Apr 2024


Apr 2024

Why Do Silver Coins Tarnish and How to Clean Them

By StoneX Bullion

Even the highest purity silver coins will eventually lose their gleam and begin to tarnish over time. In this article, we look at what tarnish is and why silver coins tarnish. We also offer a few different methods for cleaning tarnished silver coins and tips to prevent silver coins from tarnishing.

Before we begin, we want to make one thing clear: generally, in the world of silver coin collecting, cleaning coins is never advised. No matter how gently you do it, cleaning silver coins can damage the surface of the precious metals and diminish their value.

Some estimates say that cleaning silver coins can decrease their value by 20-30% less than the spot price. When it comes to numismatic value, cleaning silver coins can decrease their collectible value by more than half. Of course, you will always be able to sell your silver coins for their precious metal content, however you may lose access to the lucrative numismatic market.

So - proceed with caution! Let’s begin.

What is tarnish?

Tarnish, also known as toning, is a thin layer of natural discoloration and corrosion that appears on the surface of silver (and other metal) items over time. Tarnish is different to rust and only affects the top few layers of the silver object. While it can change the appearance of silver items, tarnish also acts as a protective layer that prevents corrosion and damage to the underlying metal.

Generally, the less pure the silver alloy, the more susceptible it will be to tarnish over time. Because pure silver of 999 fineness doesn’t tarnish easily, most investment-grade silver bullion coins and bars can be safe from tarnish if stored correctly. That said, they can still be prone to discoloration over time.

Read: The Fineness & Purity of Silver Explained

Silver items can tarnish suddenly, and some items can tarnish silver immediately upon contact. These include perfumes, perspiration, salt, fruit juices, vinegar, and onions, which all contain sulfur.

If left alone and not removed, tarnish will form dark areas in small creases on a coin’s surface. This is known as ‘patina’ in the numismatic world and can actually be sought-after when it comes to collecting historic coins and antiques. Unlike new or cleaned silver, which is bright and reflective, old silver with a patina has a warm finish.

Different colors of silver tarnish or toning

Tarnish can appear on silver in various colors, including:

  • Black: Black tarnish is caused by sulfides and is often seen on ancient coins that were buried in organic matter in the earth.
  • Green: Green tarnish appears in silver coins alloyed with copper. The color comes from copper carbonate or copper chloride.
  • Yellow: Yellow is an early sign of a silver coin beginning to tarnish.
  • Rainbow: From the initial yellow color, tarnish can turn magenta, cyan, and black, just like an oil slick. The rainbow color appears as a result of different wavelengths of light refracting through the film.

Why does silver tarnish?

Silver coins tarnish as a result of a chemical reaction that occurs when silver is exposed to moisture and air pollutants. This is mostly a reaction of silver atoms with sulfur compounds that forms a film of silver sulfide on the coin’s surface.

Things like high humidity, air pollution, and exposure to different chemicals can make a coin tarnish faster. Many coin collectors prefer to seek tarnished silver coins because they carry much more history in their appearance.

Tarnish vs rust: What is the difference?

Tarnish is different to rust. While both are technically forms of corrosion, their composition, causes, and effect on the metal are different. Tarnish happens when silver (or another metal) reacts with other elements in the environment to form a thin layer of discoloration on an object’s surface. It is purely superficial and doesn’t lead to structural damage.

Rust, on the other hand, is the corrosion of iron and its alloys. When rust appears, it begins to eat into the metal and will eventually cause structural damage.

How to clean tarnished silver coins safely

Before we get into the topic of cleaning silver coins, it’s important to reiterate how controversial it is in the world of numismatics. An avid coin collector will genuinely prefer and favor silver coins that have developed a patina. In some cases, patina might even lead to a more valuable coin.

If you own tarnished silver coins, our advice is to leave them as they are and avoid cleaning or altering them in any way. Improper cleaning or the use of abrasive materials might irreparably damage your silver coin and diminish its value.

Continue reading: What are the Best Silver Coins to Buy?

That said, if you wish to go ahead and clean silver coins safely, we’ll explore a few different methods below.

1. Baking soda

While it’s not recommended to use abrasive cleaners on silver coins, baking soda is one of the most efficient ways to remove tarnish from silver items. To use baking soda as a silver tarnish remover, mix a small amount of the powder with enough water to create a stiff paste that you can then rub onto the surface of your silver coin. The baking soda will remove dirt and tarnish in a coin’s crevices. After rubbing on the baking soda, rinse the clean coins with lukewarm water and dry.

Another way to clean silver coins with baking soda is to create a dip. For this method, you want to line a bowl with aluminum foil, shiny side up. Pour in boiling water and baking soda. Once the baking soda has dissolved, add your silver coins into the bowl. You’ll see a chemical reaction take place which attracts the tarnish to the foil. Don’t leave the coins in for too long - ten seconds is likely to be enough. Remove the coins with a pair of tongs and let them cool before rinsing with warm water and drying thoroughly. If there is still tarnish, you may repeat the process again.

