MEMPHIS -- Dick Roberts considers himself a hard-working executive, but he always has time to work on his tan. He heads from the office at midday for a comfortable tanning room, where he sleeps on a thick mattress while fake sunlight warms his skin.

For 30 blissful minutes, an odd-looking sunlamp showers Roberts with tanning rays so strong that it takes just 6 minutes for him to get an hour's worth of sun. "It's very relaxing," says the 38-year-old executive with obvious satisfaction, "especially after a big lunch."

This is not any ordinary tanning studio. Roberts soaks in his sunshine at the tanning labs at Plough Inc., the company that makes Coppertone, Shade and Tropical Blend suntan lotions.

It is here in Memphis that laboratory scientists in white coats mix chemicals with such tongue-twisting names as homosalate, sorbitol and carbomer 941 into goos and gels. In scientific doses, researchers smear secret tanning formulas on volunteer sunbathers like Roberts, a Plough scientist, who then spend carefully timed minutes under the "solar simulator." Across the room, greased-up swimmers, hired to check whether an experimental tanning potion is waterproof, swish in a whirlpool.

Other scientists are assigned to tinker with the way a concoction feels and smells so that sun worshipers will want to rub it in deep. The research goes on in university laboratories as well. At the University of California, Los Angeles, for instance, scientists under contract with Plough are blasting shaved mice with UVB and UVA rays, the kind that make sunbathers burn and tan, in the search for sunscreens.

It is all part of Coppertone's search for the ultimate tan -- a search that begins in the antiseptic laboratories of Memphis and ends up on America's sandy beaches.

Such research efforts may seem extraordinary, but to Plough and other companies that make suntan lotions, lots of money is at stake. This year, Americans are expected to spend more than $350 million on tanning lotions, gels, oils and mousses, and millions more on such extras as cocoa butter, tan accelerators and sunburn salves.

Mounting evidence that links sunburns to skin cancer and unsightly wrinkles is slowly changing the complexion of the tanning industry.

Far from killing an industry based on sunshine, the concern about cancer has only given Coppertone and its rivals dozens of new products catering to the careful. Aging baby boomers, who as teen-agers covered themselves with baby oil, are stocking up on sunscreens that block the sun's harmful rays. Yuppie parents are increasingly slathering sunscreens on their children to prevent them from frying.

Drugstore shelves are brimming with the results of research at Plough and other companies. There are sun blocks for noses, lips, faces and bald spots. There's an "Anti-Wrinkle Sun Creme" and an "Ultra-Protection Skin Cancer Garde." Aramis promotes a three-step "man's approach to tanning" and Sea & Ski says it has a package of products that slowly "turns girls to gold."

Firms such as Estee Lauder and Lancome "are riding the carcinogenic wave" to bigger profits, says cosmetic industry consultant Allan G. Mottus. He estimates that sales of department store brands are gaining by 20 percent a year, while drugstore brands such as Coppertone are chugging along with a 5 percent growth.

Once Coppertone told sunbathers: "Don't be a paleface." Now one Coppertone advertisement features a pale, skin cancer victim who urges consumers to use one of the company's sun blocks.

"What is the perfect tan?" asks Anthony Guiliano, who as Coppertone's marketing vice president spends a lot of time considering the question. Teen-agers still want deep dark tans because "it makes them feel attractive; it's part of the dating game." But for most people "a perfect tan is sort of a gold," he says.

As the biggest company in the business, Plough does more research than anybody else. Since 1976, 10,000 volunteer sunbathers got tans under Coppertone's solar simulator in Memphis.

The quest for the perfect tan centers on a small laboratory that looks like a doctor's office. The walls are hospital white. Drapes surround the area where volunteer sunbathers rest under the "solar simulator." Old magazines are stacked high for visitors to read.

"It can get pretty boring," says laboratory technician Phyllis Hinkle.

At the far end of the laboratory is a 240-gallon whirlpool that's used to test waterproof suntan lotions.

