If you are a metal detectorist or treasure hunter you will surely have found some coins that you cannot read or identify. Or maybe you have been digging some foundations in the earth and found a coin that is dirty and corroded?
Well this is the coin cleaning guide for you! In this coin cleaning guide by Magnet Fishing Pro I am going to teach you several ways of cleaning old coins that otherwise would be impossible to ever read or identify. I will show you some less intrusive ways to gently clean coins and some more last resort ways for the stubborn ones. Hopefully by using this guide and choosing the correct method you will not devalue your coin.
First off let’s talk about why your coins are so corroded and discolored, then we can get an understanding of the ways we are going to be cleaning them.
Why do coins corrode and degrade?
When we find coins be it with a metal detector or other means it is usually certain that it has come from the soil or the beach.
Both of the above environments fountain salts and other minerals that are both acidic and alkaline. These chemicals over time will cause reactions with the metals and as such corrode, rot or tarnish the coins.
The vast majority of coins themselves are made from a mixture of different metals and elements and as such are always trying to get back to their base metals. The only coins that do not react to the chemicals in soil and saltwater are gold and to some extent silver. Gold is chemically inert and as such does not react with any other chemicals. Silver however does react but is much less susceptible to corrosion than metals such as bronze and copper.
Are there some coins that you should not clean.
When it comes to cleaning coins you really need to know what coin you are dealing with. Some old coins can be very valuable and any cleaning may devalue it.
It is always best to consult a professional before attempting to clean any coin that you think may be rare or valuable. If in doubt do not attempt to clean the coin.
How to clean gold coins.
If you are lucky enough to find a gold coin then have my serious congratulations! However please do not attempt to do any serious or aggressive cleaning on your coin.
Gold is a non reactive metal and as such you should find that a gentle rub under running water should be enough to clean off any dirt or debris.
Once this has been done you should find that your gold coin looks as good as new and no further cleaning will be needed. If it still has any corrosion the chances are that it is a fake and maybe a gold plating on top of a base metal coin. This was quite a common practice used to cheat the system years ago.
The best way to clean silver coins.
If you find a silver coin then the chances are that it is an old coin. Most countries stopped using silver as a currency years ago as the value of the metal exceeded the value of the coin itself.
Please be aware that some silver coins can be very old and very valuable and any excessive cleaning can reduce its value substantially. If you have any doubt about the value and identification please seek the advice of a professional.
If however you are certain that your coin is not very rare and valuable there are a number of ways that you can clean your coin. One of the easiest ways to clean your coin is the spit and foil method.
I want to be honest at the start, it is pretty disgusting but it will get the detail of your coin showing very quickly and effectively. The way that we do this is by using some aluminium kitchen foil and yes, you guessed it, some spit!
Place the coin on a piece of foil that is around 4-5 times the size of the coin. Now place a bit of spit on top of the coin in the foil and fold the foil over to encapsulate the coin. Use a gentle rubbing motion to start the reaction and help with the cleaning.
If your coin is silver you should feel heat being produced by the chemical reaction that is taking place. Also there will be a nasty eggy smell coming from your little experiment.
The spit, silver and foil all create a chemical reaction that eats away at the black tarnish that coats old silver coins. After a few minutes you should find that all of the tarnish is removed and your coin is all shiny once again.
Using electrolysis to clean silver and old bronze coins.
This method is quite an aggressive method and should not be used on anything that is mega valuable or rare. It works an absolute treat on old but non rare roman silver coins and many of the more modern silver coins.
It also works very well on old bronze coins that are completely rotten and otherwise ruined. Beware though you need to keep an eye on your coin when it is in the electrolysis bath as it does not take long to go from good to bad.
Electrolysis works by using a small electrical current through a slightly saline solution. The coin is placed in the water and the solution plus the electric current react to the metal causing any of the dirt and debris to come away from the coin.
Without spending a lot of money on some very fancy kit most people will make their own home made electrolysis kit fir cleaning their coins. It is a fairly simple kit to make by using an old phone charger cable and a metal conductor such as a nail.
Cleaning coins with a coin tumbler.
This next one is possibly the most extreme form of coin cleaning that there is. A coin tumbler works exactly as the name suggests! Coins are placed into a small barrel tumbler that is connected to an electric motor. You also place a small amount of abrasive material into the tumbler usually a coarse sand and then switch it on.
The tumbling action and the abrasion on the coins from the sand will leave your coins grime free and will also remove much of the corrosion. As good as coin tumblers are I do not recommend them for any really old coins or valuable coins that are made of gold and silver, it will ruin them.
What coin tumblers are perfect for cleaning is modern coins and some of the pre-decimal coins that have no value. Generally all the coins that you find on the beach that you want to change from a wreck to a spendable coin again! It is also good for cleaning metal detecting finds like buttons and other small items that are not to delicate.
If you would like to see my recommended coin tumbler and the one that I use myself then check out this link which will take you to the Amazon listing for it. It is a really good coin tumbler and does what I need it to do.
Using an ultrasonic cleaner to clean coins and metal detecting finds.
This is one of my favourite ways to clean old coins that are difficult to read due to corrosion and dirt. It is a very efficient cleaner and does a great job.
How does an ultrasonic cleaner clean coins?
Ultrasonic cleaners work by using cavitation bubbles. What this means is that very high frequency pressure from sound is used to agitate liquid such as water. When the water is agitated like this it cause substantial forces on the surface of any item placed into the liquid. This high pressure actually strips away and removes any of the surface contaminants such as dirt, corrosion and discolouration. The great thing about it is that it also penetrates gaps and cracks in the coins that are placed in the liquid.
I find ultrasonic cleaners to be a great way to clean coins and artefacts and it is one of my go to methods for cleaning. Here is a link to the one that I use that is a good price on Amazon.
I really hope that this coin cleaning guide has helped you choose the best method to get yours old coins cleaned without devaluing them. Each of the different methods have benefits depending upon the coin and how encrusted it is. I would just like to say again that if you are in any doubt about the coins value or rarity please do not attempt to clean it. Instead seek the advice of a professional as they will be able to advise or even clean it for you.
My name is Andy and I have been a prominent figure in the treasure hunting world for coming up to a decade on various platforms such as YouTube and blogger. On Magnet Fishing Pro I like to share my wealth of knowledge and experience in the form of guides and blog posts to help you progress in the hobbies of magnet fishing and metal detecting. You can read more about my treasure hunting journey in my About Me page