2. Toothpaste

Toothpaste can also help remove tarnish from silver items. This method is slightly less abrasive than baking soda but can also be a little costlier. The bonus is that you don’t need to create your own paste and can simply squeeze the toothpaste out from the tube, rub it onto your silver coin until the tarnish is removed, then rinse and dry.

3. Lemon juice

Most of us have easy access to lemon juice at home, making this method one of the easiest. Unlike toothpaste and baking soda, lemon juice isn’t physically abrasive but can remove tarnish due to its acidic nature which will eat away at dirt and toning.

The way that lemon juice works is that it essentially eats away a thin, superficial layer from the top of the coin. This isn’t particularly recommended for valuable silver coins or collectible items - but then again, none of these cleaning methods are really advised for these kinds of items.

When using lemon juice to remove tarnish, you can create a type of ‘bath’ by pouring the juice into a small dish or bowl. Let your silver coins sit for a few minutes in the bath before rinsing with lukewarm water. If there’s still some tarnish, you can pop the coin in for another lemon juice bath before rinsing again.

4. White vinegar

Here’s another household item that can be used to clean silver coins. White vinegar works similarly to lemon juice and has an acidic nature that can help remove tarnish or toning. Again, you’ll want to pour the white vinegar into a bowl or dish to create a ‘bath’ for your silver coins. Leave these to soak for a while before rinsing under warm water and drying carefully.

To make your bath even stronger, add a little bit of baking soda - though be warned, the combination can froth up and fizz (which is kind of fun in itself). Again, be aware that white vinegar can eat away at the top layer of metal on your silver coins. If you want to maintain its numismatic value and resell the coin at some point, you may be better off leaving it alone.

See: How to Tell the Difference Between Real & Fake Silver

5. Silver dip

Silver dip is a less abrasive method of cleaning silver coins. In the world of numismatics, some people look upon cleaning with silver dip a bit more favorably, while others still firmly abhor the use of any type of cleaning agent - silver dip included! Purists will always prefer an unaltered coin in its natural (if somewhat tarnished) state, and some claim that silver dip can still be abrasive and not only damage a coin, but give it an inauthentic bright appearance that ruins its collectible value.

Silver dip, for those who aren't in the know, is a specialized cleaning solution that removes tarnish from silver items. It's usually made from thiourea or potassium thiocyanate mixed with solvents and surfactants. If you choose to go the silver dip route, be sure to follow the instructions on the packaging to avoid damaging your coins.

Tips for cleaning silver coins

We’ve outlined above a few popular - though controversial - methods for cleaning silver coins. To help answer any other lingering questions you may have, we’ve also compiled a few tips for cleaning silver coins:

  • Never use a dishwasher to clean your silver coins (or other silver items). Temperatures are too high and many dishwasher soaps use abrasive chemicals that can damage your coins.
  • Silver coins that are only slightly tarnished may be washed with warm water and phosphate-free soap then dried carefully.
  • Never use abrasive scourers or steel wool to clean your coins.
  • If you really want to prevent tarnish on your silver coins, consider polishing them with a gentle silver polish and soft cloth. When polishing, use straight strokes not circular motions. After polishing, use a clean cloth to remove the polish then wash with warm water and dry carefully.
  • Don’t have any of the aforementioned household cleaning agents on hand? Try soaking your silver coins in Coca-Cola or lemon soda for a few minutes.

Tips to keep your silver from tarnishing

If you really don’t like the idea of tarnished silver, we’ve got some tips to prevent tarnish from forming in the first place.

  • Store your coins safely: Proper storage can help prevent tarnishing. Keep your silver coins in a cool, dry place away from direct sunlight, moisture, and chemicals.
  • Keep in airtight containers: When storing your silver, keep them in an airtight container to further protect them from the elements and slow down the tarnishing process.
  • Use silica gel: Silica gel packets, which you often find in shoeboxes or handbags, can absorb moisture in the air and help prevent tarnishing. Consider keeping a gel packet near your silver coins.
  • Wear gloves: Wear cotton gloves when handling your silver coins to minimize the transfer of oils from your skin.

Summary: Cleaning tarnished silver coins

Now you know how to clean tarnished silver coins, you have all the information you need to make your decision. Again, we’ll reiterate that cleaning collectible silver coins isn’t advised as they may lose their numismatic value. Using the wrong substances, or cleaning incorrectly, can also damage the surface of your coin.

Ultimately, tarnish will not significantly affect the value of your silver coins. If anything, it can enhance the aesthetic appeal and value of your collectible pieces. Even if heavily tarnished, the amount of silver in your coins will remain the same and their value will be retained. So is it really necessary to clean them? The choice is up to you.

Looking to invest in silver? StoneX Bullion is your reliable partner for silver bullion bars and collectible coins, as well as gold, platinum, and palladium. Browse our extensive range of precious metals bullion from the world’s most well-known mints and start investing today.