Knowing your hair’s thickness and understanding the appropriate methods and products for that given thickness will help you achieve and maintain hair that looks and feels healthy. Thickness should be a factor you consider when deciding everything from your haircut to the styling products you buy. For example, those with thin hair, which can tend to be limp, might consider a haircut with layers. Layers help reduce the overall weight experienced by your hair, creating more volume.
While thin hair can easily be shaped, it can also be easily weighed down.
It has greater surface area compared to mass per hair strand than medium or thick hair. Therefore, oils, conditioners and products labeled creams or butters have more surface to coat per mass of hair. This is why oils and conditioners can weigh fine hair down more readily.
Thickness should also be considered before chemically treating hair.
Thicker hair is easier to permanently wave, due to its low cuticle-to-cortex (the part of hair that adds rigidity) ratio. For thick hair (usually somewhere around 100-mm in diameter) the cuticle only comprises ~15% of the fiber cross section. On the other hand, for thin hair (around 40-mm in diameter) the cuticle would comprise 36% of the total fiber cross section. The cuticle region of the hair is more resilient to this type of change. Fine hair is known to be resistant to waving, and this is likely due to its high cuticle content.
Thickness plays a prominent role in the physical behavior of hair.
Thicker hair tends to be stiffer and harder to style, whereas thin hair is more flexible and easily morphed. For example, people with thinner hair can sleep overnight with damp braided hair and are more likely to wake up to waves in their hair that last all day. This is less likely to work for those with thick hair, which needs the strong polymers found in gels or mousses to hold a certain style.
The need for added protein is determined by your hair’s thickness.
Proteins add structure and rigidity to hair. Since thin hair has a thinner cortex, it can greatly benefit from protein. Products typically contain protein in hydrolyzed form, and labels will advertise “strengthening” or “restoring” properties. Thick hair, on the other hand is already rigid, so adding unnecessary protein can cause hair to feel rough or coarse. If you do have thick hair, it’s best to experiment with protein slowly and carefully.