The Baking Soda and Foil Bath for Silver: How It Works and What to Keep Out of It

Of all the kitchen tricks for jewelry, the foil bath for silver is the one with real chemistry behind it. Lay a tarnished chain on aluminum foil in hot baking-soda water, and the black tarnish is turned back into silver.

In this guide I'll show you how it works, what museum conservators say it costs, and the pieces that should never go in the bowl.

What tarnish is, and why there's no hurry

The Canadian Conservation Institute (CCI), the Government of Canada's conservation agency, explains that tarnish is mainly black silver sulphide, caused by sulphur gases such as hydrogen sulphide in the air. They come from air pollution, certain foods, rubber, some paints, and wool or felt.

Winterthur Museum's conservators say tarnish is not damaging to silver. As a Johns Hopkins professor put it, "Tarnish doesn't harm the metal. It's just ugly." So you never have to rush.

And wash first. Grease and grime aren't tarnish. Winterthur says silver can be safely washed in water with a few drops of gentle, unscented dish soap, then dried at once with a soft cloth. Sometimes that's all a piece needed.

How the foil bath works

When silver touches aluminum in a warm solution, the two metals form a small electrochemical cell, and the black silver sulphide is turned back into silver. Nothing is rubbed away. That matters, because CCI says "each polishing or chemical tarnish removal takes away a certain amount of underlying silver."

A Johns Hopkins release from 1998 gave a home recipe: wrap the silver in aluminum foil, touching tightly in at least one place, cover it with water containing 4 to 5 tablespoons of baking soda per quart, and simmer gently for 30 minutes. The University of Wisconsin–Madison chemistry department shows the same reaction with foil, salt, baking soda and boiling water, and lists a scalding hazard for its demonstration.

What conservators say it costs

CCI, which describes the method with washing soda, lists the trade-offs plainly:

• The silver that comes back sits on the surface as rough particles, leaving a dull, matte finish.
• Cleaned pieces may tarnish more quickly than polished silver.
• Pitting can occur.
• The piece must be rinsed well to remove every trace of the solution.

Keep these out of the foil bath

• Silver plate and vermeil. CCI warns: "If the object is silver plated, any method of tarnish removal may be very damaging." Vermeil is sterling plated with gold of at least 10 karat, so treat it as gold plate.
• Oxidized silver, the deliberately blackened kind. That black is usually made with liver of sulphur, a sulphur chemical, and the bath turns silver sulphide back into silver. Our own conclusion: it will take the design's dark lines away with the tarnish.
• Anything set with stones, pearls or glued parts. Hot water and soaking can harm many stones and loosen glue. GIA warns that heat and sudden temperature changes "may also fracture some gems."
• Hollow beads, lockets and hollow bangles, and anything with solder joins that could trap liquid.
• Heirlooms and antiques. Ask a jeweler or conservator first.

The water is hot. Use tongs, keep children away, and open a window for the smell.

How do you know a piece is solid? Look at the back. In the United States, "sterling" may be used only for silver that is at least 925 parts per thousand pure. If a piece is plated or unmarked, skip the bath.

About the trick in the video

The video above uses plain foil, shiny side up, with a heaping teaspoon of baking soda per cup of water just off the boil: 5 to 10 minutes for light tarnish, up to 45 for heavy. It sensibly washes pieces first, and keeps pearls, opals, turquoise, coral, amber, glued stones, lacquer and deliberate patina out. The chemistry is sound.

We'd differ, politely, on two points. The video puts plated pieces in the bath, and given CCI's warning, we would not. And it calls this "the preferred method of cleaning for museums," which the sources don't support. The museum conservators we read describe it with cautions, and a 2022 paper in the journal Studies in Conservation notes that this kind of electrochemical treatment "is still disputed among metal conservators." Winterthur's own advice recommends washing, a gentle calcium-carbonate polish and good storage instead.

For a plain sterling chain with heavy tarnish, the bath is reasonable. For a decorated bracelet, an oxidized charm or a Kiddush cup, use a polishing cloth, or nothing.

Only light tarnish? A treated silver polishing cloth is gentler. CCI explains that these cloths carry an abrasive in a low concentration, so they're best for light tarnish.

Volume V, Clean It Right, compares cloths, dips, pastes and the foil bath, and shows how to store silver so it stays bright. For the Kiddush cup, candlesticks and other ritual silver, Volume IV, Jewish Family Secrets, has a full chapter on their care.