A large copper - how to clean it properly?

[brianc053]

Hi everyone. I went back to the farm again this morning before work and I was lucky enough to locate this large copper with a lot of green patina on it.

Right after digging it I decided to control myself and NOT just wipe off all the dirt, because with past coppers from this location I've lost the green patina - and some of the image from the coin - by cleaning the dirt too aggressively.
At the car I used a toothpick to remove the large amounts of dirt and I gently used a toothbrush to start to clean one side, and I did NOT recognize the image as a US Large Cent - so I immediately stopped any further cleaning. (It may have been Britannia from a KG that I saw, but I'm not sure yet.)
I actually grabbed a handful of mud and put the coin in the mud, and then in this plastic shell that I had in the car, and brought it home.
The coin is still in the mud in that shell.

So - how should I properly clean this coin? What are the steps I should take to try to keep as much of the green patina and as much of the images on both sides as possible?

I'm going to show self-restraint here and try to do this one right.

Thanks in advance for your advice.

- Brian

 

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[brianc053]

When I have a coin like that I will rub it aggressively between my finger and thumb using a wet paste of baking soda. I will also use a pencil eraser. The smoother you can get it, the better it will look.

Thanka Steve, I haven’t tried those methods before. I will try them!

 

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[diggerdeeper]

Not sure if anyone suggested it yet, but sometimes hydrogen peroxide will help remove green corrosion without harming the base metal.
Some guys heat it up, which I suppose makes it more chemically active; and even though it's not an acid.. I'd be careful of breathing any fumes.
Good luck !

 

[brianc053]

Not sure if anyone suggested it yet, but sometimes hydrogen peroxide will help remove green corrosion without harming the base metal.
Some guys heat it up, which I suppose makes it more chemically active; and even though it's not an acid.. I'd be careful of breathing any fumes.
Good luck !

Thanks digger. I've used hydrogen peroxide on other coins and it's caused (or revealed) pitting in the coin, and I'm worried about that with this one. You mentioned that it won't harm the base metal, so is it safe to assume that hydrogen peroxide will only reveal pits, it doesn't create them?

FYI I've also used electrolysis in the past on corroded pennies, and I know that electrolysis does harm the copper and creates pits. I don't plan to do that with this coin. (I don't have an "ugly box" - I just have a AC-to-DC adapter that I cut the round thing off of and attached two alligator clips to.)

- Brian

 

[brianc053]

Quick follow-up: I put together a short (5min) video of my cleaning methods (Andre's Pencils, toothpick, toothbrush).
I thought some of you might be interested in seeing what I tried. And I'm happy to hear critiques or suggestions for improvement from you experts out there.

It's become clear that this is a very corroded Draped Bust, so I can't really do much harm to it. At this point I'm just trying to get it to the best possible condition before putting it in my 2021 catalog of finds.

Thanks again for all the input everyone.

 

[cannonball]

I use coincare on all of my dug cooper coins. It's inexpensive and it conditions the coin. I use a q-tip dipped in coincare. Look at some of my coins done with just coincare. It will not hurt the coin surface..
.

 

[pa-dirt_nc-sand]

For a rough coin like yours, but some definite details in the base metal, I would try the following. 1. Bath in hydrogen peroxide for a couple hours. 2. Let dry, heavy andres pencil 000 steel wool rubbing 3. Repeat as necessary

If this does not get the patina crust off, try adding an additional step of 10 minute bath in acetone (nail polish remover), this sounds harsh but really just hyper dries out the coin making the andres and peroxide work a bit better.

If this does not get the patina crust off, try very light electrolysis (like old cell phone charger) for 30 seconds, dry and andres pencil rubbing. Caution here, if the electrolysis is too strong it will expose and magnify all the coins imperfections and cause it to be new penny bright. So less is much better. This is sort of the last ditch effort, no turning back stage.

Good luck.

 

[brianc053]

Pa-dirt, here’s where the coin stands tonight after additional attempts with just baking soda, water, toothpick and Andre’s pencils.
It looks like it’s time for hydrogen peroxide as you suggest.

I’ll let you know how that goes tomorrow.

 

[Coinstar magnet]

That's a nice set up for cleaning...