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I agree with Jeff and Doug. One, acetone will not remove AT if the AT is a chemical reaction of the metal. It does a pretty decent job of removing "paint jobs", but will not touch "burn jobs" if you will. I also agree with Doug on "carbon spots". I have only seen one or two real carbon spots in my life, most are like Lehigh's examples of environmental damage. I had bought some jefferson nickel sets with black spots but they were all on the 50-60's coins thankfully. So I just spent them. I have never had those spots on the better dates, so personally I have never experimened with how to remove them. I will be interested in the results myself.

 

I didn't mean scrubbing the coin with salt and vinegar just soaking in mixture

 

I will do this experiment in full.
I'm gathering supplies and making room.
Some may need to soak for a long period of time.

I will say this..
I grabbed a common BU from the album, that had spots.
I dipped it and tried a toothpick to try and remove some spots.
I repeated and repeated to try and get any result.
That did nothing except destroy the luster (as over-dipping does). The spots were not affected.
Keep in mind, dipping is a quick action and doesn't have time to actually act on the spots. So I suspect whatever (if anything) will work, will requires time to penetrate the spots.

I will create a new thread for the experiment when I start.

 

To be just a little more technical:

Vinegar is a mild acid. It will attack various metals, some quickly, some slowly. It also dissolves a lot of oxides, sulfides, and other crud that builds up on coins.

Salt is sodium chloride, and when it dissolves, it produces chloride ions. Chloride ions, when accompanied by acid and/or oxygen, attack metals and crud a lot more vigorously. Platinum and gold will resist almost any chemical attack, but if you combine nitric acid (a strong acid and oxidizer) with hydrochloric acid (a strong acid and chloride source), even platinum and gold will dissolve.

So, if you soak your coins in salt and vinegar, it'll get a lot of crud off of them, but it'll also ruin the surfaces of the coins, very quickly. In fact, unless you rinse and neutralize very carefully, that damage will continue long after you pull the coins out.

 

Vinegar should never be used as a cleaning agent or a dipping agent due to the acidity of it. Vinegar, especially cider vinegar, is actually used by many people to return the date and other details to dateless buffalo nickels. Because vinegar is a weak acid it eats away at the copper content of the coin, which is 25% of the makeup in the case of the nickel, and leaves the nickel alone. This helps to reveal the date on the coin just like nic-a-date would, except that as it affects the entire coin through immersion it doesn't leave the spot over the date that show where it was applied, but it will turn the coin a uniform dull gray. As it eats away the copper the vinegar turns a deep green to green-blue, the water also starts to evaporate from it further concentrating the vinegar. If not careful this color change and concentration change can actually stain the coin or pit it more deeply than just restoring the date.

 

One quibble: I'm pretty sure vinegar eats the nickel faster than the copper. Nickel is much more reactive than copper; it'll displace hydrogen from most acids, while copper won't.

When I left some cull Buffalo nickels in vinegar for weeks, they ended up much lighter (and thinner), and more copper-colored.

The rest of your comments and cautions are spot-on.

 

Ok got it no salt and vinegar for my coins . So acetone is the best to use and just to be sure you can use it on all coins? Also since it may damage coins still with prolonged exposure do you just dip them and wash them off or do you soak them and if so how long? I guess it depends how much crud is on the coin but a general time frame would be helpful.

 

You'll find some disagreement here about whether acetone can harm copper coins -- some people think it can, some think it can't.

You'll also find some disagreement about rinsing with water after an acetone soak. I think the majority opinion is that it's best to just drain off the acetone and then let the last of it evaporate -- it evaporates much more quickly than water, may be less likely to leave spots, and doesn't pose any risk of accelerating corrosion.

I think nearly everyone agrees that you can soak coins as long as you like in acetone, but you need to keep it covered so it won't evaporate.

 

Thank you for your response so what is best for copper coins?

 

I'm personally in the "acetone is fine" camp, but I don't have a lot of experience to back it up, so you probably shouldn't listen to me.

Xylene will dissolve tarry stuff, but I personally don't like working with it, and prefer acetone. It's harmless to copper.

Distilled water is also harmless, cheap, and about as safe as it's possible to get.

 

Thanks

 

I love salt and vinegar actually just on potato chips and fries never on coins

 

Except don't use it on aluminum coins; it'll produce severe pitting (learned that lesson the hard way).

I've also seen it cause discoloration on brass (or maybe it was brass plated, don't remember for sure) coins.

Otherwise, acetone is great for de-gunking circulated coins.

 

As I said, "you'll find some disagreement here".

It may be that some acetone has impurities that will attack aluminum. Chemical engineers, though, say that the acetone in their plants won't attack aluminum. And since they (a) design components to handle it all the time, (b) keep a close eye on those components to make sure they aren't being attacked, and (c) stand to cost their companies millions of dollars if they get it wrong, I go with what they report.

Maybe the lesson here is "whatever you use, test it thoroughly on something cheap before you use it on anything valuable."

 

Perhaps there's a purer form of acetone than what's available at my local Home Depot, but probably not worth my effort to source it. The damaged coin was a cheap-y and one of very few aluminum coins I ever expect to pass through my collection, so no great loss.

 

...and I guess I'm back to "acetone on copper probably isn't a good idea".

I sure wish, though, that the citation could be more specific about "ambient light". I wouldn't be a bit surprised to find that the effect doesn't happen under incandescent light, happens slowly under fluorescent light, and happens quickly under sunlight. If so, that would help explain why some people don't encounter the problem and others do.