Cleaning advice - pennies turned dark brown. Help !

[Trunkman]

I just bought a rock tumbler and threw some modern pennies in there that I recently dug up. The pennies were pretty stained/dirty. I put in a couple of tablespoons of vinegar, 2 tablespoons of CLR, a half teaspoon of salt, a little Dawn, gravel and a quarter cup of water.

I checked the tumbler every half hour and the just kept getting darker until they became dark brown. I don't get it. I watched some videos, did what they did, but got terrible results. I then tried it with just gravel, salt and vinegar - no better. See pic.

Any advice on how to get these back to a copper color would be appreciated as well as tell me what I did wrong. Thanks.

 

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[GoldieLocks]

You may have stripped the copper off the pennies says my partner the chemist. (It's OK, they were just pennies.

 

[pat-tekker-cat]

We use Creme of Tarter to tumble crusty coins.
Throw in some pea gravel or aquarium gravel,
some water, and about a tablespoon of tarter.
You don't have to burp the tumbler either.
It should bring them back to copper color.

Only draw back, when doing silver color coins,
don't let even one penny get in there!
It'll turn them all dark and you'll have to tumble them again....
without the penny in there.

I usually get the big bottles of Creme of Tarter from Aldi around holiday time,
instead of the little bottles at the grocery store.
Hope that helps.

 

[Clad2Silver]

I just bought a rock tumbler and threw some modern pennies in there that I recently dug up. The pennies were pretty stained/dirty. I put in a couple of tablespoons of vinegar, 2 tablespoons of CLR, a half teaspoon of salt, a little Dawn, gravel and a quarter cup of water.

I checked the tumbler every half hour and the just kept getting darker until they became dark brown. I don't get it. I watched some videos, did what they did, but got terrible results. I then tried it with just gravel, salt and vinegar - no better. See pic.

Any advice on how to get these back to a copper color would be appreciated as well as tell me what I did wrong. Thanks.

Try shaking them in some liquid bowl cleaner for a few minutes, then tumble them in soapy water for an hour. Also, use more gravel.

 

[ticndig]

give them to the tax man dirt and all.

 

[Trunkman]

Thanks for all the advice. I gave all of them a try and most of the discoloration is gone. They look for like pennies now. Off to the tax man!

 

[mick56]

I only use Dawn with gravel. The other chemicals can react with the exposed zinc on the newer cents.

 

[Back-of-the-boat]

I see what looks like a token in there also the coin that says Sugar sand something. That was probably a different metal and could be what changed the color.

 

[Treasure_Hunter]

I use dish soap and and aquarium gravel, works great.

 

[Trunkman]

I tumbled them with dawn, water and gravel only. Did this two more times and now they look pretty good. Thanks everyone!