Skip to Content

Hair Porosity Science: Tests, How to Know, Products, and More

Header image for an article on how to understand hair porosity types, including highly porous hair, low porosity hair, and normal porosity hair types

Hair porosity, in scientific terms, means creating pores within the structure of the hair. This definition of porosity also accounts for breaks and cracks as far as measuring whether the hair absorbs more water due to its porosity.

What Is Porosity?

Porosity is the hair’s ability, or the lack thereof, to absorb and to retain moisture or chemicals into the hair’s cuticle layers and cortex.

It is important to understand that porosity is a form of hair damage. As your hair ages, the hair’s cuticle layers begin to crack, peel and lift away. So, older hair usually has a higher porosity than newer hair.

The health of your cuticles is a good indicator of your porosity level. Healthy cuticles lay flat and retain moisture. Unhealthy cuticles do not lay flat and allow moisture to escape, easily causing frizz and excessive dryness.

For most people, the goal is to find that delicate balance between low and high porosity conditions, so your hair can thrive. Let’s explore why this is the case.

Beautiful African American female using a medium porosity hair care regimen
Image shows the structure of a healthy hair strand for a curly hair type
The structure of the hair is fairly complex as it includes a hyaline layer, cortex, medulla, and several other intricacies.

What is Low Porosity Hair?

Low porosity hair (flat tight cuticles) will not absorb moisture as easily as high porosity hair.

The cuticles are not damaged but the hair experiences dryness as if the cuticles were damaged.

The hair takes longer to saturate with water and conditioner may have little to no effect on the hair.

The cuticles are tightly sealed and it’s more difficult to penetrate them.

While it’s true that everyone’s hair is different, all hair naturally experiences porosity and permeability. There are many reasons why porosity occurs.

In this article, we’ll discuss some of the most common causes and our recommendations to combat typical porosity issues.

What is High Porosity Hair?

On the other end of the spectrum is high porosity hair. The cuticle layers have begun to crack, peel and lift away.

They are probably no longer attached to the strand of the hair, leaving the cortex unprotected. The damaged or missing cuticles are the cause of chronic dryness.

The cuticle is not intact and is unable to perform its job, which is to seal shut – retaining the moisture.

With high porosity hair, the hair absorbs moisture quickly but also loses moisture (or dries out) at an even faster rate.

Dealing with Hair Porosity Problems

The more porous your hair is the more moisture is usually absorbed. When your hair is highly porous it will often feel dry. However, it could very well absorb a great deal of water.

You might be thinking, “Great. Now my hair will absorb more moisture!”.

While it’s true that your hair will absorb more water when wet, unfortunately, it will also lose water at a faster rate as it dries.  Your hair cuticles cannot adequately retain moisture.

As your hair absorbs water, it expands to accommodate the water. If this process occurs too often, the hair can be damaged due to the amount of stress being placed on the hair. (source)

Common Reasons for Highly Porous Hair

Black woman with curly natural hair with raised cuticles wearing casual clothes

1. Periodic Usage of Shampoo, Towels, & Combs

Shampooing, towel drying, and combing your hair can damage the cuticle. These techniques are common since most people use them to some extent.

Although, high porosity hair is often caused when the hair is scrubbed vigorously with shampoo, rubbed with towels while drying, and when fine-tooth combs are used to remove tangles.

If you’re too aggressive while performing these common techniques, you’ll potentially cause lots of unnecessary hair damage leading to higher porosity levels, especially as your hair ages.

2. Older, Longer Hair is Generally More Porous

Your hair will incur more cuticle damage as it grows longer because it’s been shampooed, dried, and combed multiple times over the years. This hair damage is cumulative, so it increases with time. Read this article to learn more about the best moisturizers for low porosity hair.

Cute African American woman with a type 3 curl pattern wearing a green shirt and jeans

3. Ultraviolet (UV) Radiation Causes Cuticle Damage

Ultraviolet (UV) radiation can also damage your cuticles starting at approximately 200 hours of UV exposure.

Consider wearing a loosely fitting hat with you when you need to be outdoors for an extended period. Also, stay away from tanning lamps and beds.

4. Certain Chemical Treatments Encourage Porous Hair

Certain chemical treatments, like hair bleaching and creamy crack (i.e., hair relaxers) are causes of porosity. Cuticle layers can end up cracking, peeling, and lifting away when these techniques are used.

5. Other Factors

Outside of the above causes, porosity can also be caused by exposure to dirt, flat ironing, and blow drying with too much heat, cyclical thermal stresses, and humidity.

It’s important to note that everyone’s hair is different as well, meaning certain factors will cause more porosity in certain people than others.

Image showing how the hair behaves and its ability to absorb and retain moisture
This image represents a hair strand in its follicle, showing the epidermis, dermis, cortex of the hair, bulb, and sebaceous glands.

Frequently Asked Questions

Can Porosity Be Fixed?

When the hair’s cuticle becomes damaged, this cannot be fixed. While the cuticle does thin naturally when the hair becomes longer due to normal weathering, broken, chipped or missing cuticles cannot be replaced.

It is possible to temporarily patch the hair using hydrolyzed protein; however, you must remember that this is only a temporary solution and not a permanent fix.

Is It Possible To Open and Close the Hair Cuticles?

Note that this is not the manner in which a hair cuticle works. By suggesting that the cuticle opens and closes, you’re essentially implying that it operates as a door with a hinge and can be opened without any damage, then closed again. This is simply not what happens.

