Cleaning Dirty or Corroded Coins in a Rock Tumbler
Can I Clean Coins in a Rock Tumbler?
We are frequently asked about cleaning old, dirty or corroded coins in a rock tumbler. The
quick answer to that question is “Yes, coins can be cleaned in a rock tumbler.” but before you
dump your coins into a tumbler barrel you should know two things:
1) Collectors Don't Like Cleaned Coins
If you have coins that are part of a coin collection or have some numismatic value we strongly
discourage you from cleaning them in a rock tumbler. Most coin collectors and dealers will
tell you that you should not clean coins under any circumstances. Cleaning them usually ruins
their value to collectors.
Serious coin collectors expect to see some tarnish on circulated coins. In fact they have a
special name for the tarnish that develops naturally on the surface of circulated coins: “patina.”
If the patina has been removed they usually don’t want that coin in their collection.
If you have any questions about collectible coins in distressed condition it is best to get advice
from a coin dealer or experienced coin collector.
2) A Tumbler Will Damage the Coins
Cleaning coins with a rock tumbler might clean them and give them a brighter appearance but it will
also wear away a small amount of metal from the surface of the coins. When you are finished tumbling
the coins their surface will be covered with minute scratches and some of the details will be worn away.
This type of cleaning will severely damage the coin in the eyes of most collectors. Even if your coin
has no collectible value today it might have collectible value in the future. The damage done by
cleaning is permanent.
Cleaning Coins for Practical Reasons
Many people find coins with a metal detector that have no value in the coin-collecting market. These
coins are often severely tarnished, encrusted and corroded from burial or exposure to the elements for
many years. Other people have coins that were found at a beach and badly corroded by salt water.
Others have coins that were burned in a house fire.
These coins are too dirty to spend and too dirty to exchange at a bank. If they had not been found or
recovered they would be never be used as currency again. If you have a bucket of coins like this you
can clean them up and use them or you can store them in a coffee can until they become part of your estate. :)
Abrasive for Cleaning Coins
We have searched the internet for information about cleaning coins in a rock tumbler. There are lots of
discussions about cleaning coins on metal detecting and beach combing forums. Some people recommend
pea-size gravel, aquarium gravel or sand for use as an abrasive. Others suggest ground walnut shells,
ground corn cobs or sawdust mixed with a polishing compound or extra-fine tumbler grit. Some recommend
using stainless steel shot and pins. These are the same media used by jewelers to clean and polish
jewelry. What you choose as an abrasive depends upon the condition of the coins and how aggressively
you want to clean them.
More Information
Here are a few locations on the web where specific details about cleaning coins with a rock tumbler can be found.
OuterBanksSeaweed shows how he cleans his beach-found coins in a Lortone rock tumbler. Near the end of the video he compares several beach-worn dimes that have probably been in the surf for many years with a dime that has experienced normal circulation. The beach-worn dimes have lost enough of their diameter to be obviously smaller.
219erMan shows how he cleans his metal detecting finds with a small-capacity rock tumbler.
PacificTreasureHunt shows how to clean coins found along Hawaii beaches with a Lot-o-Tumbler vibrating rock tumbler. Many of the coins were encrusted with coral.
