Call her old-fashioned.

“I still write with a fountain pen,” said Katy Klassman, who with her mother owns and runs a fashion boutique in Washington, D.C. “I love to go to bed early with a paper book.”

Ms. Klassman is as analog driven in her self-care routines, especially her bath.

“Maybe I’m just born in the wrong century,” she said. She remembers her grandmother bathing with an old-fashioned sponge and fragrant soap. “It was one of the things that made her for me the most glamorous woman in the world,” she said.

Ms. Klassman was talking about the kind of glamour that makes showering seem a dully perfunctory rite. Bathing, by contrast, is a steamy indulgence apt to conjure floods of cinematic imagery: Elizabeth Taylor as Cleopatra lounging in a lotus flower bath; Julia Roberts covered in suds in “Pretty Woman”; and, on the brawnier side, Sean Connery as James Bond, enjoying a loll in an oversize tub.

But glamour is only part of the draw. Baths are now touted as gadget-free zones, retreats from the sensory overload of daily life. At the same time, the tub is as often promoted as a playground, a setting from which younger fans post snapshots of themselves adrift in swirls of many-colored suds — “the symbol of self care for stressed American women,” as Fast Company put it. Those myriad selfies are but the latest indication that, for a new generation, the bath is heating up.