When graphic designer Susanna Gray started a side business three years ago turning old cashmere sweaters into mittens, she intended for her products to be used outdoors in the vicious Minnesota winter, not in the bedroom. But her husband, Jerry, had another idea.

"He said, 'Wow, that's really soft. Wouldn't that be really nice somewhere else?'" Gray recalled as she opened a plastic tub on the floor of her Sunfish Lake dining room and took out a flat piece of cardboard shaped like a phallus. Wrapped around it was a sheath of red cashmere with white trim -- a Santa costume for an intimate stocking stuffer. "Pleasure sweaters," Gray calls them.

What started as a tease morphed into Swoon, Gray's line of kinky cashmere accessories. The star product? Silky soft handcuffs with matching blindfolds -- now in demand thanks to the success of E.L. James' erotic romance series "Fifty Shades of Grey." Since the books' popularity took off this spring, Gray said, Swoon sales have tripled.

With its steamy scenes of bondage and adventure in the bedroom, the "Fifty Shades" trilogy has invigorated the publishing industry, selling more than 10 million copies in the United States and capturing the top three spots on the New York Times bestseller list. Now the sex toy industry is experiencing the windfall.

Fun Factory, the manufacturer of Smartballs -- a brand of weighted orbs that women use to strengthen Kegel muscles after childbirth -- has had to add night shifts at its German factory to keep up with a 350 percent increase in demand since a pair of the balls made a few memorable cameos in the trilogy. In New York, the Post recently reported that hardware stores are seeing an influx of new customers -- mostly women -- shopping for rope.

The Smitten Kitten, a Minneapolis sex toy purveyor, has gotten so much business since February that owner Jennifer Pritchett was able to give raises to all 10 of her employees. A prominent display in the shop features the three books, various brands of Kegel balls, whips made of leather and rubber, Swoon's restraints and masks and something called the Neon Wand, a device that emits an intense electric shock when applied to the skin. The wand retails for $189.99.

The store's general manager, Clare Jacky, said she noticed sales rising in February. "The balls, specifically, just started exploding," said Jacky. "And I read the book and I was like, 'This is definitely what it is.'" By March, she added a "Fifty Shades" page at SmittenKittenOnline.com featuring items used in or inspired by scenes in the books. By May, online sales were up 300 percent compared with May 2011.

Bondage goes mainstream

Citing a 20 percent rise in customers in the past few months, Pritchett believes the books are changing sex for couples.

"We hear it multiple times a day from different people, so excited and invigorated with the idea that we can try something new, get creative and have fun here," she said.

In August, the Smitten Kitten will offer two classes for male and female fans of "Fifty Shades" who are interested in bringing some bondage -- or at the very least, spanking -- into their love lives.

Laura Rademacher, a relationship and sex therapist, is one of the educators giving advice at the workshops. She said there is a growing dialogue among sex therapists about "Fifty Shades."

"I have a ton of conversations about this book," said Rademacher. "What's in the book, how do we talk about it with people, how do we help people be inspired by the book?"

At Lickety Split in downtown Minneapolis, manager Mark Utermarck says he can't keep the Ben Wa brand of Kegel balls, at $17.99 a pair, on the shelves.

"Women are coming in saying, 'Do you sell Ben Wa balls? Do you sell Ben Wa balls?' That item in particular seems to be the big seller. Overall I think it'll be good, loosen everybody up. Give everybody a new sexual experience instead of missionary meat and potatoes."

Dining-room-table industry

Gray, who sells her masks and restraints only at Smitten Kitten and through word of mouth, hopes that if the trajectory continues, she will finally turn a profit, allowing her to expand the business into online territory at www.swoonkink.com -- and maybe out of her dining room. (A pair of cuffs goes for $125 and the masks are $45.) Her husband has gotten in on the business, too, designing an ornately woven rattan stick for spanking that soon will be added to the Swoon line.

"I think it's really fun to have beautiful things to play with," said Gray. "It doesn't have to be scary."

For now, she will keep making the luxurious intro-to-bondage kits at her dining room table. Her next product in development is an all-cashmere whip.

Sharyn Jackson • 612-673-4260