Why is hair porosity important? Does it really matter?
And how do you even find out if you have high porosity, medium porosity, low porosity or super low porosity hair?
The answers to these, plus (finally!) a legit, science-based porosity test that actually works.
First, what's hair porosity?
Unlike other hair typing systems, which are based on strand diameter (fine, medium, coarse), density (thin, medium, thick), or wave pattern (straight, wavy, curly), porosity is more evident in the way your hair behaves than how it looks.
That's because your hair's porosity isn't a feature you can see, at least with the naked eye. It's a measure of how your strands react to products, ingredients, and even air or water. The more willing your hair is to absorb these different things, or hold them on its surface, the higher your porosity.
Porosity also refers to the amount of pores or holes on the surface of your hair. Damaged hair tends to have lots of these, which makes it porous; prone to absorbing a lot of stuff due to its structure.
What are the porosity hair types?
The main porosity types are: high porosity hair, medium porosity hair, and low porosity hair . Low porosity hair can be divided into two further subtypes (moderately) low porosity hair, and super low porosity hair as when porosity gets very low it begins to act in almost the opposite way to other low porosity hair. Porosity occurs along a range, from extremely high to extremely low.
As a result, some high porosity hair is higher than others, and even within extremely low porosity hair (aka super low porosity) there are degrees of difference in how low your porosity is.
Why does hair porosity matter?
The main reason why hair porosity is important is because it controls how your hair interacts with pretty much everything, from the weather, to water, to the products you apply.
Your hair's porosity affects how it reacts to humidity. Image by Rodrigo Feksa.
Because it's based on how the surface of your hair behaves, porosity is a better predictor of how your hair will respond to any of these factors than traditional ideas used to classify hair, including strand diameter, curl type or ethnicity.
Knowing your hair's porosity will help you know how your hair is likely to react to humid weather, figure out what type of dye or other process you can use, and choose the right products and routines.
What's high porosity hair?
High porosity hair is the same as "porous hair"; it's hair with a more 'open' structure than other hair types. This can be for a variety of reasons. For one, the cuticle layers might be more raised, naturally, or due to severe chemical or physical damage.
The surface of the strand might have more pores or holes in it, due to damage. Or the outer layers of the hair might be completely or partially missing; this also happens due to damage.
Sometimes, it's all three. Either way, this makes the hair more porous: it will absorb more liquids, but usually release them very quickly, too. Ingredients that don't stick to the surface of other hair types can stick to the surface of high porosity hair and be very difficult to remove.
And frequently, products and ingredients that can't make it past the surface on other hair types get drawn in deep on high porosity hair and often seem to 'disappear'. Chemical processes also tend to happen faster on this type of hair, too. Check out the DHA High Porosity Guide to find out more about what makes hair high porosity, and how to take care of high porosity hair.
What's low porosity hair?
Low porosity hair is the type of hair we're all born with: it has flattened, compact cuticles, and a hydrophobic, 'water hating' surface that absorbs very little, very slowly.
Over time, most people's hair transforms to medium or even high porosity, due to wear and tear. The hair that doesn't change as much, and retains most of these characteristics is called low porosity hair.
Low porosity hair in general tends to have a resistant surface which is choosy about the products it will let sit on its surface let alone absorb. Chemical processes also typically take longer on low porosity hair because of this resistant surface.
Low porosity begins with moderately low porosity hair, which while slow, absorbs moisture and retains it very well, so tends not to suffer from dryness. It extends all the way to super low porosity hair at the very end of the porosity continuum.
What is super low porosity hair?
This is the second of the two subtypes of low porosity hair. While moderately low porosity hair, is what is often thought of as 'classic low porosity hair', super low porosity hair's extreme traits mean some people might not realise it is actually low porosity hair.
Super low porosity hair isn't just slow to absorb; it resists penetration by even water, almost completely. Most products slide off its surface or sit awkwardly on the cuticle, causing flaking or buildup instead of really connecting with the hair.
As a result, super low porosity hair doesn't have the great moisture retention typically attributed to low porosity hair because it can never take in enough to meet its needs in the first place.
On this type of low porosity hair, severe dryness is a common issue--despite the widely held idea that low porosity hair is doesn't suffer from moisture issues.
