Question: How do memory-foam mattresses differ from innerspring mattresses?
Answer: Inner-spring mattresses account for more than 90 percent of wholesale mattress sales in the United States, according to the International Sleep Products Association. They contain a network of coils or springs, clad in layers of padding. Foam mattresses have no coils, although there are several types of foam, each with a different density.
Memory foam, or viscous polyurethane foam, is a heat- sensitive, man-made material that eases pressure points. It was developed for use in space, to protect astronauts...