When Robin Macy spotted a NOFX concert T-shirt featuring a pair of pretty girls, she had an idea where the design would look best: on a bikini bottom. As the CEO and founder of Vin-T Bikini, Ms. Macy has made a business out of turning vintage T-shirts into eye-catching swimwear.

“I didn’t even know who NOFX is, but it was the craziest shirt I’ve even seen,” she said. “I just had to buy it. I thought, ‘This is going to be a fun bikini.'”

Ms. Macy, who is from Arizona, arrived at the idea for her company in 2006, as she was cleaning out her closet.

“I was throwing out T-shirts and my younger brother said, ‘Wouldn’t it be cool if someone made these into bikinis?’ The next day I went out and bought a sewing machine.”

It took five months of trial and error before she created her first form-fitting, chlorine-proof prototype out of a Harley Davidson shirt.

“If I don’t cut it right, then you get in the water and it’s going to sag,” she said. “It also took a long time to get the right lining to keep the T-shirt together. I’ve been in the shower so many times with a bikini, just to get it right.”

Ms. Macy launched the company last December, and so far, it has raked in $10,000, selling on average two pieces a week. The pieces cost anywhere from $135 to $398, depending on the original shirt’s value.

Ms. Macy, who worked in insurance before launching the company, selects shirts with simple but attractive logos, anything from Bruce Springsteen to the New York Giants to Arizona State University’s Sun Devil mascot.

“I look for anything that has a little innuendo, something sexy or fun,” she said. Because her pieces are one-of-a-kind and not mass-produced, she doesn’t have to worry about copyright infringement.

Ms. Macy traces and cuts each shirt into bikini pieces herself, before cutting matching shapes out of absorbent fabric, later used to line the T-shirt pieces and make them waterworthy. She then sends the pieces to a pattern grader in the Garment District, who sizes and labels the swimwear according to national standards. Finally, each piece is sent to a Brooklyn factory for the final touches, where strings are attached to string bikinis, and the lining is double-stitched into the T-shirt material.

Because the top layer of the bikini is T-shirt fabric, the bikinis “fit just like a panty,” she said, adding, “I treat it like a T-shirt [and] throw it in the dryer.”

A neighbor of Ms. Macy’s, Lisa Baruch, recently wore a suit while on a visit to Miami’s Shore Club hotel, where “I got a lot of compliments. It’s so unique, even in a hot scene like that it really stands out.”

As word catches on about the suits, Ms. Macy is working to develop her clientele. Most recently, the drummer for the pioneering punk band The Ramones, Markey Ramone, requested three bikinis for an auction that will be part of his launch of a condom he is producing with safe-sex education company Ready Two Go. She has received 50 requests so far from customers asking for individually tailored designs.

“Some of the requests I can’t do,” Ms. Macy said. “I didn’t know a triple-D existed until last week.”

Her designs are carried in the Beverly Hills Bikini Shop in Los Angeles, and Hotel Scottsdale in Scottsdale, Ariz.; about 30% of her sales come from New York.

With the summer buying season in full swing, Ms. Macy is seeing an increase in business, especially in New York. She regularly promotes her pieces at monthly pool parties held at Hotel QT at 125 W. 45th St., and is hopeful the hotel will begin carrying some of them.

“People really like her lines,” Andrew Lockhart, the director of boutique consulting agency projekt:nyc, which co-hosts the monthly pool parties, said. “They’re custom pieces that no one else is wearing. That’s a lot of the appeal of it, the fact that every one is one-of-a-kind.”

Ms. Macy, who took out a loan to launch her company and operates out of her apartment, was given approval to mass-produce copyright designs last April, but plans to wait until next year before expanding her operation.

“The funding has been completely me, which has been extremely difficult,” she said. “The problem now is all of a sudden, production costs have doubled for everything. Everyone in the industry has been affected.”

Despite the challenges, Ms. Macy is optimistic about her foray into fashion.

“I’m a mom,” she said. “I never thought I’d be doing something like this. I just landed into it and it became my second baby.”