Education:  
Cleaning Coins
Last Updated: 05/17/2013
“to clean or not to clean, that is the question”

Coin dealers regularly tell collectors that they should never clean their coins.  In general, this is good advice.  The value of most coins is reduced, often significantly, by cleaning them.  Many coins that would have been worth thousands of dollars have been reduced to a fraction of this value by novice collectors trying to improve the appearance of the item.  At the same time, most dealers will occasionally clean some of their coins.  Obviously there are some acceptable times and ways to clean coins.

“Toning” or light tarnish on silver coins is natural, and many collectors consider this to be highly desirable.  Copper coins start to turn brown when exposed to air for a long period of time, and the natural red colour of copper when newly struck can never be restored by cleaning.  However, there can be times when the tarnish on a silver coin is very unattractive, or carbon marks are expanding and damaging the surface of a coin.  There may also be coins where the surface is physically dirty or covered with contaminants, or the surface may have residue from old PVC holders.  In these cases, some form of cleaning may be beneficial.

For any rare or valuable coin, the best advice is not to do it yourself.  Ask a reputable dealer for advice or assistance first.  For inexpensive or common items, the following suggestions can be used without much risk.  For surface dirt and contaminants, coins may be gently washed with plain water, or soapy water if necessary.  The coins should be patted dry with a towel, and never rubbed.

For silver coins, commercial silver dips can be effectively used to remove tarnish without scratching the surfaces.  Silver dips can be found in many grocery stores or hardware stores, or special silver coin dips can be purchased from some coin dealers.  Silver dips are strong acids, and safety warnings should be followed carefully including ensuring ventilation and using latex gloves if possible.  Silver coins may be dipped in this solution for a few seconds up to a minute if necessary, then rinsed.  The acidic silver dip will continue to react with the coin if it is not rinsed properly and neutralized.  After being dipped, coins should be rinsed extremely well for a couple of minutes under running water.  Any acid residue can be neutralized by then dipping the coin in a solution of water with a small amount of baking soda.  The coin should then be rinsed extremely well again under running water, then patted dry with a very soft towel.  The coin should never be rubbed.  The ideal final rinse is in distilled water.  For uncirculated or near uncirculated coins, this process will often restore a brilliant luster.  In other cases, this process will leave the coins clean, but looking unnatural and sometimes unattractive.  No process will restore a used coin to look like it is new.

Coins which have a slightly green sticky surface have likely been in old plastic holders, and they have been contaminated with a PVC residue.  This residue should be removed as soon as possible to prevent further damage, but doing this without damaging the coins can be a delicate process.  There are a number of commercial products in the market which can remove PVC residue.  One of the best of these is a commercial coin cleaner called “MS-70”.  The product is marketed as a universal coin cleaner, but we do not recommend it for this broad purpose.  In most cases, coins cleaned with MS-70 will lose their natural appearance and will lose much of their value.  However, PVC residue is destructive to coins and it is better to remove this than to leave it as it is.  To remove PVC from coins, a Q-Tip can be dipped into a bottle of MS-70, then gently rubbed over the surfaces of the coin.  The PVC usually comes off quickly and easily.  The coin can then be rinsed under running water and patted dry with a soft towel.

Under the limited circumstances above, cleaning coins may be acceptable and even desirable.  Otherwise, they should be left original as found.  Commercial silver and copper polishes will invariably harm the coins and reduce their value, as will any kind of aggressive rubbing of the surfaces.  For rare or expensive items with PVC contamination or unattractive tarnish or carbon spots, it is best to seek the advice of an experienced professional coin dealer.

Silver dips for coins and “MS-70” coin cleaner are available to order from Canadian Coin & Currency.  Please see the Supplies section.

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