Synthetic hair
Synthetic hair is made of a wide array of different synthetic fibers. Synthetic hair, just like human hair, comes in weave (weft) and single strands (bulk) for braids. Synthetic hair does not last as long as human hair because it gets quickly damaged by friction and heat. The quality of hair varies greatly. Depending on quality, it may never look like human hair, as it can be stiff and move differently than human hair. Synthetic hair is much less expensive than human hair. Heating appliances such as curling irons and straightening combs generally should never be used on most types of synthetic hair. There are some newer versions of synthetic hair that are more resistant, human-like hair that can be heat processed allowing for heat styling.
Human hair
With human hair the hair shaft is made up of dead, hard protein, called keratin, in three layers. The inner layer is called the medulla and may not be present. The next layer is the cortex and the outer layer is the cuticle. The cortex makes up the majority of the hair shaft. The cuticle is formed by tightly packed scales in an overlapping structure similar to roof shingles. Most hair-conditioning products attempt to affect the cuticle. There are pigment cells that are distributed throughout the cortex, giving the hair its characteristic color. The cuticle is a hard shingle-like layer of overlapping cells, some five to twelve deep, formed from dead cells that form scales which give the hair shaft strength and protect the inner structure of the hair. The hair cuticle is the first line of defense against all forms of damage; it acts as a protective barrier for the softer inner structures, including the medulla and cortex.
The cuticle is responsible for much of the mechanical strength of the hair fiber. A healthy cuticle is more than just a protective layer, as the cuticle also controls the water content of the fiber. Much of the shine that makes healthy hair so attractive is due to the cuticle. In the hair industry, the only way to obtain the very best hair (with cuticle intact and facing the same direction) is to use the services of “hair collectors,” who cut the hair directly from people’s heads, and bundle it as ponytails. This hair is called virgin cuticle hair, or just cuticle hair. Most human hair used for weaves and wigs is obtained from Asia (perhaps most often China, India, and Korea).