The great thing about silver coins is that they usually come out of the ground perfect. I love to see that shiny silver sticking out of a plug in the ground. Usually just washing them off quickly with water is all you need to do and no real work is required. Just another thing to love about digging silver.
Occasionally, however, we dig a silver coin that has some type of black gunk all over it. Something that resembled concrete gum. Recently I dug an 1890 seated dime with this problem. It was difficult to clean, but using this process, it looks completely clean.
– Baking Soda
– Aluminum Foil
– A metal boiler or pot
– A glass bowl or smaller container that can fit into the boiler or pot
– Salt (preferably Sea Salt)
– White Vinegar
– Tongs or something to remove and flip the coin
How To Proceed
1) Put enough water in the pot to cover about 2/3 of the glass container and start to bring it to a boil. .
2) Fold aluminum foil dull side out and put it at the bottom of the glass container
3) Put 1 cup water, 1/2 cup white vinegar, 1 tablespoon Baking Soda, and 1 tablespoon Sea Salt in the glass bowl/container. You don’t have to use Vinegar, but it speeds up the cleaning
4) Put the coin on the aluminum foil. Press it into the foil for maximum contact and best results.
5) Carefully place the glass container into the pot and wait until the mixture in the glass starts to boil.
The chemical reaction will cause the gunk to transfer from the coin to the foil.
6) Take some tongs and remove the coin after 10 minutes or so. Rub it with a paper towel to remove excess loosened gunk and then put it back in. Alternate sides as necessary.
Repeat step 6 until all the gunk is gone! If the coin is completely covered, this may take quite a bit of time. You may want to start with a clean mixture with a new piece of aluminum foil if it seems the cleaning process is slowing after quite a while.
Sometimes when coins are really black, it is due to a reaction with the soil that caused impurities to leach out from the silver. Once the gunk is removed, this may leave some slightly unsightly pock marks in the silver. This is not because of the cleaning process – this is due to the reaction with the soil.