I am back designing education this time for the Moroccanoil brand and revisited the subject of the hair’s layers. It is one of the first hair theories we learn as a Professional, but its only through experience that we realise its importance as it helps to explain why things happen. Even recently during a coaching session with a very experienced colourist, I was able to direct him back to his understanding of the hair’s layers being the root of his particular hair colouring challenge. In this blog I start to peel away the hair’s layers and leave you with something to ponder.
Our hair is an amazing fibre and it covers virtually our entire bodies. It’s #1 priority is to protect us from UV damage and to help with thermal regulation, after all we didn’t always wear clothing or have SPF. We have two different types of hair on our bodies; Vellus hair the fine, downy, barely visible hair the covers most of our bodies. And Terminal hair the thicker, longer coloured hair we find covering our scalps and other areas on which we spend a lot of money on plucking, waxing, shaving, shaping, bleaching and even lasering. If you would like to know more about hair growth click here.
Our hair is made up of three layers:
The cuticle; the outer hard layer that is made up of many layers and it is there to protect the softer inner layer of our hair.
The cortex; the largest of the hair’s layers that makes up the bulk of our hair.
The medulla; which is only present in thicker hair.
The Cuticle Layer: is made up of many layers, anywhere between 4-10 layers and yes there are exceptions some individuals can have hair with even more cuticle layers. The individual flat cuticle cells are very hard and overlap each other to give a very strong protect layer that resembles the scales of a fish. The cuticle layer does not have any colour so when you see the hair’s colour you are looking through to the melanin inside the cortex. The cuticle accounts for about 13% of the entire hair strand, it has a very important role to play in protecting the softer inner hair and is so hard it can leave groves on combs and brushes.
When we wash our hair, it is our cuticle layer that can make wetting the hair difficult as the outer side of each cuticle cell is hydrophobic but eventually it will allow water and liquids to pass through as the underside of each cuticle cell is hydrophilic.
The cuticle layer does not open and close like a door to the inside, but rather a change in pH will swell the entire hair which helps to expand the pathways though the cuticle layers. Think about trying to work your way through a dense crowd, now think of the same crowd in a bigger space the individuals can space out a little more and it is easier for you to work your way through. The same thing is happening the cuticle layers, when the hair is at its normal pH it is so tightly compact it makes it very difficult for anything to pass through it. Introduce a higher pH than the hair’s 5-6 and a space is created making it easier to get through this protective layer; yes, the higher the pH the greater the space and easier it is to get ‘stuff’ into the hair. If you would like to discover more about pH check out my blog here.
The products that we use that work directly on the cuticle layer are; direct-acting dyes that sit on and within these layers meaning every time we wash our hair they can be easily removed. Care products such as shampoos, conditioners and treatments. Having a healthy cuticle layer will encourage shine and protect the inner hair. Styling products will sit on top of and within the first few cuticle layers of the hair.
Complications;
Damage to the cuticle layer will mean the hair is more prone to further damage and in the extreme start to fall apart as can be seen with split ends or even breakage along the midshaft.
Staining of the cuticle layer; this can happen when direct-acting dyes or even colourants within a product (I had it happen to my hair with a green coloured conditioner) stain the cuticle layer. Like any annoying stain, it can be very difficult to remove. Even bleach will quite literally pass through the cuticle into the cortex and miss the offending stain. It will need a lot of washing to eventually get it out of the cuticle.
The Cortex; is the bulk of the hair. It is made up of long telescopic cells that bundle together like ropes which give it a very strong structure. A lot is going on in this layer, it is where the ever changing moisture for our hair is held and although the cortex itself has no colour it contains the small granules of melanin that give us all our unique hair colour. More information in melanin here.
When we want to make big changes to the hair we are working within this layer. Oxidising colours, permanent waves, straighteners and relaxers all have a high pH that allowing pathways through the cuticle layer into the cortex where these products are designed to target. The pH does more than just open the pathways it creates the right environment within the cortex to allow the changes. Although the cortex is not as hard as the cuticle it is still very strong.
It is often taught that the cortex contains the hair’s structural bonds and it does but so does the entire hair. Bonds temporary or permanent are holding the entire strand of hair together and allowing it to be shaped and reshaped. I like to think of the bonds as a spiderweb that has been spun throughout, within and on the outside of our hair.
Complications;
Damage within the cortex will happen through oxidation, not only from oxidative products we purposely apply but also from UV. We know it can make the hair more porous, literally creating holes in the cuticle layers and within the cuticle fringes; the space where the cuticle and cortex meet. It can bleach the natural melanin or artificial colour and cause the cortex to lose moisture very quickly leaving the hair brittle.
The Medulla; is only found in thicker hair. It is thought to be responsible for thermal regulation. The medulla itself is made up of a honeycomb structure which also appears to help with light reflection consequently the improvement of shine. There is relatively little research from a product manufacturing perspective as none of the products we use work on the medulla and the medulla does not affect any of the product we apply.
Complications;
Not so much a complication than an observation and hypothesis, we are still learning about the hair. When our hair turns grey hair that has a medulla experiences and interesting change beyond the lack of melanin; the medulla increases in size. I’ve never been able to find an explanation for this. That means the hair remains the same size in diameter, the medulla increases, the cortex shrinks and the cuticle remains the same. Now to my hypotheses, some thicker hair types appear to accept an oxidative colour into the hair very well but when washed and dried the result can look translucent. Has this to do with a lack of capacity in the shrunken cortex?
Some food for thought, stay curious and stay safe
Caroline
