You're preparing for a party or a family gathering. You've invited the guests and planned the menu. You take out your finest utensils and serving pieces--then let out a loud groan. The silver is badly tarnished. It's time to tackle one of the holiday season's least popular traditions: cleaning and polishing the silver.

Many people just reach for a commercial product and start rubbing. But Jerome Kruger, a professor of materials science and engineering in the Whiting School of Engineering, says a simple home recipe using baking soda, water and aluminum foil can remove stubborn stains from silver with minimal muscle power. He says this method is particularly helpful in pulling tarnish from narrow grooves and intricate patterns--places that are hard to reach with traditional cleaning methods.

Do try this at home: All you'll need to clean your tarnished silver, says Jerome Kruger, a professor of materials science and engineering, is aluminum foil, baking soda and water.

Kruger is an internationally respected expert on corrosion, and tarnish--like its cousin, rust--is a product of the corrosion process. In fact, the term is derived from a Latin word for "gnawing," the same root that produced "rodent."

"Corrosion is the deterioration of a material, usually a metal, as a result of chemical reactions with the environment in which it is placed," Kruger explains. "Tarnish is produced when silver reacts with sulfur compounds in the air, such as the gas released when you boil eggs. Tarnish doesn't harm the metal. It's just ugly. Silver pieces are supposed to be bright, shiny and lustrous."

To remove tarnish, Kruger triggers another chemical reaction that separates the sulfur from the silver. Here are the four easy steps:

1. Wrap the entire silver object in aluminum foil. Be sure the foil makes tight contact with the silver in at least one place. Make a few cuts in the foil to allow liquid to seep into the space between the silver and the foil.

2. Place the foil-wrapped object in a large glass, enameled or stainless steel pot that can be placed on the stove.

3. Fill the container with a solution of water and 4 to 5 tablespoons of baking soda (sodium bicarbonate) per quart of water. Use enough water to cover the silver object. Let the mixture simmer gently for 30 minutes.

4. Remove the aluminum foil. Rinse the silver and dry it thoroughly.

The tarnish in the cracks and crevices should be removed by this procedure. If not, repeat.

Although commercial silver polish products will also remove tarnish, they usually require more scrubbing. "The tarnish in the grooves is very hard to remove with commercial cleaners," Kruger says. "The reason that this process works so well is that it acts electrochemically. There is a flow of electrons between the silver object and the aluminum foil, and that's what removes the tarnish."

The electrochemical process may not entirely restore the original gleam, Kruger cautions. People who want some extra sparkle may choose to apply a small amount of commercial polish to the broad, smooth surfaces of the silver piece.

Kruger first circulated this tarnish removal recipe in a consumer cleaning tips pamphlet produced by the federal agency now known as the National Institute of Standards and Technology. He was employed by that agency before joining the faculty at Hopkins.