Anyone who’s ever put their hair up in a high ponytail or slicked-back bun knows the struggle with erratic lumps and bumps. You take your hair down, smooth out the lumps and put it back up again — ...

A loose, informal chignon with loopy tendrils is one thing. A lumpy ponytail, with one section pulled out of the clasp so it rises up greasily and asymmetrically is another. This scourge of girlhood ...