Understanding Hair Porosity: Key Information You Need to Know

Hair health is often defined by its texture, density, and diameter. Hair porosity—how well your hair absorbs and retains water or product—is another indicator. Knowing your hair's porosity level can provide insight into its health and why it behaves the way it does.

There are three types of hair porosity: low porosity, normal or medium porosity, and high porosity. Genetics and how you treat, style, and color your hair can influence your level or type of hair porosity.

Hair porosity is determined by how well your hair absorbs and retains water and hair products. The structure of your hair's cuticle (the outer layer of the hair shaft) influences porosity. Hair cuticles are comprised of overlapping scales that open and close to absorb and seal in moisture.

If the cuticles of your hair are very smooth and have few gaps, less water can penetrate the deeper layers, and less water can escape. This indicates that your hair is less porous. If there are gaps between the scales, more moisture can get through, making the hair more porous.

Knowing how porous your hair is can help you understand why your hair behaves the way it does and how to take care of it. Below are the different levels of hair porosity and how they affect hair's behavior.

With a normal porosity level, your hair absorbs and retains water at a normal rate. Research has shown that normal porosity hair absorbs 75% of the maximum water or product possible within four minutes. Normal or medium porosity hair will likely respond well to treatments such as bleaches, colorants, and relaxers and show predictable results. Drying and styling your hair may also be easier.

If your hair has low porosity, your cuticle layers are reinforced and lay flat, making your hair resistant to water and chemical treatments. You may notice it takes a long time to get your hair thoroughly wet and takes longer to dry. Products may build up easily on your hair's surface. Any chemical treatments you try may also be less effective.

Highly porous hair absorbs water easily and dries quickly. Your hair may feel dry, break easily, and look excessively frizzy. Chemical treatments may process faster than expected and cause damage. Coloring your hair may develop colors you were not expecting since it accepts hair colorants faster than less porous hair.

Many factors can influence hair porosity. Exposure to UV light, bleach, intense heat, or chemical relaxers can damage the hair strands and cause your hair to become more porous.

Certain hair types also have naturally porous hair. Textured hair or hair that is naturally wavy, curly, or coiled tends to have higher porosity than straight hair. This occurs because the cuticle lifts along the hair's fiber at various points, making it more porous.

How you treat and style your hair can also affect its porosity. Aggressively combing and brushing your hair on a daily basis can damage the cuticle and eventually make your hair more porous. Repeated wetting (causing swelling of the cuticles) and drying (causing de-swelling) can also damage your hair's cuticle over time.

If you are curious about your hair's porosity, there are a couple of ways to test it at home. These methods include the float test and the spray test.

The float test indicates hair porosity by showing how quickly a clean hair fiber sinks when placed in room-temperature water. To do this, take one of your hair strands from a hairbrush and place it in a glass of water.

Hair that quickly sinks to the bottom is likely high porosity. Hair that floats for an extended period is likely low porosity. Hair that sits on the water's surface briefly and slowly sinks may have medium or normal porosity.

The spray test displays how room-temperature water behaves when sprayed on your hair. To do this test, fill a spray bottle with room-temperature water and spray a section of your hair to see what happens. Hair that quickly absorbs the water is likely high porosity. If water beads on your hair and stays there for some time, your hair likely has low porosity.

Whether you have high- or low-porosity hair, caring for your hair based on its particular makeup can benefit your hair health. You may not be able to completely change your hair's porosity level—especially if it is due to genetics—but there are ways to repair damage and support your overall hair health.

Low-porosity hair does not absorb products or water well and has a higher tendency for product buildup. Here are some tips to consider for low-porosity hair:

High-porosity hair absorbs products and water easily, making it more likely for products to affect your hair's health negatively. Here are some hair care tips to try with high-porosity hair:

Hair porosity refers to how well your hair is able to absorb and maintain water and products. This characteristic is often used as an indicator of hair health and type. The porosity of your hair is determined by the structure of the cuticle, which is the outer layer of the hair shaft. Based on this structure, your hair may have high, low, or medium porosity.

Understanding the porosity of your hair can provide valuable information on how to properly take care of it and how it may react to color treatments and other chemicals. You can conduct a simple test to determine your hair's porosity by observing how it reacts when water is applied. Hair that quickly absorbs water tends to have higher porosity, whereas hair that is slow to absorb water has lower porosity.