High Porosity vs Low Porosity Hair – How to Take the Test

Megan Dominion

This is a hot topic in the hair industry amongst stylists and hair technicians; so we’ve tried to break it down so that us every-day curlies and ‘good hair enthusiasts’ can navigate this topic with a bit more confidence! 

You need to understand your own hair first

You need to understand the structure of a single strand of hair to really get this. It’s just some quick biology, and then we’ll get back to the fun part of making your hair look amazing! In order to get the hair you want; you need to really understand what kind of hair you have so that you can give it what it needs. Your hair is basically a complicated houseplant. We need to make sure that you’re watering it enough, if that makes sense! And how much water your plant needs, and how often. Not all plants are the same, and it’s the same for hair types. 

Hair Structure diagram

Your hair has three layers. These are (from inside out) the Medulla, Cortex and the Cuticle. The Cuticle is the outer layer of your hair, and it’s job is to protect the Cortex. Your Cortex is where all the strength, moisture & nutrients of your hair is stored. What we need to find out is HOW STRONG your hair’s cuticle is. It’s kind of like the armour that protects your hair. They’re kind of shaped like roof tiles or pinecones. Some are further apart or closer together – and that’s how we establish how porous your hair is! We’re looking at how far apart the scales on your hair’s cuticle are.

Why does porosity matter?

Because once you understand your hair, you can finally give it exactly what it needs. And we need to ensure that those expensive or special products that you’re using are actually getting to the Cortex of your hair, and being absorbed by it! We want all those lovely water, oils and potions that you’re using to penetrate the cortex. If we know how strong the ‘armour’ or the cuticle is, then we’ll know exactly which soldiers to send! 

If the cuticles are closed, then it’s more difficult for hydration to penetrate your hair. On the other side; if the cuticles are too far apart or ‘open’ (more porous) then your hair will struggle to retain moisture and will have a dry, dull or frizzy appearance.

Hair Porosity Types diagram low, normal, high

The best porosity hair tests

There are three general tests that are used, but many have discredited the ‘floating hair in glass’ method, so we’d rather not mention it at this point. The two most common and widely used tests are actually so simple that you can do the first one right now, while you’re reading this! 

Woman with long brown hair doing the slide test

  • The Slide Test! 

Grab a single strand of your hair. Slide your fingers from the tip to the root in a smooth motion. Feeling any bumps or resistance along the way? This means that your cuticles are raised and you probably have quite porous hair or high porosity. Not feeling any bumps? You’ve probably got medium to low porosity. 

  • The Mist Test!

You might need a friend or partner to help you with this one. It’s also super easy! Make sure that you have good light. Take a spray bottle and mist your hair. What happens? If your hair is porous, the water will almost disappear and be absorbed straight away. If the water is just staying on your hair in the form of little beads, then that means your hair has LOW porosity. If the beads absorb after a minute or two, then you have medium porosity! 

If you’re still not sure, then you should pop in at your hairdresser and ask them to do a professional assessment for you. Knowing what kind of hair you have will help you to improve the health and appearance of your hair, and finally learn how to manage and take care of it!

What are the characteristics of different hair porosities?

Low Porosity: Hair products don’t absorb into your hair as they should, and it takes a long time for your hair to dry. 

Medium Porosity: TIt’s easy to style and it also takes really well to hair colouring and treatments. It’s also prone to be more shiny and healthy! And for our curlies – it also means it’s easier to get those perfect curls! However, hair CAN change from medium to high porosity from heat damage or hair chemicals, so please be careful with those perfect locks! 

High Porosity: This kind of hair allows moisture to soak into the hair easily, but it can struggle to retain any moisture or nutrients for too long. The cuticles are too far apart to keep any goodness inside for the Cortex. High porosity hair breaks easily, can be damaged and may also look dry or frizzy.

Girl with long brown hair

Can you change your hair’s porosity?

This is a yes AND no answer. Read our other articles including, ‘What is my Hair Type‘ and ‘Why your hair is taking forever to dry‘ for more info! 

Megan Dominion

Megan Dominion is SILKUP's Managing Editor. She's been down both the curly hair and skincare rabbit holes many times and loves that there's always something new to learn; a new science, method, product or personal experience.