A hair cuticle can be raised to a slight degree; however, this requires highly sensitive instruments for detection as the distance to which it is raised may be as minute as one-millionth of a meter.

It is impossible to feel a raised cuticle by running fingers through the hair unless you have severely damaged cuticles.

A black lady with low porosity hair leans back as a few strands of hair fly in the wind

Is It Possible To Stop the Hair Cuticle From Being Raised?

The hair cuticle rises when the hair is wet, and people will need to wet their hair and handle it regularly. It is possible, however, to take steps to reduce the amount of damage done to the cuticle.

1. You can use coconut oil as a pre-wash to prevent the hair shaft from swelling. This pre-wash treatment may reduce the extent that the cuticle is raised.

2. You can use a conditioning shampoo that contains silicones. Silicones help minimize protein loss from the hair, caused by chipping and breaking cuticles.

Can Apple Cider Vinegar Help Close the Hair Cuticle?

In the past, we’ve recommended utilizing a periodic apple cider vinegar (ACV) rinse to treat porous hair by temporarily reducing the porosity level and making the cuticles smooth to increase water retention.

However, we haven’t been able to find a case study or scientific evidence that provides substantive proof that the low pH of ACV helps to close the hair cuticle.

It’s important to note that an ACV rinse may still help close the cuticle, although it’s not likely caused by the low pH based on research.

Products with higher pHs (9 and above), like hair relaxers, can raise the cuticle and potentially destroy it altogether. pH is a common abbreviation for potential hydrogen.

Can Cold Water Assist in Closing the Hair Cuticle?

There doesn’t appear to be scientific evidence that supports that cold water can help to close the hair cuticle.

It is seen, however, that heat is influential in raising the cuticle irrespective of the level of heat and the duration of exposure.

Of course, due to the lack of evidence for the impact of cold water on a cuticle, it is not possible to say that cold water does not influence the hair cuticle.

Can Protein Treatments Assist With Porosity?

Yes, they can. As is mentioned above, the hydrolyzed protein can be a temporary treatment for hair cuticles that are damaged as well as patching up areas where cuticles are missing.

This image shows a magnified (200x) human hair strand as we study hair damage mechanisms
This image shows a magnified (200x) human hair strand.

Determine Your Hair Porosity: Common Hair Porosity Tests

You’ve probably heard that you can test hair porosity at least two different ways, using the: (1) strand test, and (2) float test.

Before I explain the potential problems with these DIY hair porosity test methods, it’s important to understand how these tests are often conducted.

The Strand Test: Hold a strand of hair between your index finger and thumb. Using your opposite hand, slide your index finger and thumb along the hair strand.

If you feel irregularities that appear to be typical twists, turns, and angles of naturally curly hair, this is normal.

If you feel snags, your hair may be porous. If you don’t feel anything and it’s smooth sailing from tip to the root, your porosity is low.

This is a very unscientific process with an extremely low accuracy rate. We don’t recommend using the strand test as a reliable determination of your hair’s porosity level.

The Float Test: Harvest clean hair from your comb after you shampoo (allow hair to dry).

Place the dry hair in a bowl of room temperature water (since cold water will purportedly close the cuticles) to see if it will float or sink to the bottom. If it sinks, your porosity is high. If it floats, the porosity is low.

This float test, like the strand test, is unreliable and unscientific as a test for hair porosity. Hair strands will almost always float in water, due to the fact that the hair is typically covered in oil.

This oil is the naturally occurring sebum and any other hair products you may choose to include in your hair care routine.

Most people conducting this test report that the hair strands float for a period of time and only sink after some prodding.

Since oil will always float on water; therefore, the hair strand will continue floating. This does not necessarily mean the hair has a low level of porosity; it means the hair is light and has a full coating of oil that repels the water.

What if the Oil Is Removed Before Performing the Porosity Test?

If the hair’s oil is removed before the test is conducted, would this make the test valid or would it influence the porosity of the hair strand and the potential for the hair to sink?

If you choose to conduct the float test with a strand of hair that is freshly washed with shampoo, but not conditioned, then the test is potentially invalid if you typically use conditioner after shampooing.

In this instance, you would have altered the hair strand that you’re testing making the results of the test questionable.

Pretty African American woman with low porosity hair that uses minimal heat to maintain her curls

Does the Temperature of the Water Matter?

Some people claim that the temperature of the water will not influence the result of the porosity test; however, this probably isn’t true from a scientific perspective.

We were not able to find scientific evidence that supports that cold water can help to close the hair cuticle, but it’s unlikely that the water temperature has no impact.

For example, warm water can remove oil from the hair strand. Furthermore, hair is a protein and most proteins experience small structural changes as temperatures change.

Nonetheless, the most likely result of this test is that a single strand of hair will float.

Does Water Absorption Cause the Hair To Sink? What if Your Hair Floats?

When placing strands of hair in water, the hair strands will absorb water. As more water is absorbed, the hair strands will get heavier.

However, the hair strands may continue to float due to the oil coating.

If your hair sinks, it could be related to hair damage, but it could also be related to the natural density of hair.

This float test is unreliable, so don’t interrupt the results as facts.

Is There a Scientific Test for Hair Porosity?

There are scientific tests to determine hair porosity, but they’re usually complex and expensive. These aren’t the kind of tests that can be reliably conducted at home.

Related Articles


One final point of clarification, if your hair is damaged, they are no permanent solutions to repair damaged hair.

With damaged hair, you can only use these tips to patch up the weak spots and manage your problems temporarily.