About 18 people gathered in a semicircle inside Drybar’s new location in the meatpacking district of Manhattan. It was mid-December, and in the previous weeks they had been trained in the fine art of giving the greatest possible blow-dry. They knew how to create the beachy rumpled look of the Mai Tai blowout and the sharp, pointy, uptightness of the Straight Up; they knew how to make you look like an extra from “Steel Magnolias” with the Southern Comfort. They could twist your hair into an Uptini, if that was your need on a particular day. They knew how to turn around the salon chair with a flourish so that the customer, who up to this point had been too mesmerized by watching “The Devil Wears Prada” on a big-screen TV to notice what was being done, could see her hair, shiny and smooth, in the mirror on the wall behind her. As Drybar’s founder, Alli Webb, sitting atop the bar to greet these new employees, likes to say: “We’re not selling blowouts. We’re selling happiness and confidence.”

The next day, this new Drybar would open. All the appointments — 200 blowouts — had been booked for days. This was Drybar’s 39th store. It would open its 40th within just a month, on the Upper West Side. A blowout is a diabolically ingenious product: it can be undone and destroyed simply by adding drops of water. The top three blow-dry chains — Drybar, Blo and DreamDry — have more than 100 locations in the United States so far. As recently as 2007, there was not even one. The feeling of “happiness and confidence” that comes with smooth hair is real, but it creates its own self-perpetuating need.

Ms. Webb didn’t invent the modern blowout, but Drybar is the largest chain in the United States. Its growth suggests something of a holy war on frizz, one neighborhood at a time.

Ms. Webb, who is 40, came to Manhattan from Irvine, Calif., where the company is based. She attends all of the store openings, to meet the new stylists, tell the origin story of the company and relate to them how badly she wants Drybar to keep its mom-and-pop feel. She sat cross-legged on the bar — that’s the counter where women sit to have their hair blown dry; everything in Drybar, from the coaster gift certificates to the Happy Hour shampoo is real bar-themed — and began by asking the new stylists what they would have been in another life. One woman, who would have been a “celebrity stylist and/or a ballerina,” came to Drybar because she had worked at a salon that forced its workers to wear khaki pants and white button-downs and where stylists weren’t permitted to talk to one another on the floor. At Drybar, you can talk to your co-workers, and you can wear anything, as long as it’s black or white or yellow or denim.