The image of a mother seated in a rocking chair, lulling her baby to sleep with a comfortin to-and-fro motion, exudes warmth. A rocker beside a blazing fire or welcoming visitors to a front porch is classic Americana. Among the most democratic pieces of furniture, rockers have been welcome everywhere from the humblest homes to the White House.
John F. Kennedy made his rocker famous when he installed it in the Oval Office to ease his ailing back. Jimmy Carter brought five of his Jumbos (a rocker style designed by Thomas Brumby in 1875) to Washington. Abraham Lincoln enjoyed his until the day of his assassination on April 14, 1865. He was sitting in his upholstered rocker at Ford's Theater when John Wilkes Booth fired the fatal bullet.
"For more than two centuries Americans from all walks of life have been rocking, dozing, dreaming, reading, nursing, spinning tales and orating from rocking chairs," writes Bernice Steinbaum in her book "The Rocker: An American Design Tradition" (Rizzoli).
The rocker's old-fashioned, homespun image conjures up in many the feelings of family. Ms. Steinbaum believes its symbolism is even more profound.
"Rocking chairs are for dreams and dreamers," she said recently. "They're the place we most associate with life and death, from the cradling of the baby to the rocking in our sunset years. Yet we can enjoy rocking chairs at all ages. The rocker is the most likely piece of furniture to pass down. We all want a piece of yesterday so we can have some tomorrow."
Psychology and nostalgia aside, there appear to be some physiological benefits to rocking as well.
"Any time you recline, the muscles of the back work a lot less hard than when you're sitting up straight," said Christen Grant of the University of Michigan Center for Ergonomics in Ann Arbor. "When you recline, you're more balanced. Also, you put less weight and pressure on your discs than when you sit up straight.
"The core of the discs is alive, but the core is surrounded by tough fibrous rings. Past adolescence the blood supply diminishes and probably starts to shut down when you're in your 30s. When you sit in a rocker, you're constantly compressing and decompressing those discs. It follows that the core of the discs [is] better fed.
"Finally, you use your feet or legs for the rocking motion. This stimulates blood circulation."
Just who conceived the idea of a rocking chair is unknown. Benjamin Franklin often is credited with inventing the rocker, but its origins more likely are European. "The rocker probably was adapted from a baby's cradle," Ms. Steinbaum said.
One classic style that many American furniture companies still manufacture is the bentwood rocker.
Designed in 1860 by Michael Thonet, a German cabinetmaker living in Vienna, the rocker's form was innovative. Steam-shaping the wood allowed the arms to arc from the oval rattan back to join the deeply curved frame, which in turn continued seamlessly into the bottom skate (rocker). A scroll decorated the sides.
The Bentwood Model 2825, manufactured by Thonet Industries, measures 43 inches high by 23 inches wide by 40 inches deep, with a 17-inch-square seat.
Other classic designs remain popular. There are interpretationof the Windsor rocker, adapted from the English chair that dates to the 17th century. Some of these are painted with floral motifs, stenciled or sponged, as were the originals.
The simplicity of Shaker rockers has captured a 20th-century audience because they bridge modern and vintage architecture, country and urban interiors. The spare and familiar silhouette, with slat backs, rounded finials and rush or woven seats, has been interpreted by any number of manufacturers.
The Victorian fondness for wicker chairs, settees, tables and planters led to the design of rocking chairs in that medium. Many examples at the turn of the century were quite elaborate, detailed with curlicues and cuts. Today, more unadorned designs are being reproduced to reflect modern tastes.
Rustic country styles for front porches and outdoor decks include delicate twig styles naturally finished or painted. A rustic twig rocker, like one made around 1915 in West Virginia that is now is part of a collection at the High Museum of Art in Atlanta, suits a contemporary setting quite well. Such twig rockers still are being made. At least four styles of hand-made hickory rockers are produced for the Amish Country collection in New Castle, Pa. The average price is $300.
