Cleaning Coins with a Ultrasonic Cleaner

Would the grading companies be able to notice if a coin was cleaned with a Ultrasonic cleaner with no solvents?

 

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Good question. I have never seen one of those. I can see it more useful for Metal Detecting coin finds.

 

My wife has one of these to clean here jewelry .

This machine vibrates and will scratch your coins too ..

 

I've known people to use them. Only thing you have to worry about would be scratches in terms of tpg detection. Try it with crap coins first of various compositions and check em with a loupe after. I think some people put a velvety type material on 5he bottom of the basket just in case

 

That, and one coin at a time I think would be safe.
But it's still just a treatment for debris on a coin, not for ugly marks or toning.

 

I've seen suggestions in this and other forums about the use of acetone as a pH neutral solvent to soften verdigris on coins. I have used it to remove dirty grease, shellac, varnish and other organic matter. Since acetone is also water soluble it removes salts that could cause corrosion. Compressed air to remove the soften verdigris leaves no micro scratches. However, this should be done outdoors with good ventilation and chemical resistant gloves as acetone is highly flammable and somewhat toxic.

 

Acetone has virtually no effect on vertigis. And compressed air seems way too subtle to remove anything effectively no matter how "loose" it is. Verdicare is what should be used on verdigris and a Q-tip, a toothpick or a rose or citrus thorn as the agitator but use it while the coin is still immersed in the fluid, be it acetone, xylene, baby oil or verdicare and it will act as a lubricant to lessen the likelyhood of micro scratches from the toothpick, thorn or Q-tip

 

Ultrasonic cleaners are rather like hunting squirrel with a cannon. You'll get the job done, but maybe not much will be left of the original when you're finished. It is a violent technology capable of damaging a coin as easily as cleaning it, and I personally don't employ it except as a last resort for heavily-encrusted pieces which have not answered to less-intrusive methods.

 

Yes they can. On Lincoln Cents you'll see a shinny metallic sheen on the surface on the coin.

 

Great documentary Comixbook. It gives us an idea of what works and what doesn't on our experiments. BTW, you did an excellent job on the project.

 

no way would I do this. prepare for scratches.

 

If an ultrasonic can knock tartar off your teeth I am sure that it can do more than a bit of damage to coins.

 

Ultrasonic cleaners work using collapsing cavitation bubbles in liquid. They're tiny, but the bubble collapse generates 5000 degrees Centigrade and a velocity of 500mph. One can expect an ultrasonic cleaner to wear through its' own container during its' lifetime; imagine what it could do to a softer metal coin if misused.

There's a number of coin-specific considerations to employing ultrasonic cleaning, and it's only more effective than far less dangerous methods in a few niche cases. Nothing I'd use "regularly" for conserving coins.

 

From what I have seen, ultrasonic cleaners will STRIP the surface, not of verdigris or any other corrosion damage, but definitely of dirty stuff. The problem is that it can leave a granular appearing surface on older/worn coins. For Uncirculated or Proof coins, as long as there is nothing for them to bump into, it would probably be OK. Like others said, try it on coins you don't care much about at first.

 

Just wondering if you are quoting some source?

 

Well, the physics of cavitation are pretty well known; here's something from an ultrasonic cleaner manufacturer:

http://www.tmasc.com/qa process.htm

 

Interesting, thanks for the link. Looks like there are quite a few adjustable parameters with these devices.

 

The only coin I ever had that I know was cleaned by an an ultrasonic cleaner was a 1913-S 25c I had submitted to ANACS. They told me that there was too much crud around the mintmark so they asked if they could clean it ultrasonically to make the determination as to its authenticity. I gave permission, they decided it was a genuine piece, and I never liked the look of the coin after that. So much for ultrasonic cleaning!

 

I forgot to mention, the coin was a G+, with perfect color for a well-circulated piece. That is, the color was perfect before the cleaning but not after.

 

Yes. For numismatic use, you'd want one in the higher frequency ranges - 80kHz and up - as they create finer bubbles capable of cleaning tiny interior detail. Temperature is a critical factor, and one has to consider how to suspend the coin without it contacting anything it can bounce off of, without interrupting the cavitation action.

No reason why one cannot employ ultrasonic cleaning for more careful/valuable conservation jobs, but it's definitely expert-level tech in this usage.