What determines hair texture? What's the structural differences between straight hair and curly hair? Truthfully science doesn't have all the answers to this subject yet. For example, why does hair texture change in some individuals as they get older? When I was younger, I think I had a looser curl pattern than the one I have now. A common guess to why hair texture changes is the changes in our hormones, but this is just an educated guess. There are several known factors that contribute to different hair textures: follicle shape, disulfide bonds, and sebum flow.
SHAPES
The shape of our hair cuticles are a result of the shape of our scalp's follicles. Hair that grows out of round follicles will have a rounded cuticle, thus straighter hair. Hair the grows out of crescent moon shaped follicles will take on a more oval shape, thus curlier hair. A good metaphor I read that paints a good picture is to think of it like the type of ribbon you use as a balloon tail. When you pass a scissor blade pass one side of the ribbon it curls up. This is the same concept as a hair strand passes through the half moon shaped follicle.
BONDS
As stated before in how do relaxers work, "Disulfide bonds are two sulfur atoms that are connected to each other. Straight hair, which has a rounded cuticle, has disulfide bonds that are aligned and scarce throughout the cuticle. Curlier hair has more oval, half moon shaped cuticles and more disulfide bonds that are arranged in a more slanting, zigzag pattern."
Hair is comprised of almost 90 percent keratin protein and 3 percent moisture. Hair is also made up of 4 different chemical bonds: peptide, disulfide, salt, and hydrogen. Getting into some chemistry, disulfide bonds are the second strongest chemical bonds in the hair, and are also called sulfur bonds. Polypeptide bonds form the keratin proteins found in hair, are the strongest bonds, and are also called keratin bonds. A disulfide bond is created when two sulfur atoms from two neighboring polypeptide bonds connect. Flatter, oval shaped cuticles are able to hold more cysteines, which is an amino acid containing sulfur, and allow them to come in contact with one another. And so with more sulfur atoms coming into contact, more disulfide bonds are able to be created, stabilizing the curly hair structure. A hair cuticle with a rounded structure, on the other hand, has less sulfur atoms and so allows less disulfide bonds.Unlike two of the other hair bonds mentioned, disulfides bonds are not broken by heat or water. Disulfide bonds, being one of the strongest bonds, is one of the reasons why our hair reverts back to out normal texture after straightening with heat or saturating our hair with water. It's what stabilizes our hair structure. Disulfide bonds can only be altered by chemical processes. It is why once we chemically treat our hair with relaxers and perms the change in texture is permanent.
Sodium hydroxide relaxers work by replacing the original disulfide bonds with a bond called a lanthionine bond, which only has one sulfur bond. Curly perms, on the other hand, work on the hair by forming new disulfide bonds with two sulfur atoms. Japanese straighteners (aka thio relaxers) use the same chemical as curly perms, but is able to straighten the hair. This is something I'm doing more research on.
AND FLOW
This is a topic where much more research still needs to be done. Our hair follicles contain sebaceous glands, which are glands that produce sebum (our natural oil) to lubricate our skin and hair and keep it supple. Our body's natural oil traveling from our scalp to the ends of our hair is commonly known as sebum flow. It's harder for sebum to flow through curlier hair, however, which makes sense because the oil has to slide around a spiral rather than a straight line. It makes me think of a kid trying to use a playground spiral slide, but you know how sometimes you found you had to slide yourself on those things? This is why curlier hair tends to be less oily than straighter hair. And then this is why curly hair tends to have a higher porosity than straight hair, because there is not as much oil to slick down the cuticle. The lack of sebum laying down the hair is why curly hair has more volume and frizz. The laying down of the hair strands also adds weight to the hair, which can result in a slightly looser hair texture.
There are healthy hair journey girls that take silica supplements for better hair growth and health notice that their hair texture becomes looser. There hasn't been much research for why, but an educated guess I have is that maybe there's an increase in sebum. Many of these girls that report a different hair texture also report that their hair feelings more nourished, which would be a result of sebum. I will also be trying out silica in the near future. Probably within a month.
There are healthy hair journey girls that take silica supplements for better hair growth and health notice that their hair texture becomes looser. There hasn't been much research for why, but an educated guess I have is that maybe there's an increase in sebum. Many of these girls that report a different hair texture also report that their hair feelings more nourished, which would be a result of sebum. I will also be trying out silica in the near future. Probably within a month.
