Today’s topic in Numismatic School will be cleaned coins. This topic is quite intense and has many variables the normal collector doesn’t even realize.
In this post I will give a quick over view of cleaned coins. It will take several posts to complete this topic. If you have specific questions on cleaned coins please comment below.
Many people think that cleaning their coins will increase their value. After all, shiny and bright coins are beautiful. When the coin leaves the mint after just being struck, it has a shine or luster. The original “Mint Luster” is gradually destroyed as a coin circulates through commerce. Cleaning a coin will also remove the luster thereby destroying the original surface characteristics. Some of the most common questions asked by new coin collectors are "How do I restore the shine to my coins?" and "How can I clean my coins to make them shiny again?"
The original Mint Luster CANNOT ever be restored.
The technical term that numismatics uses to refer to the shine that new coins have is called mint luster. When the coin dies come into contact with the planchet under extreme pressure during the striking process, this creates the mint luster on the surface of the coin. This process causes changes to the metal of the planchet at the molecular level. The metal of the planchet is forced, by the enormous striking pressure, to flow into the recesses of the coin die and also against the flat surfaces of the dies and against the edges of the collar, which produce the reeded edge, we see on certain coins like dimes or quarters.
The exception to the rule of never cleaning your coins is ancient coins that are at least 1,000 years old. Since banks did not exist back then, people tended to store their coins in inconspicuous places. Most of these places involved being buried in the ground. After hundreds of years of being buried, it is acceptable to remove the dirt by cleaning the coins properly.
If you are not sure of the value of the ancient coin that you have, do not clean it. The science of professionally cleaning coins is referred to as coin conservation. Coin conservation uses special techniques in order to avoid disturbing the metal on the surface of the coin. This usually involves special chemicals that do not damage the metal. Scientists and chemists have perfected this methodology in order to protect the coin from further damage.
