Thursday, June 3, 2010
Chemistry of your hair: Fine hair
Our hair is made up of three layers - the medulla, the cortex, and the cuticle. The medulla is the important part when it comes to fine hair. The medulla is found only in the terminal hair on our bodies, and it is located in the middle of the hair shaft. It is composed of a protein called trichohyalin, and the degradation and metabolism of this protein contributes to the water holding properties of our hair.
Fine hair has a smaller diameter than average (fine hair is less than 60 µm, average 60 to 80µm, and thick more than 80 µm), so as you can expect, the ratios of the three hair layers will be different. In thick hair, the cuticle might make up 10% of the hair strand with 90% being the cortex; in fine hair, the cuticle might make up 40% of the hair strand with 60% being the cortex. Some fine hair is so fine it might not even have a medulla (but that has to be less than 40µm in diameter, and that's pretty much vellus or body hair). Even if you do have a medulla, it will be smaller than those found in other hair types. Which means you aren't getting the wonderful benefits of the proteins, which help to contain moisture in your hair! And because your cortex is smaller, your hair is not as strong as hair containing more cortex - like coarse hair!
Because fine hair contains more cuticle than other hair types, you have more cuticle scales that want to repel each other, creating more static and more fly-aways. You are also more prone to breakages, split ends, and damage through grooming, styling, and daily life. Sebum also spreads very quickly through fine hair, so woe betide the girl with fine, greasy hair! You want to shampoo daily because of the sebum, but you don't want the damage!
What is a girl to do?
You want to use daily use shampoo levels of surfactants even if you aren't washing every day. You want to use light conditioners that prevent static build up, which leads to fly-aways. Cationic polymers don't tend to be your friend - they can build up quickly on fine hair and weigh it down, so conditioning shampoos are probably not the best option. Cationic quaternary compounds can be your friend - cetrimonium chloride is awesome for fine hair, and light conditioners filled with proteins are a great choice. Don't not condition! They will cause the fibres in your hair to lay down in a parallel arrangement, which makes hair more manageable!