Melissa McCarthy wants to change the way clothing is sold.

That might seem like an odd goal for the movie star and comedienne, who's starring in the new comedy Spy. But McCarthy comes from a fashion design background: She studied clothing and textiles at Southern Illinois University, then moved to New York City to study at Fashion Institute of Technology. Then a classmate suggested McCarthy perform at an open mic night, and that was that.

Then, preparing for the 2012 Oscar ceremony, McCarthy was unable to find a designer willing to make her a dress worthy of the red carpet. Designing her own line suddenly seemed a bit more urgent. After about four years of development, Melissa McCarthy Seven7 is due to launch at the end of the summer, when it will be available online and in stores including Macy's, Lane Bryant, and Nordstrom. McCarthy will start by introducing sportswear ranging from $54 to $159.

Unlike most mainstream designers, McCarthy is going to be releasing clothes in sizes 4 to 28. Her goal is to get stores to sell all of them in the same location, rather than sending some customers to the plus-size department or online to find the same clothes that their friends are buying in the main section of the store.

"I think it's strange to segregate a part of the population and put them somewhere else," she says. "I think it sends a negative message, and I'm looking forward to the first store that's going to [change] that. That would be monumental. That's a big part of what I'm trying to do."

McCarthy pointed out that the best-selling women's size in the U.S. is a 14, yet many mainstream retailers top out at size 12. Part of the problem, she says, is that most retailers aren't set up to show a full range of sizes in one place--yet.

She still has work to do on that point: Macy's and the other retailers that have agreed to pick up her line initially will be carrying the so-called "plus" sizes, while the smaller sizes will be available online. When asked how she'll persuade retailers to make the investment to carry the full range of sizes, McCarthy says, "The proof will be in the pudding later if it sells."

McCarthy, whose new movie opens Friday, was enthusiastically showing off samples at a hotel suite in New York this week. (No pictures of the clothes are allowed until the actual launch.) She spoke with me about how she created clothing she'd like to wear, during a time when she was becoming one of Hollywood's busiest, funniest, and most bankable stars.

Finding--and dumping--a partner

This is actually McCarthy's second attempt at launching a line of women's clothes. Her first manufacturer turned out to be a poor choice, she says. When McCarthy saw its first samples, she says, the manufacturer had basically ignored all her input, and made clothes based on its own preconceptions of what plus-size women want to wear.

The fabrics, she says, were "really bad. It didn't drape, and you saw every possible imperfection. A little better fabric, it's like good lighting--it's like magic." 

Most of those early samples were also sleeveless, which was not at all what McCarthy wanted. The manufacturer told her that plus-size women didn't want sleeves. "First of all, you can't say, 'Women don't want fill-in-the-blank,'" she says. "You can't make generalizations like that, that's very strange....It was like, 'Thank you very much, we've all done months of work, for absolutely nothing.'" 

By contrast, McCarthy describes her current manufacturer, Sunrise Brands, as "wildly collaborative," and admits that Sunrise is "probably shocked" by how involved she is. She makes sketches for all the clothes, and says that she's lucky enough to also work with "someone who sketches much better than I do."

She goes to every fitting, reviews every sample, and wears every garment for a day. "I want to make sure," she says, "something doesn't pull, that there's not a weird waistband, that the skirt doesn't ride up." She's adamant that women enjoy her clothes; if someone bought something because McCarthy had said she thought the customer would like it and then did not, McCarthy says, she'd feel "terrible."

"I want to put something positive out into the world," she says. "If it's not positive, what's the point?"

I ask, Is that why she's in comedy? McCarthy looks surprised, then shrugs: "Maybe."