Ultrasonic Cleaner - Before And After

I've used the ultra sonic cleaner on numerous world coins with good results. It's amazing how absolutely filthy they are raw- I swear they are retrieved from bathroom floors worldwide.
I've used the ultrasonic with hot water and DAWN dishwashing soap to remove the utter nastiness from the more interesting coins with great success. I also used it to remove what turned out to be nicotine deposits from a batch of Peace dollars I owned for awhile.
I'll confess I've never quite grasped how allowing a coin to languish under decades-in some cases centuries-of dirt, grime, oil and that sticky stuff on movie theater floors somehow makes it more valuable or desirable. I get the whole "no metal removal" bit, but allowing dirt and corrosive substances (like salt) to remain seems contrary to "conserving" for future generations.

Scared to clean coins ... justified ?

I have seen some pretty inexpensive ultrasonic cleaners at places like Bed Bath and Beyond. Does the cost of the ultrasonic cleaner have a direct relation to the effectiveness of it? Or do they all pretty much do the same thing? I was actually looking to get one, as I have many coins that are just like the ones posted here and very difficult to improve with acetone and VC.

Here are two more experiments, both silver. In my experience:

Copper-nickel coins are almost always safe. Whatever is left behind will still look better than whatever was originally deposited there.

Copper is usually worrisome, don't submerge it for too long and be prepared for pink exposed patches that were previously covered by dirt. However copper coins are also most likely to need cleaning because their low value leads to greater mistreatment.

Silver is really a mixed bag, because black dirt looks just like black tarnish. A mix of dirt and tarnish will be revealed to you whether you like it or not after the cleaning, and the exposed patches will tone faster than the rest of the coin. I have an ongoing experiment; a 1870 silver 2-peseta coin from Spain that I cleaned in September 2014, which always sits out in the open on my desk. The ultrasonic patches started out very light compared to the rest of the coin's moderate tone; they soon turned interesting colours and indeed these seem to change hues about once a month. When aluminum or titanium or niobium is anodized, an "artificial" layer of oxide is quickly created through electrical current. The layer's thickness directly correlates to the colour of the metal. So, my assumption is that the changing colours show a rapidly increasing layer of silver sulfide. My hope is that eventually these patches will catch up to the rest of the coin and I'll have achieved perfection. (I'm trying a similar experiment with that Latvian coin.)

Never tried gold, but considering it's not chemically active an ultrasonic cleaner should do nothing but improve it. Still, you should have a plastic basket, as a metal basket would scratch the coin badly.

Anyway...


When I got this coin, I knew it was cleaned, but it was also dirty, especially above King Leopold II's portrait. (Couldn't the person who cleaned it have tried to also remove the dirt...?!) The look of the coin totally changed when the dirt was removed. Considering it comes from a place where your hands would be cut off if you looked at a white man the wrong way, I'm at least glad that any mysterious substances have been removed.


This Southern Rhodesian crown was nearly perfect, but it had a little bit of green around the rim. The ultrasonic removed that perfectly. You can also see how the entire coin brightened up just a little bit.

It's been some months but I have some more results. Looking through bins of world coins really shows you the hundreds of fascinating ways a coin can become butt-ugly.


This Yugoslav coin turned green. Some of that green is now gone - further ultrasonicing might be able to shake all of it.


Finally! Favourable results on a silver coin. This dark-toned Iraqi piece became uniformly lighter and more attractive, without having any inconsistent untoned spots revealed. Wonderful.


This Hong Kong silver was begging for a clean as it had a spot of caked-on crud. This is the kind of removal that the ultrasonic machine excels at and it's also a nice demonstration of the discolouration that will usually be underneath any really dirty patches.

Nice animations to show the differences. Thanks for posting this info.