How to clean a bronze coin
Reverse of 1844 Crown with attractive toning
How to Clean Coins
The best advice we can give for most people about cleaning coins is.
We see far more coins ruined by cleaning than we see coins which have been improved by cleaning.
Generally speaking coins can not be improved by cleaning them. It is certainly impossible to improve their condition by doing so.
We first saw this advice in 1962 edition of Seaby's Standard Catalogue, and it still appears in the same book today, although it is now published by Spink.
If You Have To Ask - Definitely Do Not Clean Them!
It's true that if you had to ask about cleaning your coins, how to, or whether to, then the best thing for you to do is nothing. Don't clean them. You will almost certainly not improve them, and you are much more likely to spoil them.
We Occasionally Clean Coins
Never say never!
We occasionally clean coins, but then we have been in the business for over 36 years, so we know which ones might benefit from careful cleaning, and which will not.
We also know how to clean coins, and more importantly, how not to clean coins.
Even though we never clean coins unnecessarily, we occasionally get it wrong, and end up with a worse-looking coin after we have cleaned it.
If You Really Must - How To Clean Coins
First - Cleaning Gold Coins.
Because gold is a noble metal, it is unlikely to become discoloured. Wash carefully in warm, even boiling, soapy water (detergent is also OK). You may even brush it gently with a soft brush. Be careful, if there is any grit present it will make minute scratches on the surface.
Cleaning Silver Coins.
Silver acquires a tone through tarnishing. A pleasant, even tone can enhance the appearance and desirability of an old silver coin. Some toning has rich blue, green, indigo, and violet "oil effects", toning like this will be appreciated by most connoisseurs. Do not clean any silver coin with this type of toning.
If a silver coin is so dark brown or black that its design can hardly be seen, then it may. be worth dipping, usually in a proprietary solution, such as Goddard's Silver Dip. If in any doubt, don't!
Whatever you do, do not use any abrasive paste or cloth.
Warm soapy water may also be used.
Even if silver coins are carefully cleaned, they end up looking artificially bright and silvery. Many collectors
will not buy a silver coins which looks as though it has been cleaned.
Cleaning Copper and Bronze Coins
Copper and bronze coins usually look awful when they have been cleaned. They are more easily ruined than silver or gold coins. Once again, the best advice is do not clean copper or bronze coins.
Leave It To The Experts
Usually, the people who ask about cleaning coins are those who have recently acquired them. They may have found them in an old drawer, or been left them in the estate of a relative or friend. Because they find them difficult to read, they assume that the coins need cleaning. It's much more likely that their glasses need cleaning.
More often than not, right after we have finished telling these people not to clean the coins they have found, they ask us how to clean them anyway! It gets quite frustrating.
Archaeologists, expert numismatists, metal detectorists usually learn which coins may benefit from cleaning, and how to do it. These people will often use an ultrasonic tank. This is not a magic device, it merely uses ultrasound waves to agitate the liquid in which the coins are immersed. This will often be soapy water, and nothing more. Sound waves are gentler than a soft brush.
Many people now own miniature domestic ultrasonic tanks, sold for cleaning jewellery. Before you are tempted to clean your coins in such a tank, remember the advice we have repeatedly give above, if you are unsure - do not clean coins.
Cleaning Coins Spoils the Toning
As we have said for silver coins, it is easy to spoil a pleasing tone, which may have taken centuries to be acquired. Copper and bronze coins will almost always end up looking a brassy unpleasant colour after cleaning. Even gold coins can sometimes be ruined by removing a rich tone which has built up over a long period of time.
As we have made clear above, one of the easiest way to spoil coins is to scratch or abrade their surfaces by using an abrasive. Most cleaning pastes contain abrasive. Any sort of rubbing action should also be avoided, whether using the fingers or a cloth, especially polishing cloths which are impregnated with any kind of cleaning material, and which are usually sold for polishing.
Drying Coins After Cleaning
If you simply have to clean coins after reading this, be careful when it comes to drying them. Any rubbing action will scratch them. Dabbing or patting dry with a clean towel will be the best.Source: 24carat.co.uk