The Cambridgeside Galleria offers a lot of places to spend money, from stores to restaurants to a car wash — the Dr. Detail full-service car wash, which operates out of the mall's parking garage.

"It's a nice amenity that we can offer our customers," said Jennifer Rotigliano, senior marketing director for the mall, in Cambridge, Mass.

Car washes while you shop. Car washes that come to your home or business. "Greener" car washes. Softer cloths. Better computer technology.

These are among the latest developments in the long, sudsy history of the car wash.

The earliest car washes were simple affairs — "the days of the sponge and bucket," as the International Carwash Association calls it. Then conveyers — initially just a chain hooked to the front bumper — pulled the car through the wash. Early conveyer operations still had people washing the cars; later, mechanized operations became the norm.

Today's mobile car washes often mean a return to washing by hand.

"There's no automated system," said Eric Goodman, owner of Dr. Detail.

Goodman started out with a mobile carwash van in Miami, then moved his business to the Boston area. Operating out of a mall, he said, was a perfect fit for a year-round operation. His charges range from $14 for the exterior, rims and wheels to $159.99 for the full "soup to nuts."

The vast majority of the country's 75,000 car washes are either in-bay automatic facilities or self-service ones, according to Eric Wulf, executive director of the carwash association. In-bay facilities are commonly found in gas stations. You pull in and your car remains stationary while the equipment moves around it, Wulf said. At self-serve spots, customers use equipment in the bays.

About 20 percent of car washes use conveyers, he said. "The car moves and the equipment remains stationary."

Which type of wash — hand or machine — cleans better? It depends who you ask, and also on a variety of factors including time, convenience and how dirty the car is.

"It's very common for a car wash customer to get a full service, inside, outside and underside, every third wash," Wulf said. In between, he said, they may opt just for an exterior wash.

Steve Harris, owner of the Mr. Wash shops in Washington, D.C., and its suburbs, prefers the machinery "because it's more consistent."

But Edward Rogers, who has worked in the mobile car wash business in the Atlanta area, disagrees. "A hand can get to places that a machine can't get," he said. "You're able to actually press down and wipe."

Car washes in mall parking lots allow people to multitask. Goodman said his customers often go shopping and have lunch while their car is being cleaned.

Even mechanized car washes require human beings to vacuum the car or clean the inside of the windshield, among other things.

Over the years, car wash equipment and materials have changed to clean better and protect cars' paint. One significant development, according to Wulf, was replacing nylon bristles with soft synthetic cloths.

And Wulf said car washes now use more biodegradable soaps and chemicals. Some also use a closed water system, so the water is recycled.