If you have low porosity hair, you know how frustrating it is to sit through the constant barrage of hair advice that doesn't work for your hair type.
Let's face it, low porosity hair is still a bit of an enigma to the natural hair community - even for those who have it.
So here are some little-known facts on low porosity you can use to finally master your hair.
1. Not all low porosity hair is the same...
We tend to talk about porosity in three big chunks: high porosity hair, medium porosity hair and low porosity hair. But there are quite a lot of porosity differences going on inside and on the edges of those categories.
Porosity isn't discrete: it varies across a spectrum. There are degrees of low porosity and the degree decides how your hair will behave. At the low end of the porosity scale, two broad types appear: moderately low porosity, which fits the textbook definition of low porosity hair, and super low porosity hair, the most extreme version.
2. How to tell the difference between super low and regular low porosity hair
Knowing how to do this will make a huge difference for people with the extremely low version. If it turns out you do have this hair type, you'll have to go all out to get moisture into it, so knowing what you're working with is very necessary.
There are two broad types of low porosity hair, moderately and super low porosity. Image by Taiisia Stupak.
Moderately low porosity hair takes long to get wet. You have to force (smooth or squeeze) the water in, soak it in a tub, or let it sit under a showerhead for ages. But it does get wet. Eventually.
Super low porosity hair doesn't. Most of the water doesn't get inside, no matter how much you smooth or squeeze, even if you stay under the shower till your fingertips start to prune. Another way to tell: If your hair has so many water droplets on it after you wash it, it looks like a crystal chandelier, you have super low porosity.
3. All hair starts out as low porosity
Even extremely high porosity hair. When all hair comes out of the scalp, it shows the same hydrophobic behaviour as low porosity hair because its cuticle is completely intact.
Wear and tear eventually makes hair more porous, and by the time a strand is a couple of inches out of the scalp it loses this low porosity status — except for the strands with the most compact, hermetically sealed cuticles, of course. Those will grow up to be your moderately and super low porosity hair.
All hair starts out with low porosity, even if it becomes high porosity later. Image by Luis Leon.
4. Not all low porosity hair takes forever to dry
One of the classic signs of low porosity hair is that it takes loooooong to dry. That could be hours, it could even be days. This hair type soaks up water slowly and it lets go of water slowly, too. But guess what? That defining characteristic is just true for moderately low porosity hair.
Super low porosity hair barely gets wet, so it doesn't take much to get it to dry. In fact, super low porosity hair is more likely to flash dry; it's not unheard of for this hair type to airdry within an hour — without heat. Why? Most of the water doesn't get inside; the porosity is that low.
After a quick dab with a cotton T-shirt or a microfiber towel, the surface water is gone. That leaves just the tiny amount that made it in to evaporate out.
5. Sulfate shampoo is better for low porosity hair than co-washes and low poos
Is this curly girl sacrilege? Nope. Most naturals have been told that sulfates are not the way to go, there's even a whole book on it. But that book wasn't written by someone with low porosity hair.
Medium and high porosity hair have little trouble absorbing moisture through tons of buildup, as commonly left behind by co-washes, conditioning low poos, and DIY clarifiers like baking soda.
Low porosity hair is naturally less absorbent. No way enough moisture is getting through all of that buildup.
Laureth sulfate shampoos can be a game changer in removing drying buildup from low porosity hair.
Another reason to use sulfates on low porosity hair: sulfates are really good at reducing the surface tension of water. That's the property that holds the surface of the water together, and makes water in a lake or in a glass look like it has a skin over the top.
The higher the surface tension, the harder it is for a liquid to wet or penetrate another surface, case in point your hair. Sulfates basically break that 'skin', lowering the surface tension of the water, making it easier for water molecules to enter your hair.
So in a way, sulfates literally help moisturise your hair. Just remember to rinse them out all the way when you're done and never use anything with "lauryl sulfate" on the label ("laureth sulfate" is cool).
6. Why one type of low porosity hair is harder to moisturise
Contrary to the most popular definitions, low porosity hair isn't always amazing at holding onto moisture.
If you're used to hearing about how good low porosity hair is at retaining moisture, you might be wondering why your low porosity hair is so dry.
Well, one of the two types of low porosity hair is usually going to have more trouble than the other in staying hydrated. There's a reason for this: once porosity drops past a certain point, hair is no longer absorbent enough to easily take in the moisture it needs.
