It is always suggested that metals, specifically coins found during the process of metal detecting if cleaned, can diminish its value. This is because; the sand and mud particles act as sandpaper for these coins. So when the coins are cleaned, these sand and mud particles leave scratches on it thereby reducing its value. So if you are cleaning your coins or any relic by your own methods, then the mind set should not be to sell them.
Approach towards cleaning the discovered treasure
The best way of cleaning the old silver coins is to put water on the coin and later dip it into the baking soda that attracts all the soil particles without leaving any scratch marks on the coin. There are various other chemicals in which the metal could be dipped in for some time to remove all the dirt particles present on them.Generally, as far as the coins are concerned, they are prominently formed of three different metals – nickel, steel and copper. They all can be cleaned the same way but not together in a chemical solution. Else the nickel and steel coins would also get copper colored and reduce its value.
These metals can also be cleaned in a mixture of salt and vinegar which is quite commonly accepted. But it should be done in a well oxygenated area, so that the salt particles break into sodium and chlorine gas that escapes away as chlorine gas is a harmful element capable of corroding the coin.
Different metals – Different conditioning
Metals found beneath the ground are cleaned in different ways, because they react differently with soil particles and its elements and the elements of air. Like, iron and steel gets rusted by oxygen, they are generally cleaned by placing a protective coating over it when they are taken out to prevent its direct touch with the oxygen in the air.
But copper items are treated by dipping it in lemon juice or alcohol. This removes their initial layer of dirt post which they are treated with a solution of water and baking soda that attracts the remaining dirt without hampering the metal and its quality.
Moving onto precious valuables, where gold coins and jewelries do not really require any cleaning method because they are not that reactive to air or soil elements, silver requires a step by step procedure to be cleaned.
The crux of the situation is that whatever is the discovered relic formed of, either you as an individual enquire a formal and specific procedure of cleaning, or take it to an expert for it. This way you could stop the value of the relic from contracting.
Weather you have an intention of selling the relic or keeping it with you, there is no harm in maintaining its value, when it was maintained for long times beneath the earth. There are cleaning procedures and solutions available for every type of relic. So make use of it and play safe.