Tips on cleaning coins
I found this old coin, but it's so covered with dirt I cant tell what it is. What's the best way to clean it?
- Sometimes, the answer is "don't!". Some coins will actually loose value if polished to a shine. The goal of cleaning is to remove dirt, not the coin itself and choosing the cleaning method which causes the least amount of damage to the coin is critical!
Methods of coin cleaning
Mild Soap and Water - Try the safest method first, simple soap and water and a soft cloth or soft toothbrush. Avoid all wire brushes as they will scratch! Try to avoid "spit cleaning" in the field as this may make the existing dirt scratch the coin. If you must check for a date, carry some water to wash the coin with and use a soft towel.
Need something a little stronger? Try vinegar, cola, or even ketchup. They are mildly acidic and can be good cleaning agents. Don't immerse a coin in these products too long as they could dissolve entirely! About 10 minutes, then check it. If your not sure, test on a "practice" coin.
Electrolysis – Using a class 2 transformer (9 to 12vdc, 300mA typically) in a solution of baking soda (1 tbl. spoon) and water, you can "bubble" away deposits of dirt. You will also need a "sacrificial" Stainless Steel washer or bolt as an electrode. Check periodically so as not to "over-do-it". Make sure the bubbles come FROM your coin, not the SS washer or what you have there is plating!
Rock Tumblers – A small tumbler costs about $30. Use mild detergent and small plastic beads or items smooth and softer than the coin. Check the tumbling periodically so as not to "over-do-it".
Helpful hints:
- don't mix coin types, tumble copper with only copper, silver with only silver.
- fish tank gravel (the smooth type) with dish soap works well for coins fresh out of the ground, but check periodically.
Silver Plates – There are companies that make a silver cleaning plate. For Silver cleaning only. Do not mix silver with copper coins.
Ultrasonic Cleaners – Readily available and relatively cheap, these work pretty good.
Civil war cannon ball, old firearm - Don't try to "get all that rust off" because if you do, what will be left is "nothing". Try soaking in a light veggie oil, like olive oil or linseed oil (very expensive). No, you can't use car motor oil. The goal here is to preserve what you have and prevent any further rust or corrosion. Seal it in plastic block? Well, while that may preserve it forever, it might become valueless to collectors as most would want to actually touch, feel and handle the antique item as it was "back then".
What’s my treasure worth?
Here are some links to websites that are handy for looking up coin values:
www.coinflation.com
www.cointrackers.com
Recommended reading:
Also if you don't already own one, we recommend purchasing the booklet, "The Sport of Coin Hunting with a metal detector", by Charles Garrett. It's all about Coins, how to recover them properly, and there is also a section about cleaning coins.