Barbara Goodman and her husband, Eric, sell hand-crafted teak or Honduras mahogany furniture suitable for outdoor use through their mail-order catalog, Wood Classics. They long have harbored a love affair with the rocker. "Rockers speak to our emotions," said Mrs. Goodman. "They evoke images of tranquillity and warmth. In our house, it never fails. People go straight to the rocker."
Many styles of rockers are available, but clearly the design cannot be adapted to some periods. Think of how odd, for example, a gilded Louis XV frame might appear with skates.
Ms. Steinbaum included some exotic images in her book and in an exhibit that she held in her Soho art gallery in 1989. Jeweler and product designer David Tisdale was invited to participate. He drew from his own reminiscences and teamed those with familiar working materials: stainless steel, anodized aluminum (anodizing changes the color) and stained wood.
Mr. Tisdale believes it's the interactive nature of rocking chairs that keeps them popular.
"There's a response you have with the rocker," he said. "There's an energy that comes out of it. You have to keep using your muscles to push it. I don't know anybody who doesn't like rocking chairs."
Some early rockers sit so low to the ground that you can't get up without feeling as if you have to be pried out.
There are no rules for designing a rocking chair, and there's little advice about how to select one.
"The chair needs to fit your body," said Walter Kleeman, an ergonomics consultant, interior designer and author based in High Point, N.C. "You accomplish this with an adjustable back or with the size of the chair.
"To fit 99 percent of Americans you must have a seat width of at least 21 inches between the arms. With the depth, you get into some problems because of the weight of the thigh and length of the leg, which vary so much from person to person. If you make the rocker seat too deep, a lot of people have to sit toward the front of the chair, or their legs will be sticking up."
"A deep seat puts pressure on the back of the legs," said Christen Grant of the Center for Ergonomics at the University of Michigan. "Smaller people can't reach the back of the chair and their feet won't touch the floor. It's important to scooch all the way back and not be pressed against the front end of the seat."
Pitch also is important. "If the seat is too flat or horizontal, whenyou're leaning back, you'll tend to slide out, especially when you sit forward," said Mr. Grant. "That's uncomfortable. And it's tiring to make your feet work too much.
"The way a seat tilts back to prevent sliding is called sheer. Where the seat and back come together should be more than 90 degrees -- 100, 120 or even 135 -- for the health of the lower back. It has to do with the shape of all the vertebrae in the back. When you stand, the back is in a curve, pressure on the discs evenly distributed. When you sit in a 90-degree position, your lower back gets flat. As it flattens, it smooshes the front part of the disc.
"With a good rocking chair, you rock not just by pushing with your feet, but by shifting your center of gravity."
So selection of a rocker is as subjective as choosing a mattress or a pillow for your bed. It depends on your size, the way you sit, and your weight distribution. You have to try it out.
"Some people like their backs prone," said Bernice Steinbaum, author of "The Rocker: An American Design Tradition."
"I like to sit straight up. Some like bars in the back, whether they are flexible or not. Some like the sense of wood touching their backs, others like their backs upholstered."
* Amish Country Collection, R.D. 5, Sunset Valley Road, New Castle, Pa. 16105; (412) 458-4811
* Ethan Allen Inc., Ethan Allen Drive, Danbury, Conn. 06811; (203) 743-8000
* L. L. Bean Inc., Casco Street, Freeport, Maine 04033-0001; (800) 221-4221
* Ilana Goor, 979 Third Ave., Suite 240, New York, N.Y. 10022; (212) 421-9114
* Thos. Moser Cabinetmakers, 72 Wright's Landing, P.O. Box 1237, Auburn, Maine 04211-1237; (800) 862-1973
* Stickley Furniture, 1 Stickley Drive, Manlius, N.Y. 13114; (315) 682-5500
* David Tisdale Inc., 16 Waverly Place, New York, N.Y. 10003; (212) 228-7363
* Thonet Industries, a division of Shelby Williams Industries Inc., 1348 Merchandise Mart, Chicago, Ill. 60654; (800) 551-6702
* Wood Classics Inc., Osprety Lane, Gardiner, N.Y. 12525; (914) 255-7871. Send $2 for a catalog.