coin guide

How to Clean Silver Coins

The safe way to clean silver coins is a wash, not a polish. The Canadian Conservation Institute's method is lukewarm distilled water with diluted mild soap and no scrubbing, then a distilled-water rinse and air drying. That lifts dirt and leaves the metal alone. Removing tarnish always takes silver with it, and the American Numismatic Association's Reading Room reports that improperly cleaned coins often lose value, sometimes by more than half.

Sort the Coin First: Silver Value or Collector Value

Asked whether collectors should clean their coins, the American Numismatic Association (ANA) answers no. A coin generally loses some value after cleaning, the ANA says, and experienced numismatists spot the work fairly easily. The United States Mint warns that polishing or cleaning coins can reduce their value.

Silver that trades for its metal works the other way. Worn silver coins such as Mercury dimes and silver Washington quarters sell for the metal in them, and washing dirt off removes nothing a buyer pays for. Those are the coins struck before the dime and quarter lost their silver in 1965. Collector Larry House, writing in the ANA's Reading Room in November 2023, put it from the other side: a common coin labeled Details, the grading term for a problem such as cleaning, doesn't offer much unless it's a silver coin with inherent value.

Check the date and mint mark before you call any coin common. PCGS CoinFacts records 264,000 Mercury dimes struck at Denver in 1916, against 22,180,080 at Philadelphia, and the D mint mark is the whole difference. The 1932 Washington quarter works the same way: 436,800 from Denver and 408,000 from San Francisco, against 5,404,000 from Philadelphia. When you can't tell, treat the coin as collectible.

Tarnish is a separate decision. Commercial coin cleaners are chemical dips, and the PCGS glossary describes a dip as a mild acid wash that takes a few layers of metal with every use. A dip is a tool for common silver priced by weight. Collectible, proof and certified coins are no place for one.

Tarnish and Toning Are the Same Film

Tarnish on silver is silver sulfide (Ag2S). It forms when silver reacts with sulfur-containing gases in the air, most commonly hydrogen sulfide (H2S). Toning, the color collectors pay for, is the same compound. On a coin, the Canadian Conservation Institute describes toning as silver sulfide whose color depends on the thickness of the film.

As the film grows from 10 to 100 nanometers thick, its color changes from yellow through red-brown to blue, and above about 100 nanometers it's black, the true color of silver sulfide. A golden Morgan dollar, a blue one and a black one differ only in how thick that layer has grown.

That's why collectible coins should never be cleaned. You can't remove the tarnish and keep the toning. Every coin begins to tone as it leaves the die, PCGS notes. Many numismatists prize toning and tarnish, the Canadian Conservation Institute reports, and they value toned silver coins in particular. Strip the film and you've removed what a collector grades.

Why 90% Silver Darkens Faster Than .999 Bullion

Copper is the reason old coins darken faster than modern bullion. On silver-copper alloys the tarnish also contains copper sulfide (Cu2S), and the tarnishing rate rises with copper content because copper is the more reactive metal. The United States Mint struck its silver coins at .900 fineness from 1837. So junk silver, the trade's name for 90% silver coins with no collector premium, is 10% copper, while a .999 fine American Silver Eagle has almost none. A 1964 Washington quarter that has gone dark beside a bright Silver Eagle in the same box is behaving normally.

How to Wash a Silver Coin Without Rubbing It

Washing takes off what handling puts on. It removes surface dirt and contaminants such as oils, salts and acids, the Canadian Conservation Institute says, and it doesn't affect any underlying patina. The institute's procedure, published as CCI Notes 9/4, has five steps:

1. Work in a well-ventilated space.
2. Wash the coin in lukewarm distilled water with diluted mild soap. Don't scrub, and never use powdered dishwasher detergent.
3. Rinse it in distilled water.
4. Soak it in pure acetone, which degreases the coin and drives off the water. Acetone is flammable, so keep it away from heat and flame.
5. Let the coin air dry on a paper towel.

Both the Mint and the ANA describe the same wash with less equipment. The Mint uses mild soap and water and pats the coin dry with a soft towel, because brushing or rubbing can scratch. The ANA names mild dish soap and distilled water, then air drying or a gentle pat, and only for a coin too corroded to recognize. Nothing rubs the coin in any of the three. A Mercury dime still dark after washing has tarnish, not dirt.

Why Every Tarnish Remover Takes Silver With It

No tarnish remover is gentle. Tarnish is the coin's own silver, and each cycle of tarnishing and cleaning loses some of it.

Polishes, Pastes and Cloths

Silver polishes are abrasive, CCI Notes 9/7 warns: they remove silver along with the tarnish and leave a pattern of fine scratches. Graders call those scratches hairlines, the fine lines cleaning leaves. The WIPED label at NGC covers hairlines in an isolated area, usually from accidental mishandling, and it still requires a Details grade. A single wipe across a Peace dollar with a shirt counts.

