Stylists apply a keratin-rich solution to the hair’s second layer for a straighter and smoother look that can last for up to twelve weeks or longer, and, although any heat-based treatment can be taxing on hair, its fortifying effects tend to leave hair glossier and more voluminous than other relaxers do. So although frizz disappears, waves or loose curls can continue to cascade across the shoulders. The express treatment lasts 4-6 weeks.