How to Clean Tarnished Silver: The Foil and Washing Soda Method, and What Never Goes in the Bath

Tarnish is not dirt sitting on your silver. It is your silver, chemically bound to sulfur. That is why a polishing cloth that removes tarnish also removes a little silver every time, and why the old foil-in-hot-water trick feels like magic: it hands the sulfur to the aluminum and leaves the silver behind, on the spoon, where it started.

This guide explains what tarnish is, how the foil bath works, why conservators specify washing soda rather than the baking soda most recipes call for, the exact method, and the pieces that must never go in the bath. We sell the electrolyte at the center of it, Soda Ash Technical Grade, which is sodium carbonate, so we have also been careful to say where the bath is the wrong tool.

Last reviewed 12 November 2026 against the sources cited below. This is a practical cleaning and chemistry guide, not medical, legal or regulatory advice, and it is not conservation advice for valuable antiques. If washing soda gets in an eye, flush with water for at least 15 minutes; for poisoning questions call Poison Help at 1-800-222-1222. How we researched it is set out at the end.

What is silver tarnish, and why does silver turn black?

Silver tarnish is a thin film of silver sulfide (Ag₂S) that forms when silver reacts with sulfur gases in the air, mainly hydrogen sulfide and carbonyl sulfide. The Canadian Conservation Institute (CCI) notes that on sterling silver the film also contains copper sulfide, because sterling is 92.5% silver and 7.5% copper, and “copper is more reactive than silver.”

The color tells you how thick the film is. A 2022 paper in Studies in Conservation describes tarnish layers running from yellowish-brown to blue-black as they thicken, which is why a lightly tarnished spoon looks golden and iridescent and a neglected one looks black.

The sulfur comes from more places than most people expect. CCI’s list of tarnishing sources includes eggs and other foods, wool, vulcanized rubber (rubber gloves, stoppers, pencil erasers), certain paints, protein-based glues, some modelling clays, cement and grout. Silversmith Jeffrey Herman adds mayonnaise, onions, mustard, garlic and fish to the food list, and warns that rubber bands and newspaper can cause “deep discoloration.”

Two things speed it up. Humidity: “For a given concentration of hydrogen sulfide, silver tarnishes faster as the RH climbs,” CCI writes. And direct contact with a strong source: CCI reports that silver next to a freshly hard-boiled egg starts to yellow within minutes, while a dark layer in a museum case may take months or years.

The takeaway: tarnish is silver that has become silver sulfide. Any method that rubs it off takes that silver with it. The foil bath is the one household method that turns it back into metal.

How does the aluminum foil method clean silver?

The foil method works by electrochemistry: aluminum touching the silver in a warm electrolyte corrodes in place of the silver, and the reaction reduces silver sulfide back to silver metal. CCI describes it this way: “The process is electrochemical, with the carbonate solution acting as the electrolyte. As long as contact is maintained between the two metals, the aluminum corrodes and hydrogen gas is produced. This gas then reacts with the tarnish, reducing it back to silver metal.”

The textbook summary of the overall reaction, as taught in chemistry classroom demonstrations, is:

3 Ag₂S + 2 Al → 6 Ag + Al₂S₃

Aluminum gives up electrons (Al → Al³⁺ + 3e⁻) and the silver in the tarnish takes them back (Ag⁺ + e⁻ → Ag). Conservation scientists write the silver side as Ag₂S + 2H₂O + 2e⁻ → 2Ag + H₂S + 2OH⁻, which also explains the smell: the sulfur leaves as hydrogen sulfide, the rotten-egg gas. Open a window.

Johns Hopkins materials scientist and corrosion expert Jerome Kruger put it plainly in a 1998 university release: “There is a flow of electrons between the silver object and the aluminum foil, and that’s what removes the tarnish.” Because it is a circuit, the silver has to touch the foil, or touch another piece of silver that is touching the foil.

The big difference from polish is where the silver ends up. The US National Bureau of Standards wrote in 1958 that the electrolytic method removes tarnish “with practically no loss of silver.” Polishes, by CCI’s account, “remove silver and tarnish from the surface of an object” and “leave behind a pattern of fine scratches.” A 1918 New-York Tribune household column went further, claiming that even careful polishing with whiting loses twenty-five times as much silver by weight as the electrolytic method.

There are trade-offs, and conservators are clear about them. CCI notes that the reduced silver stays on the surface “in the form of rough particles that leave a dull, matte finish,” which a gentle pass with a silver polishing cloth brings back to a shine, and that “Objects cleaned by this method may tarnish more quickly than silver that has been polished.”

Baking soda or washing soda: which is better for cleaning silver?

Washing soda (sodium carbonate) is the electrolyte the Canadian Conservation Institute specifies for this method, and it is the one older household guides preferred, even though most recipes online now call for baking soda. CCI’s note on silver care describes the bath as “a warm solution of sodium carbonate (washing soda)” and does not mention baking soda at all.

The preference is not new. The 1918 New-York Tribune column that taught readers the method said there was “little choice between the two,” then added: “The washing soda is cheaper and somewhat quicker in its action; therefore, if convenient, it is the better ingredient.” When S.C. Johnson patented a consumer silver cleaner in 1982, built around “an aluminum foil pouch,” the electrolyte it specified was sodium carbonate at 1.4 to 5% by weight.

Our explanation for why washing soda behaves better is about the foil, not the silver. Aluminum protects itself with an invisible oxide skin, and Products Finishing notes that “A protective oxide film of aluminum is only stable in a pH range of 4.5 to 8.5.” Baking soda solution, at pH 8.3, sits inside that window; washing soda, at pH 11.5, sits well outside it, so the aluminum stays bare and active. That is our reading of the chemistry, consistent with the sources, not a finding any of them states.