The big attraction is the "solar simulator," actually a high-power sunlamp that closely resembles an X-ray machine. On this day, Mary Robinson, a 56-year-old volunteer sunbather, rests on a stretcher underneath the odd-looking sunlamp. She wears a white hospital gown, but the back is open.

Robinson, who says she prefers air-conditioning to sea breezes, admits to feeling a little apprehensive. "I think it'll be OK," she says.

She is about to find out. Using a ballpoint pen, Hinkle draws a square on Robinson's back. Next, Hinkle takes a syringe filled with exactly 100 milligrams of white lotion and squeezes it onto Robinson's back. As Hinkle smoothes the lotion, Robinson winces -- it is cold.

"Now don't move," says Hinkle, sounding like an X-ray technician. She turns on the sunlamp, which showers Robinson with rays 10 times more powerful than the sun. The lamp shines for 12 minutes -- equal to two glorious hours at Malibu. But Robinson's back still looks white. "I don't feel a thing," Robinson says.

Robert M. Sayre, Plough's director of photobiology, says most people don't feel anything because the sunscreens being tested are pretty powerful. At most, people get a few pink blotches that fade in a day. "This isn't a good place to get a tan," he says.

Before Plough got its solar simulator, everyone got tan -- even burned. Volunteer sunbathers were led to the top of Plough's roof, where they spread beach towels and baked in the hot Memphis sun. It was a great way to get a tan, but it wasn't very scientific; a sudden thundershower could ruin a whole day of research.

The swimming test in the days before the whirlpool were also pretty realistic. Swimmers were treated to an all-day pool party at a nearby Memphis home. After covering themselves with lotion, the volunteers swam laps and bobbed in a large pool. But this system had its drawbacks. "Some of these people never told us they couldn't swim," says Sayre.

Sunscreens have come a long way, too. Although the chemicals have been around for years, the early formulas are what marketing executives politely call "cosmetically inelegant."

Hawaiian Tropic's first sunscreen was goo that contained dark brown petroleum jelly. It blocked the sun fine, but "it felt sort of funny on the skin," says Jack E. Surrette, marketing director for Hawaiian Tropic, the No. 3 tanning company.

In the early 1970s, Coppertone came up with a sun block that only worked in an alcohol solution. The formula kept sunbathers from burning, but it also dried their skin and smelled like medicine.

The big breakthrough came several years later, when researchers discovered a group of chemicals called paba esthers. These chemicals blocked the sun and didn't need to float around in alcohol to work.

Scientists still use these chemicals in sunscreens. In fact, the Food and Drug Administration has approved 21 sunscreen chemicals.

The FDA also enforces a rating system that measures a sunscreen's effectiveness. The rating scale goes from zero to 15. A "sun protection factor" of 15 means that it will take a user 15 hours to get the burn that he would normally get in one hour.

Because the FDA regulates the process so closely, there "is no difference" in the way products with the same rating guard against sunburn, says Michael Caswell, director of skin biology research at Coppertone.

The result is that tanning lotions mostly differ "in the way they feel and smell," says cosmetic industry consultant Mottus.

Researchers compete fiercely to be the first with new developments. Sayre remembers when rival Johnson & Johnson came out with the first waterproof sunscreen -- its Sundown lotion.

"We went crazy around here," he says. "We got their lotion into the lab and took it apart to see just how they did it."

According to federal regulators, sometimes the results of all this tanning research goes a little overboard.

The federal agency says that products with sun protection factors above 15 are little more than marketing gimmicks since they don't offer consumers much more protection.

Coppertone has two lotions with a 25 sun protection rating; Estee Lauder has the highest with a 34.

"There really isn't enough time in the day to benefit from a lotion with a 25 rating. The day is only 24 hours long and the sun is shining for even less than that," says Heinz Eiermann, director of colors and cosmetics at the FDA. "It's really gilding the lily."