So moderately low porosity hair can absorb some moisture and is naturally good at locking moisture in. Super low porosity hair can't absorb much moisture and is naturally good at locking moisture out. That's why the lowest porosity hair is also the driest hair.
If you have this hair type and you want it to be moisturised, you really need to get industrious. It means doing pretty much all of the things: Avoiding products that stop your hair taking in moisture; sectioning your hair and working everything in; using steam and conditioners like atrActiva Multivitamin, that can bind to low porosity hair's surface; learning how to insulate your hair; breaking out your Super Low Porosity Survival Kit. . . the whole nine.
8. What naturals call low porosity, hairdressers call resistant.
Ever been told by a hairdresser that your hair is 'resistant'? That's what many in the haircare industry call low porosity hair.
These hair types are the ones that are slow to take up colour, perms or relaxer, because their cuticle simply won't let them in. Porous or high porosity hair is the opposite: it not only sucks up moisture really fast, it processes really quickly, too.
Coarse hair is sometimes 'resistant' too: the extra cuticle layers mean some chemicals have to work a lot longer to change these strands. But not all coarse hair is resistant or low porosity. And not all resistant or low porosity hair is coarse, either.
9. Straight hair can be low porosity, too
Hair that is naturally straight is often low porosity too. Image by Jc Laurio.
While there's plenty of anecdotal evidence that 4b and 4c hair tend to have much lower porosity than looser curls, very straight to wavy hair (think 1a to 2b) is also often low porosity hair.
That's not all that surprising: Old-fashioned hairdressing guides often single out super straight East Asian and super curly African hair as 'resistant' to processing. It's stereotypical, as not everyone with these origins will have resistant hair, but it's not completely a myth.
Researchers have pinpointed the structural reasons behind the resistant hair common among people with very straight and very curly hair. These include having more compact cuticle layers, a factor that is often linked to low porosity.
10. 4c hair is almost exclusively super low porosity
4c hair isn't just about curl type. This hair type, formerly known as 'CNapps', is based on other characteristics too, including high shrinkage, sheen vs shine, and a dense appearance.
Most 4c hair is super low porosity hair. Image by Amanda Cardoso.
A natural lack of curl definition - the 'C' in CNapps stands for 'cloud' - is also one of 4c hair's most distinctive traits. The big reason behind this cloud: 4c's extremely low porosity.
Since water cannot easily penetrate or stick to the hair, it's harder for strands to arrange themselves into bundles when wet. Those bundles or clumps are how curl definition happens.
The curl pattern itself is not a factor in this; even straight hair tends to clump together when wet.
The clumping happens because of the absorbency of high porosity to moderately low porosity hair. It allows the water to get in, which leads to individual strands sticking to each other. If those strands happen to be curly, the result is clumpy, defined curls.
Since 4c hair has mostly super low porosity, its absorbency is much lower, so it's less likely to react to water in this way.
There is an exception to 4c super low porosity, though: finer 4c hair tends to be more porous than thicker hair, because it has fewer cuticle layers to form a barrier against water.
Bonus: Why Cold Water Rinses Fail On Low Porosity Hair
OK, so you probably already know this one: The final cold water rinse trick doesn't work on low porosity hair - but it's not because cold water closes your cuticles. That's a myth.
Cuticles only make dramatic movements when you physically break them off, or place them in extremely acidic or alkaline environments, like bleach, a relaxer, or a homemade baking soda clarifier.
Here are a couple, more likely reasons why cold water doesn't work well on low porosity hair:
One, the micelles that power your shampoo and conditioner usually don't perform as well in cold water. So you might experience slightly better lather from your shampoo in warmer water and definitely better emulsion from your conditioner.
The lower performance in cooler temperatures also makes it harder to rinse surfactants and the debris they remove from your hair, meaning a lot of conditioner, some shampoo and some moisture-blocking build-up will likely be on your strands after you're done rinsing.
Product that hasn't been washed or rinsed out properly will be obvious on low porosity hair which has a very low tolerance for build-up.
But the biggest reason is probably this one. The warmer water gets, the higher its energy and the lower its surface tension get. Hotter water is a better wetting agent, better equipped to penetrate your low porosity hair — and give it the moisture and plasticity it really needs.