Medium porosity hair
As the name suggests, medium porosity hair stands somewhere in the middle. It's not resistant to processing or products, nor does it overly absorb or react to them. When this hair type is in good condition, its moisture needs are low and easily met by normal shampoooing and conditioning. However, when it is damaged, or exposed to extreme weather, both undermoisturisation and overmoisturisation can be a problem.
Medium porosity hair is often described as "normal porosity hair", although due to wide use of chemicals and low porosity hair being more common than originally thought, it is probably not the norm.
Hair porosity: How to know
You can determine your hair's porosity by its characteristics, which we've mentioned in this article, weighing them up and seeing which category your hair best fits into.
You can also take a hair porosity quiz like the one below, or physically do a hair porosity test, by applying water to your hair and observing what happens to the water, while it's on your strand.
If the water gets taken in very quickly, your hair is most likely high porosity. If that happens very slowly, or doesn't seem to happen at all, then you have low porosity hair. There's more on that below.
Hair porosity and drying time
The biggest clue to your hair's porosity is the drying time--but be careful. It does throw up more than a little confusion. . .
What hair porosity takes forever to dry?
Low porosity hair is notorious for taking long to dry. It can take several hours, sometimes well over a day, to airdry after washing. Why? The resistant surface on this hair type is hard to penetrate, but once water enters, it's even harder to leave.
Some low porosity hair can remain wet for several hours. Image by Ashley
This characteristic only applies to one type of low porosity hair, however: moderately low porosity hair. The lower the porosity goes, the more this effect weakens, until it disappears completely.
There are also some extreme cases, where high porosity hair is so porous, it begins to hold onto moisture for ages, just like low porosity hair. But in this case, it's not because the cuticle won't let the water leave; it's because the cuticle and lipid layers have been completely destroyed. The cortex underneath is very hydrophilic or water-loving, so will hold onto a lot of water, even though excess water absorption damages the hair.
Be warned: the 'porosity test' where you put a strand of your hair in a glass of water and see if it will float or not is bogus. It's been debunked many times over.
The main flaw is that it tends to give false results depending on how thick your strands are (heavier strands tend to sink regardless of porosity; finer ones tend to float), and what's on your hair (oil helps the hair float, other more humectant debris could make it more sinkable).
Floating a strand of your hair in a glass of water won't tell you your porosity. Image by Marco Flores.
If you want to use water to test your hair's porosity, there are much better ways.
For a rough test of your hair's porosity, you can just start with freshly shampooed, product-free hair. Then let it airdry. If it dries really slowly, you most likely have moderately low porosity hair. If it takes a few hours, that's likely to be medium, and if it dries super fast, you either have super low porosity hair or high porosity hair.
Step-by-step instructions on how to do a more accurate version of the porosity test are here.
Or try the no water porosity test:
Porosity test: no water version
If you want to know if you have low porosity or high porosity hair, but don't feel like applying water to your hair and then waiting with the patience of a scientist to see what it does, you can take the science-based porosity test at the top of this page, based on your hair's behaviour to give you a result in about 3 minutes.
When to test hair porosity
If you're going to do a physical test of your hair's porosity, you need to do it when your hair is clean, as in freshly shampooed; product-free - as in nothing applied after the shampoo, not even conditioner, or a drop of oil. Your hair should also be airdried - so don't use a blowdryer, as this can have a temporary effect on your hair's porosity.
For the most accurate results, follow the step-by-step instructions in the DHA High Porosity Guide which you can download for free here.
Hair porosity and products
Your hair's porosity has an overarching impact on how products work. Porosity decides which products can absorb into your hair, which ones get to adsorb (have some type of attraction or bond that sticks them to your hair's surface) or which ones will just sit there momentarily until they roll off, evaporate or get rubbed away.
And because different porosity types act differently in different weather, you'll need to change up your products (or at least how you apply them), based on the way your porosity interacts with the weather.
For example, humidity tends to be more of a problem for high or medium porosity hair than for low porosity hair types.
But if you have low porosity hair, whether moderately low or super low, the high levels of moisture in the air can be a good thing. Because of your hair's resistant structure, it's unlikely to absorb too much moisture. Instead, the warm, wet air could enhance the work of your leave in and actually calm frizz.
