Cleaning old coins

Cleaning old coins might seem like a good way to revitalise the appearance of a treasured item, but could in fact reduce a coin's value significantly, and should be avoided. Particularly in the case of old precious metal coins, cleaning them is most definitely not recommended! Many British coins, especially those from 1946 and earlier, could contain silver, and in some cases perhaps gold. Cleaning old coins from before WWII then should be carefully considered first, and time should be taken to identify the coin, so you can be sure what metal(s) it contains.

Gold and silver have been the metal of choice for coins for millennia. As a noble metal, gold is nonreactive, and does not corrode as a result. This means in theory a gold coin even from 1,000 years ago will look largely the same as it did when freshly minted.

In reality though, time takes its toll even on a pure gold coin. Whether from being handled during day to day trade, or perhaps buried underground for safekeeping, an old coin will likely lose some of its lustre over time. Dirt or grime inevitably build up, especially in the raised edges where the design has been struck. Even tiny scratches, slowly becoming more numerous over time will inevitably take the shine off an old gold coin.

As pure gold is soft, it would be unsuitable to use for any circulating coins, and traditionally 22 carat (91.67% pure) gold would have been used. This means copper or silver (or indeed another metal) could also be found in the coin. These will react over time, tarnishing or changing colour, which can also make them look like they might need cleaning.

Silver coins can suffer from the same problems as noted above for gold coins, but silver can also develop a ‘patina’. A patina is also commonly referred to as tarnish, and is found on the majority of old silver items. Unlike gold, silver does react to sulphur found in the air, and develops a dark-toned outer layer. The silver beneath remains protected, and many people enjoy the contrast a patina adds to a silver coin, but it can look very different to new silver coins seen today, causing concern to those who don't know what it is.

As seen in the image above, all three silver coins are dark-toned, with just hints of the original silver poking through. The effect is a stark contrast between the design and the background of the coin. The silver underneath remains protected, with just a thin outer layer of the tarnish.

Whether it’s a build-up of dirt and grime on a gold coin, or the patina on a silver coin, it might seem harmless to clean these old coins. As we discuss below though, it is better to leave coins in the condition you find them whenever possible.

Should you clean old coins?

In almost all situations the answer is no, you should not clean old coins. When a coin is graded, the condition of the coin does not include its cleanliness. Collectors of old coins will fully expect a patina to have developed, and most will appreciate the appearance.

‘Toning’ is a phrase often used when describing old coins, as they can take on additional beautiful tones as time goes by; green, copper and even blue hues can enhance a coin’s appearance further. The coin pictured below for example is an American silver Quarter-Dollar that has taken on a striking blue tone.

Cleaning an old coin would remove the patina or toning that helps make it even more unique and visually appealing. Removing this effect can significantly reduce the value of the item.

The other main reason you shouldn’t clean old coins is that you can easily damage them. Most coin cleaning products are abrasive, and could damage the coin. Non-abrasive chemicals can still react with the other metals found in some old coins. The physical act of scrubbing or polishing can also wear down the design, destroying one of the most important factors in deciding a coin’s grade. If you use a rough cloth to try and dry the coin this can also add scratches to the surface - another unwanted blemish.

Even for newer bullion coins, the value is in the precious metal content, not the cleanliness of the coin. So, when you next see an old coin that looks a little dirty, save yourself the tedious job of cleaning it.