

A person cannot increase the porosity of their hair without damaging it. However, people can care for their hair in a way that suits this hair type. The goal is to increase hydration and avoid any substances that keep moisture from entering hair shafts.

Keep reading to learn more about spotting and caring for low porosity hair.

A person brushing cropped low porosity hair.Share on Pinterest
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First, it is necessary to understand the structure of the hair. It has three layers:

  • The cuticle: This is the outermost layer of a strand of hair, and it consists of dead cells that overlap in a scale-like pattern. This layer protects the hair.
  • The cortex: This is the middle layer. It contains most of the hair’s fiber mass.
  • The medulla: This is the innermost layer of the hair.

The cuticle determines hair porosity. If the “scales” are very smooth and have few gaps, less water can penetrate to the deeper layers, and less water can escape. This means that the hair is less porous.

If there are gaps between the scales, more moisture can get through. A person may have typical or high porosity hair, depending on how much water can penetrate through the outer layer.

If a person knows how porous their hair is, it can help show why their hair behaves the way it does and how best to take care of it.

Here are the differences between low and high porosity hair:

Low porosity hair

Low porosity hair has a cuticle layer that lies very flat. This makes the hair more resistant to absorbing water and other substances. It also means that once moisture does penetrate the surface, the hair retains it for longer.

Hair may have low porosity if:

  • Any hair product accumulates on the surface.
  • The hair becomes stiff in response to protein treatments.
  • It takes longer to get completely wet in the bath or shower.
  • It takes longer to dry.

Straighter hair is more likely to have low porosity.

High porosity hair

High porosity hair has a cuticle layer that does not lie flat. The gaps between the dead cells allow moisture to penetrate and escape more easily.

Hair may be more porous if it is naturally wavy, curly, or coily. The twists in curly or textured hair cause the cuticle to lift up.

Also, porosity can increase due to mechanical or chemical damage. Mechanical damage can stem from any friction, such as from brushing, combing, or repeatedly wetting and drying the hair.

Chemical damage can result from harsh hair treatments and colorants, such as perms, relaxers, dyes, and bleach.

Hair may be highly porous if it:

  • becomes saturated with water quickly
  • dries quickly
  • absorbs products easily
  • breaks easily
  • often feels dry or frizzy

There are several ways to test hair porosity. An easy way to do this at home is called the float test.

To do this, place a clean strand of hair in a container of room-temperature water. If the strand floats before sinking, it is likely less porous. If it sinks immediately, it may be highly porous.

Other testing methods include:

  • Spray test: This involves spraying water on clean, dry hair and watching for results. Low porosity hair is slower to absorb the water and slower to dry. There may be visible beads of water on the hair.
  • Dynamic vapor sorption: This test measures the weight of hair as it becomes exposed to humidity. It is not one that people can typically do at home.
  • Fiber swelling: This measures the dimensions of a hair fiber after exposure to water. It would also be difficult to do this at home.
  • Gas adsorption and pore size analysis: This test exposes a hair sample to nitrogen. The results show the distribution of the nitrogen that the hair absorbs and the size of the pores in the cuticle.

Low porosity does not result from environmental factors, such as damage. Instead, it is something a person inherits, along with other characteristics of their hair.

Damage and aging may make low porosity hair more porous. Otherwise, this is generally not something that changes. However, it is possible to work with low porosity hair to keep it healthy and hydrated.

Looking after low porosity hair involves increasing the amount of moisture that gets into the hair shaft. It also involves avoiding any product that leaves residue. The NYSCC recommends:

  • Steam: Heat from steam relaxes the cuticle, opening up the dead cells somewhat. This allows water vapor to get into the hair shaft. A people can try using a handheld steaming device, a heat cap, or a shower cap to trap steam around the hair.
  • Humectants: These substances attract and trap moisture. Some examples of humectants include glycerin, hyaluronic acid, and honey. Look for shampoos, conditioners, or deep conditioning treatments that contain these.
  • Lightweight oils: Products that contain lightweight oils may help seal in moisture. A 2003 study found that out of mineral, sunflower, and coconut oil, the latter was best at penetrating the hair shaft. However, a more recent study found that using coconut oil led to no improvement in hair health. Also, bear in mind that oils repel water, so it may help to use a light oil sparingly, and only when also using steam or a humectant.

It may help to avoid:

  • Protein treatments: These may not absorb well into low porosity hair. The protein may also build up on the hair’s surface, making it stiff and reducing how much moisture can get in.
  • Silicones: In hair products, silicones such as dimethicone smooth the cuticle. But low porosity hair already has a smooth cuticle. Silicones may not be necessary and may form residue.
  • Butters: Substances such as shea and cocoa butter are very thick and repel water. In significant amounts, they may prevent moisture from absorbing into the hair and create a coating.
  • Using too much product: Because low porosity hair absorbs less of any type of product that other hair types, it may help to use less of it, even if the formula is suitable.

Low porosity hair absorbs moisture and hair products less effectively than more porous hair. Treatments may sit on the surface of the hair, rather than sinking in.

Lower porosity is more common in straight hair. Curly or coily hair is more likely to be highly porous. People can test the porosity of their hair at home by seeing how quickly a clean strand sinks in water.

It is not possible to make low porosity hair more absorbent in the long term. But using steam, humectants, and low-residue products can help keep the hair hydrated.