A simple box of cardboard, foil and glass is being promoted as a means to free Third World women from the time-consuming search for firewood and get them out of the unhealthy smoke of wood cookfires.

The solar cookers, designed by two Arizona women, are being introduced in the Third World by Pillsbury Co. "We feel the potential of solar cookers is so great that it could truly alleviate some of the global problems," said William H. Sperber, a senior research microbiologist at the food conglomerate.The United Nations estimates 1.5 billion people are affected by firewood shortages, said Robert Metcalf, a microbiologist at California State University-Sacramento who attended graduate school with Sperber at the University of Wisconsin 20 years ago and is working with Pillsbury.

"They've got a lot of sunshine, but they don't know how to use it," Metcalf said. "It's fun in the United States, it can be very useful, but it's critical in developing countries."

The cooker is an insulated box within a box topped with a glass pane and a reflector that directs sunlight. It can be made out of cardboard or wood, and aluminum foil. Food is cooked in dark, covered metal, glass or ceramic pots.

The temperature peaks at 250-275 degrees, meaning food takes longer to cook than in electric ovens. But Metcalf says users save time by no longer having to collect firewood and by not having to stir the food because of the low heat.

Metcalf, who has been promoting the solar cooker since 1979, was joined by Pillsbury in 1986. He and Sperber have demonstrated it in Africa and South and Central America. Pillsbury is spending more than $100,000 on the program.

Simplicity may be an obstacle to widespread adoption, supporters say.

"It doesn't look as high tech as other things that have been tried," said Chris Flavin, vice president of research at Worldwatch Institute, a private non-profit research group that focuses on global resource issues.

"There's an actual bias in development agencies against anything that's small and decentralized," said Flavin. "They like to support big projects because they're easy to manage."

Flawed cookers produced before the Arizona women designed theirs also have discouraged widespread use. They tipped easily, temporarily blinded users, had reflectors that fell off and were able to cook only one pot of food at a time.

Barbara Kerr of Taylor, Ariz., a nurse, and Sherry Cole of Tempe, a former free-lance writer and neighbor of Kerr's, created the design in the mid-1970s. Since then, Cole said, they've sold about 3,000 kits and cookers ranging from $40 to $275 and several thousand plans, from $1 to $3.75.

Sperber and Pillsbury became involved in 1986 while working in Bolivia with the Freedom from Hunger Foundation, a private, nonprofit group, on the problems of lack of firewood, high infant mortality and diarrhea. Metcalf and scientists from Pillsbury's Technology Center have worked to simplify the design so it can be better mass produced and more easily assembled in the field.

By trial and error, Metcalf and his family have developed recipes that work with the cooker. Vegetables, which contain moisture, don't need to be cooked in water, they discovered after one "soggy mess." Chicken can be cooked in three hours but can't be overcooked because the low temperature won't turn moisture in the food to steam, dry out the food and burn it. The normal amount of water is added to dried grains, such as rice, and to beans.