Hair extension

Hair extensions (or artificial hair integrations) are pieces of human or synthetic hair that are added to a person's own hair to change its length, texture, body, or color.

Human extensions are natural hair from humans and are classified by ethnic origin. Synthetic extensions are man-made of fibers such as Kanekalon and Toyokalon.

Types

Weft or track: Human or synthetic hair is bonded by machine or hand-sewn to thin pieces of ribbon or itself at the top. They are generally available in strips of 42 inches wide, with lengths of 14-26 inches and can often be cut into smaller sections to use in weaved or crocheted styles.
Bulk: Human or synthetic hair is not bonded together, but rather bonded directly to a person's hair to create loose extensions or braids.
Hair pieces: Human or synthetic hair is pre-formed into a style that can be worn over a person's hair (as in a wig) or temporarily attached to existing hair to form a ponytail, bun, or up-do.

Application

Bonding: Bulk or weft extensions are permanently attached by using special adhesive to glue the new hair to the existing hair. A patch test is usually recommended before attachment to rule out sensitivities or allergies to the adhesive.
Sewing: Weft extensions are permanently attached by using a special needle and thread to literally sew the new hair into the existing hair. This is usually done with tight, intricate hair styles such as cornrows. The high tension has the potential to cause gradual hair loss.
Clip-in: Hair pieces are temporarily attached with a clip or comb, resulting in the least amount of damage. Clip-in extensions can be a less expensive do-it-yourself alternative to salon application methods.