Moisturizing with La Aplanadora Leave In, topped by a humectant-rich jelly like Capilo Pro B-Natural Gel could help you make the most of sultry weather, especially if you tend to suffer from dryness in more temperate climes.
Which hair porosity is the best?
It all depends on which problems you'd prefer to have. Each level of porosity comes with its own advantages and tradeoffs.
High porosity hair tends to respond well to most products, but it tends to absorb them very quickly so you'll need to strategise on how to apply them. As a rule of thumb you'll need to use very concentrated treatments: think La Aplanadora or Silicon Mix, to get the conditioning effects to last a lot longer and keep on top of dryness.
You'll also need to be extra strict about chemical processes when you have this hair type, since high porosity hair tends to overprocess easily. In extreme cases, when the porosity is due to severe damage, it can become impossible for hair dye to take.
High porosity hair often cannot retain hair dye. Image by cottonbro
Most products are designed for medium porosity hair, which makes it easy to find products that work at this porosity level. However, medium porosity hair can be sensitive to humidity and get weighed down easily.
Moderately low porosity hair tends to be better at holding onto moisture than other hair types. The flipside is that great moisture retention tends to come with an extremely long drying time.
Low porosity hair in general tends to only 'like' a few products, so you might end up searching for longer before you find something that actually suits your hair. Few conditioners 'penetrate' because they can't bind well to the resistant surface typical of low porosity hair; one that does is Keratin Rich Detangling Conditioner.
Super low porosity hair rejects even more products and ingredients than moderately low porosity hair. It's also a lot harder to moisturise (though it gets easy when you know how).
The key is finding the products that match your hair's surface and then layering them: using a mild sulfate shampoo like Silicon Mix Hidratante, to clear the surface is the first step. Then, you need to infuse moisture and emollients: Baba de Caracol Conditioner overlaid with Baba de Caracol Mask, followed up with La Aplanadora Leave In and a low porosity sealant will help your hair overcome typical super low porosity moisture issues.
On the flipside, there are advantages. Super low porosity hair dries so fast after you wash it, you will probably never need a blowdryer if you have this hair type--Dominican Blowouts aside, of course. And because it's much more difficult to weigh down, super low porosity hair tends to have pretty good volume.
Can hair porosity change?
Yes. You can temporarily change the porosity of your hair by the products you use. Conditioners, for example are designed to lower the porosity of your hair; natural, healthy hair is always low in porosity.
You can also raise the porosity of your hair: shampoos do this temporarily, as in, they make your hair more hydrophilic or willing to absorb water. Interestingly, conditioners do too, initially, but by the time you've rinsed the conditioner from your hair, this effect switches and your hair becomes hydrophobic, more like low porosity hair, thanks to the complex layering of ingredients in conditioning formulas.
Those are the temporary changes. Permanent changes to your hair's porosity happen via damage. And they only tend to happen in one direction: increasing it.
Cuticle lifting, before and after. Image by Jae Hong Ji, Tae-Sik Park, Hae-Jin Lee, Yoon-Duk Kim, Long-Quan Pi, Xin-Hai Jin & Won-Soo Lee
The porosity increase happens after a structural change to your hair. One of the most common is cuticle lifting, where your cuticle scales either buckle or get decemented from your strand. Buckling can sometimes be remedied, but a fully lifted cuticle is a gone cuticle; it's permanently damaged.
Your hair's porosity can also rise when damage from heat, harsh styling or the environment leaves holes in your cuticle. The most common way to raise your porosity is by dissolving the hydrophobic outer layer of your hair, and creating holes in the next water resistant layer. Most chemicals used to alter colour or texture can do this and the effect is irreversible, a common side effect of bleaching, relaxing or perming hair.
That's why it's so important to protect your porosity as much as possible when it comes to the products, styling methods and any chemical processes you use on your hair. An excessive increase in porosity always comes with a rise in fragility, roughness and product issues. It can lead to severe breakage.
If you're looking to increase your hair's porosity on purpose, to get it to absorb more moisture, that strategy might work at first, but the damage that gets inflicted eventually becomes unsustainable.