What can be a result of under-processing hair during the perm application?

Under-processing hair during a perm application leads to the hair remaining straight because the chemical process necessary for the perm to take effect has not been completed adequately. When hair is not processed long enough or the perm solution is not applied thoroughly, the hair strands do not absorb enough of the chemicals needed to break down the disulfide bonds in the hair structure.

As a result, without proper bonding alteration, the hair fails to achieve the desired curl or wave pattern, and instead retains its natural straightness. This can be particularly frustrating for stylists and clients who expect a transformation in hair texture. Instead of enhancing the curl formation, under-processing halts the chemical reaction prematurely, resulting in a lack of the intended curl pattern.

The other options, while they describe issues that can occur during or after a perm, do not relate directly to the effects of insufficient processing time or concentration. Overly tight curls, frizzy texture, or dry hair would typically stem from over-processing or inadequate technique after the hair has been sufficiently relaxed or curled.