Chemical Dips

The same Canadian Conservation Institute note explains the chemistry: a dip is an acid plus a complexing agent, and it dissolves tarnish at a faster rate than the silver underneath. Keep exposure short, the note adds, to avoid pitting. A dipped Morgan dollar looks new because no tarnish remains in the recesses of the design.

Authorities don't agree on dips. Dipping isn't cleaning by the PCGS definition unless it's been done repeatedly or improperly. The Canadian Conservation Institute says not to use coin dips on coins at all, because acid left on the surface through insufficient rinsing can lead to degradation. Either way, every dip takes metal, and leftover acid keeps working.

Aluminum Foil and Soda

The foil trick is real chemistry, and that's the problem. In CCI Notes 9/7, silver touches aluminum in a warm solution of washing soda (sodium carbonate), and the tarnish slowly disappears through an electrochemical process. That description is for silver objects, not coins, and it uses washing soda, not the baking soda in home recipes.

Tarnish doesn't leave the coin this way. The reaction turns it back into silver that stays on the surface as rough particles, and the finish goes dull and matte. Silver cleaned this way may tarnish again faster than polished silver, the Canadian Conservation Institute adds, and it can pit.

What a Grading Service Does With a Cleaned Coin

A cleaned coin, by the PCGS definition, is one whose original surface is gone, and neither PCGS nor NGC will put a number on one. NGC says improperly cleaned coins can't receive a numeric grade from 1 to 70 and gives them a Details grade instead. PCGS returns them with a No Grade code, and code 92 means cleaning. On PCGS and NGC graded coins, that note takes the grade's place on the label.

Cleaning damage doesn't reverse. Improper cleaning permanently impairs a coin's surfaces, NGC says, and its conservation service can't fix the fine scratches that amateur cleaning leaves. The ANA's phrase for the result on a circulated coin is "bright but worn," and a December 2023 Reading Room article by Kevin Wang traces the unnatural shine to disrupted flow lines, the source of mint luster.

Films and Spots That Aren't Tarnish

PVC Residue on 90% Silver

A green or sticky film isn't tarnish. The plasticizer in vinyl (PVC) flips produces a green corrosion product on copper-alloy coins, the Canadian Conservation Institute warns, and silver coins with a high copper content may show it too. The PCGS glossary describes the film as usually green, and clear and sticky in its early stage. NGC warns that PVC residue will eventually cause permanent damage if it isn't safely removed. Move the coin to an inert plastic holder, and treat the residue as a job for the acetone soak or for NGC Conservation.

Milk Spots on Modern Bullion

Milk spots, the white spots that appear on modern silver bullion coins such as the Silver Maple Leaf, aren't dirt and don't wash off. They're a form of corrosion caused by the mint's manufacturing process, NGC says, and they can develop anytime from right after striking to many years later. NGC's own conservators can't remove them. Prevention happens at the mint: the Royal Canadian Mint applies its MINTSHIELD surface protection to Silver Maple Leaf coins dated 2018 and later. A milk spot doesn't change the silver content. Rubbing one only adds hairlines.

Storage That Keeps Silver From Needing a Cleaning

Tarnish needs sulfur, and not much of it. In a Canadian Conservation Institute demonstration, a freshly boiled egg sealed in a box with polished silver turns the silver yellow within 5 to 30 minutes. Handle silver in cotton gloves, never latex: CCI Notes 9/4 warns that the sulfur in latex causes silver to tarnish. Hold a coin by its edges, because the Mint's care page says the natural oils on skin can be corrosive.

Keep relative humidity as low as possible, ideally below 30%. Choose coin holders made from an inert plastic: CCI Notes 9/4 lists polyethylene, polypropylene, polyester film, polystyrene and acrylic, and says to avoid vinyl. For storage, CCI Notes 9/7 says to seal each piece of silver in its own polyethylene bag, and that tarnish needn't come off first.

Toned and Spotted Silver in Our Catalog

Random-year American Silver Eagles and dimes and quarters dated 1964 or earlier in our catalog can arrive with toning or minor marks, and neither changes the metal content. We verify every item with modern testing equipment and numismatic expertise.

Frequently Asked Questions

How to clean fingerprints off silver coins?

Fresh fingerprints are skin oil. The Canadian Conservation Institute wash lifts oil before it marks the metal: distilled water with mild soap, a distilled-water rinse, then a soak in pure acetone to degrease the coin. The Mint says fingerprints leave marks that are hard to remove, and we haven't found a mint, grading service or conservation body that says a set print comes off.

What is a good liquid for cleaning coins?

Distilled water with a small amount of mild soap. The Canadian Conservation Institute follows the rinse with a soak in acetone to degrease the coin and remove water. Neither liquid removes tarnish. The liquids that do are acid dips, which work by dissolving metal, and most metal cleaners contain abrasives that scratch a coin's surface.

What is the best way to clean silver bars?

Most of the time, by not cleaning them. Silver bars sell by weight and purity, so a tarnished 10 oz bar holds the same silver as a bright one. CCI Notes 9/7 says tarnish needn't come off before storage, and that it's better to remove it only when necessary. For dirt or grease, the same distilled-water wash is enough.