Cleaning concrete from coins?

LordOfTheZincs · Nov 12, 2014

My 43 war nickel has a coating of (I think) concrete over it. It does make sense because it was found right next to a concrete/metal platform holding a huge WWII cannon. I think it was under the dirt and when they were done building the platform they dumped some excess there and it soaked down into the ground. The soil was sandy so it stuck pretty good. I got it scraped down enough to see that it is an S mint mark so no go on the double stamped 43P :roll:

Anyways it took surgical precision with a knife for 20 min. to get it that far. Thought about goof off but will that harm the silver? Thanks :grin:

msand · Nov 12, 2014

Cool little find.

Paper · Nov 12, 2014

I'd look into using a brass brush on a dremel or maybe an SOS pad. Electrolysis? I don't think you are going to be getting much of a display piece no matter how you go about cleaning it though.

ScubaDetective · Nov 12, 2014

http://www.doityourself.com/stry/acid-wash-your-silver-3-pros-and-cons

This might help

Jamflicker · Nov 17, 2014

Soak it in lemon juice then rub with baking soda. You can repeat the process. The black stuff is magnesium that leaches out of the coin while its in the ground. We call them black disks. When we find a black disk we know its a war nickle.

diggininms · Nov 17, 2014

I dont know what itll do to your coin but i know white vinegar will remove concrete from a cars paint without messing the cars paint up.

NectarDetector · Nov 17, 2014

Try soaking it in sugar water... it retards concrete from setting up and can also removed hardened concrete...

joe dert · Nov 23, 2014

maybe vinegar with salt and lemon will do the trick..

hoser · Nov 26, 2014

Try what the rest have said, and if that don't work there is one more option. Heat the coin to somewhere around 300*to 350* and then drop it in ice water. The thermal shock just might dislodge the crust enough to remove it. You may have to do this a few times if it starts to loosen. If you can't get it off any other way you aren't out anything. just a thought. I have seen concrete "pop" from thermal shock.

ohiochris · Nov 28, 2014

Anything acid has potential to remove some of the coin as well , but I know vinegar reacts to minerals like calcite found in sand...so concrete as well. It will usually make a lot of bubbles as the minerals dissolve , so a short soak "should" atleast in theory loosen up parts of the concrete making it easier to get off. Im thinking that silver shouldnt be harmed "much" by the vinegar as long as it wasnt in contact very long....but not positive about that. But after using anything acidic you should then use a base like baking soda to neutralize any remaining acid so it dont keep working on the coin itself.

LordOfTheZincs · Nov 29, 2014

I just realized I have that nickel in a little pocket in my wallet when I took it for show and tell one day.

I'll have to try some of these later tonight, thanks!

Diggum · Nov 30, 2014

hoser said:
Try what the rest have said, and if that don't work there is one more option. Heat the coin to somewhere around 300*to 350* and then drop it in ice water. The thermal shock just might dislodge the crust enough to remove it. You may have to do this a few times if it starts to loosen. If you can't get it off any other way you aren't out anything. just a thought. I have seen concrete "pop" from thermal shock.

That's the one I'd go with! :yes:

Cleaning concrete from coins?

LordOfTheZincs

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msand

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Paper

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ScubaDetective

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