To be straight about the evidence: we found no controlled, published side-by-side test of the two sodas in a foil bath. What we found is a conservation institute that names washing soda, a 1918 guide that preferred it, a 1982 patent built on it, and a pH difference that explains it. Baking soda still works, which is why the US Bureau of Standards recipe of 1958 used it.

How do you clean tarnished silver with foil and washing soda?

You clean tarnished silver with foil and washing soda by laying the silver on aluminum foil in a hot sodium carbonate solution until the tarnish clears, then rinsing and buffing it. First check the list in the next section: if a piece is plated, hollow, patinated or set with stones, keep it out.

What should never go in a silver cleaning bath?

Silver plate with worn spots, hollow-handled knives, sealed hollow pieces, deliberately darkened or nielloed decoration, and anything set with pearls, stones, wood, bone or ivory should stay out of a foil bath. Each has a specific reason.

Quotations from the sources listed at the end. GIA’s advice is general jewelry care, not specific to foil baths.

If you are not sure whether a piece is sterling or plate, look for a “925” or “sterling” mark, and assume anything unmarked is plate. Our guide to testing gold and silver with nitric acid explains how jewelers check, and why that test leaves a mark.

Is it better to polish silver, use a silver dip, or use the foil bath?

The foil bath removes tarnish with the least loss of silver, polish gives the brightest finish, and dips are fastest but carry the most hazardous chemistry. Most collectors end up combining them: bath for heavy tarnish, a cloth or mild polish for the final shine.

The dips deserve a closer look because they are sold as the easy option. NBS described them in 1958 as “an acid, aqueous solution of thiourea plus a wetting agent.” Current safety data sheets for three retail dips we read list thiourea at roughly 5 to 10%, an acid (sulfuric, phosphoric or citric), and the hazard statement H351, “Suspected of causing cancer.” If you use one, follow its label exactly, apply it with a swab rather than immersing (CCI’s advice) and rinse quickly.

Does toothpaste clean silver?

Toothpaste does remove tarnish, but it does it by abrasion, which means it also removes silver and can scratch. Silver restorer Jeffrey Herman is blunt: “Toothpaste should NEVER be used as a silver polish,” because some formulas contain ingredients that are much too abrasive. CCI goes further than toothpaste, warning against general multi-purpose metal polishes on silver because they are more abrasive than silver polishes. Google’s own AI answer for this query still lists toothpaste as a method. We would not.

If you want to polish by hand, the conservation choice is a very fine, soft abrasive. A 1990 study in the Journal of the American Institute for Conservation found that calcium carbonate, gamma alumina and chromium oxide in deionized water with a nonionic surfactant “removed tarnish successfully and caused the least amount of damage to the silver.”

How do you keep silver from tarnishing?

You keep silver from tarnishing by keeping sulfur away from it and keeping it dry. The steps conservators recommend are simple:

• Wash after use. AIC advises washing tableware after serving with soapy water and drying it thoroughly with a clean cotton towel. Egg, mayonnaise and mustard are the worst offenders.
• Wrap and bag it. CCI recommends acid-free, “unbuffered” tissue inside a sealed polyethylene bag, with silica gel and activated charcoal if you can. AIC says never to store metal in PVC bags or sleeves.
• Use silver cloth. CCI says tarnish-inhibiting cloths embedded with tiny silver particles are “particularly effective,” because the gas reacts with the cloth first.
• Keep it dry. CCI advises storage below 50% relative humidity.
• Keep sulfur sources away. No rubber bands, newspaper, wool felt or ordinary cardboard boxes. Herman warns that non-archival corrugated cardboard “may contain acids and sulfur.”
• Skip the dishwasher for good silver. Herman says heat and harsh detergents “will eventually whiten the silver.”

Is washing soda safe to handle?

Washing soda is a strong household alkali that is easy to handle with basic precautions; its main hazard is to the eyes. The NIST safety data sheet for sodium carbonate classifies it as an eye irritant (Category 2A, H319, “Causes serious eye irritation”) and does not classify it as a skin irritant, but notes that concentrated solutions may cause irritation, blistering or burns, and that repeated exposure can cause dermatitis.

• Wear eye protection and chemical-resistant gloves when you mix the bath.
• If it gets in your eyes, flush with water for at least 15 minutes. NIST notes that prompt flushing makes permanent damage unlikely.
• Keep it away from acids: the safety data sheet lists acids as incompatible materials. Do not add vinegar or lemon juice to the bath.
• Store it dry, sealed and labeled, away from children, food and pets.

Soda Ash Technical Grade is sold for cleaning and industrial use, not as a food ingredient, which is one more reason to rinse well and wash flatware in soapy water after the bath. Read the soda ash safety data sheet before you use it.

Is soda ash the same as washing soda?

Yes, chemically. Soda ash is anhydrous sodium carbonate (Na₂CO₃, CAS 497-19-8), the same compound sold in the laundry aisle as washing soda. The older name “sal soda” refers to the crystalline decahydrate (Na₂CO₃·10H₂O), which is mostly water by weight: if that is what you have, use about 2.7 times as much to reach the same strength.

Our Soda Ash Technical Grade is a white crystalline powder sold from a 2 lb pack up to pallet quantities. It is the same chemical people use to raise pool pH, build laundry detergent and clean winemaking equipment, which our complete guide to soda ash and winemaker’s guide to cleaning with soda ash cover in depth. At the strength above, a 2 lb pack makes about 15 two-liter baths.