Mary-Kate and Ashley Olsen's Hairstylist Reveals Secret to the Sisters' Signature Waves and How Their Hair Differs

Mary-Kate and Ashley Olsen are, fashionably speaking, known for two things: good style and good hair.

For decades, The Row designers, both 38, have made a mark on the beauty industry for their signature looks, particularly their wavy hairstyle, but it turns out, its staying power didn't happen overnight.

Celebrity hairstylist Mark Townsend, who's been working with the Mary-Kate and Ashley for over two decades, revealed how he's perfected the effortless look on an episode of the Gloss Angeles podcast released on March 14.

He began by saying that Mary-Kate and Ashley's glam prep has changed "so much" over the years. "It used to be a fight of who sat in my chair first. They would sit down soaking wet hair, get that full blowout, then go back with the iron, never open the clamp just wrap it around," Townsend explained, adding that dry shampoo on the roots and a salty spray, serum or cream on the ends would be necessary to create the style.

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"Then they started getting into air-drying, then the fight always became about who would have to come to me first," he said. One of the times he applied the no-work technique was, surprisingly, during the 2013 Met Gala.

He remembered Ashley, who wore an intricately made orange vintage Dior gown, wanted to do the bare minimum with her hairstyle, meaning no tools or heat. Townsend's alternative was simple, but made an impact. "I set her hair with clips and let it air-dry and it turned out so perfect."

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Despite doing almost the same exact hairstyles for the siblings, Townsend revealed that the two actually have very different hair textures. "They have such different hair, I approach it completely different. I use product for each one. Ashley's hair is much curlier and much darker, but Mary-Kate's is a little bit more coarse."

In 2013, Townsend spoke with PEOPLE about collaborating with the pair. “They have such amazing style, it is so inspiring. And it so personal,” he said. “They don’t follow trends — they are usually setting them — so they do what works best for them, what looks best on them and it’s the same with their hair."