Cleaning coins in ultrasonic jewelery cleaner

Went to the Pawn shop today they had 2 bags of silver coins (Quarters, Halves and dimes), which were way overpriced IMO, 200+ grms for $229.00. Anyway, I took a look at them. Didn't figure face value, but $10 would be a high estimate. Noticed that all the coins were clean, I asked about it and they said they cleaned them in an Ultasonic Jewelry cleaner. I got to thinking about it....and wondered if and how much that would effect value. I don't suppose it would cause damage to them. But I really don't know.
I know cleaning coins is a no-no, but they looked very nice and I didn't see much damage on any of them.

 

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If it is not done correctly, an ultrasonic cleaner can ruin a coin. Junk silver being what it is, they don't care. Sudsy Ammonia also works on junk silver.

 

I wouldn't call these Junk Silver. Most looked like good grades. Was looking at a 1964 Quarter that looked BU/AU as well as some nice dimes. Most I believe were early 60's coins.

 

200 grams would be $8 face.

 

Yes, one man's junk silver is another man's Gem AU/BU!

 

'64 Quarters are so common you can get nice BU ones as junk silver. 200 grams should be worth about $100.00. He is very overpriced at $229.00. Junk silver at 22x face is ridiculous. Even 12x is a bit high but acceptable. Be very cautious.

 

And using an ultrasonic cleaner is not recommended.

 

I wont be buying it. I doubt anybody else will either. just thought it was interesting that they were cleaned like they were. question is, does the ultrasonic cleaning ruin any value the coins may have had otherwise.

 

I believe that is would damage the surface of a coin. Here is something I found while researching the subject. "Note: High power ultrasonic cavitation can fracture the surface of brittle materials and micro-roughen the surface of ductile materials." It is from Donald M. Mattox, in Handbook of Physical Vapor Deposition (PVD) Processing (Second Edition), 2010.

The action of the bubbles and cleaning fluid on the coin and the material removed from the coin re-impacting it can lead to changes in the surface of the coin.

So, to answer your question with a question: Does a change in the surface of a coin change the value of a coin?

 

I was going to bring up cavitation, but someone beat me to it! Anyway, sonication is probably too rough for coins, and probably doesn't do much that couldn't be solved with a simple solvent dip and clean water rinse. The closer the coins are in value to junk silver, the less difference it makes. With enough rough sonication and you're probably losing some metal as microscopic dust into the solvent bath.

 

Thank you all for your input! I appreciate your time and knowledge. I have learned a lot!

 

beerandchips, asked: "So, to answer your question with a question: Does a change in the surface of a coin change the value of a coin?"

So many myths, so little time...

I'll answer answer your question of a question: NO, (if used properly) not in any way you can tell.

PS The first time I was introduced to coins and ultrasonic cleaning was on a tour of a "Boiler factory" selling to telemarketers. Bright BU sells.

 

I would expect that throwing a bunch of coins together into an ultrasonic cleaner would damage them. Their contact points would be vibrating furiously; I'd expect lots of scuffs. Putting a single coin in a metal wire basket would likely do the same thing.

I doubt that a "jewelry cleaner"-class ultrasonic cleaner would cavitate strongly enough to knock metal loose from an intact surface. If it did, it wouldn't be super-great for cleaning jewelry, would it? (Maybe I'm wrong; we certainly do lots of other things to jewelry that we wouldn't do to coins.)

I think that cleaning a single coin in a consumer-grade ultrasonic cleaner (not a high-powered industrial cleaner), suspending it in a fabric net, probably wouldn't cause new damage to its surface. But I haven't experimented yet, so I wouldn't tell anyone else to risk a valuable coin doing it. @Insider likely has actual data.

 

jeffB,

I don't have any data. I have used several different Branson cleaners over the decades. I hold the coins (one-at-a-time) by their edge with plastic tongs. It is important not to let anything else touch the surface. I also agitate the coin continuously so as to remove any bubbles that will eventually bore into the coin's surface.

 

I actually have two ultrasonic cleaners, one small battery operated one that looks like a dentures bath and one 110V model with a metal pan and a dip basket. I don't think there is any ay the battery one could harm coins (done one at a time), but probably wouldn't do any good either. I've been cautious with the other one. I was mainly thinking of using them for heavily encrusted ancients.

 

I've never used an ultra-sonic cleaner on anything. So, what damage might it cause to a silver coin?

 

They can alter the surface of a coin.

 

Collecting Nut, posted: "They can alter the surface of a coin."

Of course they do, that's what they are for...altering the surface by removing foreign matter.

 

You'd want to do that anyway with sudsy ammonia, because the suds come from the SOAP that's added to it, right?

I don't believe in sudsy ammonia, won't have it in the house. If I need ammonia with soap in it, I'll put soap in it. Then again, I do atypical things with household ammonia.