A common question amongst coin collectors, especially younger collectors is how to clean old coins. If you have been given, for example, an old Victorian penny you might be disappointed to see that it's a rather dull dark brown as opposed to a new looking bright shiny copper colour and you could be tempted to want to shine it up so it looks like new in your coin collection.
How to clean old coins if they might be valuable
Well, the simple answer to how to clean old coins is that if the coin is remotely rare or remotely collectable then you shouldn't clean it at all. Coins develop a surface covering called patina which dulls the coin over time though it doesn't necessarily mean that the detail on the coin isn't still well defined or that the coin has become less desirable by collectors. It is caused by exposure to oxygen (or 'oxidation'). Coin collectors expect to see some patina on old coins and it actually adds to the appeal of good quality rare coins. It's quite a subtle thing patination but to the untrained eye or the younger collector, patina is boring and hides the shininess.
Another method used to clean encrusted coins is electrolysis whereby a current is passed over the coin to loosen any debris (and also the patina). If you do a search around you should be able to find ideas about how to do this, or you might be able to find someone local to you who could treat your coin in this manner. The advantage of electrolysis is that it isn't abrasive and it's FAST! There is less likelihood of any accidental damage though damage can still occur because on very old coins, it might be the patina that is holding the coin together! If a collectable rare coin is cleaned using chemicals then it will almost always lose value because collectors won't want a coin that has been artificially brightened up. Therefore the first thing to do before cleaning anything is to check the value of the coin to make sure you're not effectively destroying something of worth. You can do this by looking at the books we mentioned previously or by searching through the for sale listings on the right of this page to see if you can locate your coin.
If you decide that you really do want to clean a coin and you don't care about the fact that it will lose value then there are various acidic chemicals that you can soak it in which should bring it up in a lovely shine. Common chemicals that are good for cleaning coins are:
- Cola (any type)
- Tomato ketchup
- Olive Oil
All will effectively burn off the top layer of patination and leave you with a shiny coin. For younger coin collectors in particular, shiney coins can be a fun way to get them interested, just don't leave them in reach of both your prized collection and a bottle of tomato sauce or you could be in for a shock if they decode to "help" you out one day by carrying out a surprise coin clean!
You should never ever use the above chemicals on a remotely rare coin. If you have what you think might be a rare coin always get advice from a coin dealer before you do anything and never ever be tempted to clean mint, uncirculated coins, or proof coins which are struck with a mirror like finish.
We hope you've found this article useful and that you now know how to clean old coins (and when NOT to clean them!)