What is the characteristic shape of a concave perm rod?

The characteristic shape of a concave perm rod is smaller in the center. This design allows the hair to wrap around the rod in a manner that creates a tighter curl at the center. The tapered shape, being wider at both ends and narrower in the middle, provides varying degrees of curl along the length of the hair. This variation contributes to more dynamic and textured curls, resulting in a hairstyle with depth and movement.

The unique concave shape promotes an even distribution of hair around the rod, which results in a more defined curl at the center and looser curls toward the ends. This shape is particularly effective for creating volume and body in the hairstyle, making it distinctly suitable for achieving the desired wave or curl pattern desired in cosmetology applications.