How to clean silver coins (and any coin) without damaging them

Step by step: how to clean silver coins

Safety first. Conservators sometimes finish with an acetone soak to remove oils; acetone is highly flammable, so use it only in a ventilated room, away from flames, in a small covered glass dish, and never on coins with lacquer or paint. Keep coins and cleaning solutions away from small children, who can swallow coins.

1. 1

   Decide whether the coin should be cleaned at all

   If the coin is old, rare, graded, proof or might be worth more than face value, do not clean it; ask a coin dealer or a grading service first. Dark toning on silver is valued by many collectors. Washing is for common coins with surface dirt, or coins you only want to look at.

2. 2

   Handle it by the edges, with gloves

   Hold coins only by the rim, never the faces. Skin oils and acids can leave fingerprints that etch in over time. Wear cotton gloves for silver, since the sulfur in latex can tarnish it.

3. 3

   Make a gentle wash

   Fill a small bowl with lukewarm distilled water and add a single drop of mild liquid soap. Do not use dishwasher detergent, which is far too harsh. Tap water can leave mineral spots, so use distilled for both bowls.

4. 4

   Soak and swish, do not scrub

   Lay the coin in the bowl for a few minutes and swish it gently. For caked-on dirt on a common coin, let it soak longer, changing the water when it clouds. Do not rub the faces with a cloth, brush or fingers, which leaves fine scratches collectors can see.

5. 5

   Rinse in clean distilled water

   Move the coin to the second bowl of distilled water and swish it to remove all soap. Lift it out by the edges.

6. 6

   Air dry on a soft towel

   Lay the coin on a folded paper towel and let it air dry, turning it once by the edges. Pat only the rim if you need to. Do not wipe the faces dry.

7. 7

   Store it in a PVC-free holder

   Put the dry coin in an archival flip or capsule made of Mylar, polyethylene or polystyrene. Avoid soft vinyl flips, which contain PVC. Store the collection somewhere cool and dry.

Does cleaning coins lower their value?

Yes, often a lot. NGC, a major grading service, says unskilled and improper cleaning is among the most common reasons a coin gets a Details grade instead of a numeric grade, and that harsh cleaning cannot be corrected by conservation. Light, non-destructive cleaning on older coins may still allow a numeric grade.

The Canadian Conservation Institute’s note on coins says many numismatists believe coins should never be cleaned, and that toned or tarnished silver coins are particularly valued. It advises leaving corrosion removal to a conservator, but says coins can be washed to remove surface dirt, oils, salts and acids from handling, and that washing does not affect the underlying patina. It also says coin dips and metal cleaners should not be used on coins: dips contain acids that can cause damage if not fully rinsed, and most metal cleaners contain abrasives that scratch.

How to clean coins by type

Treat a coin according to what it is worth to a collector, not by how dirty it looks.

You will see tarnish removal by aluminum foil and a warm soda solution recommended for silver. The CCI note on silver describes this electrochemical method for silver objects, but also says every tarnish removal takes some silver with it. On a coin it strips the toning collectors value, so keep it for silverware. Our silverware guide explains it.

How do you keep coins from tarnishing?

Store them dry, sealed and away from PVC. Prevention protects value better than any cleaning.

• Use holders made of inert plastics such as polyethylene, polypropylene, Mylar or polystyrene. The CCI warns that the plasticizer in PVC vinyl flips corrodes copper alloy coins, producing a green residue, and that silver coins with high copper content can be affected too.
• NGC’s conservation service notes that PVC from soft flips and some mint packaging slowly leaches onto coins and will eventually cause permanent damage if not professionally removed.
• Keep humidity low; the CCI notes metals corrode faster as humidity rises, and silica gel helps in a closed box.
• Avoid wooden cabinets and drawers, especially new oak, which give off acidic vapors.

Mistakes to avoid

• Polishing a silver coin bright with silver polish or a polishing cloth.
• Dipping coins in silver dip or vinegar and not rinsing it all off.
• Scrubbing with baking soda or a toothbrush, which leaves hairline scratches.
• Holding coins by their faces and leaving fingerprints that etch in.
• Storing coins in old soft vinyl flips that contain PVC.
• Cleaning a coin before finding out what it is worth.