Cleaning Coins with a Ultrasonic Cleaner

Still it is kind of scary to me because of the possibility of creating a matte kind of surface on prviously smooth areas.

 

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That's why it's expert-level stuff. It can and will sandblast the surface of a coin, and it's more likely with nicer fields than worse ones because the flatter the field, the more likely such minute damage will add up to something visible.

 

After thoroughly reading this article I have determined Ultrasonic Cleaners are above my pay grade. I think I will refrain from Ultrasonic Cleaners until I can understand the effects... Long and short of it Don't Use Ultrasonic Cleaners to clean coins

 

Realistically there's no need for the technology except for the most difficult encrustations; I could see myself making more use of it for dug Ancients, for instance, if I were into them. For the overwhelming majority of conditions making you *think* you want ultrasonic, the freezing/cooking cycle I'm so fond of works just fine as long as you're not into instant gratification.

 

My feeling for a reason to clean a coin is a matter of economics. If can be determined the coin has some PVC or light dirt or unwanted toning and not seriously corroded the appropriate chemical can be used. Sometime cleaning a coin may turn up what others have attempted to hide(Real Bummer). My experience with Ultrasonic Cleaners have turned up a wide variety of unpredictable results my recommendation for coins of value is never never never use with an ultrasonic cleaner send it to an experienced restoration expert. As shown in the forum even that does not necessarily guarantee good results just different results.

 

OT: I dont know.

But if I was to use one, the pan would be lined in something softer than the coin itself to help keep the coins from being scratched. Maybe ABC plastic?

 

One from the Pro Tip Library (one of a number of solutions, all of which individually affect how you employ the transducers differently): Basket-weave monofilament.

Remember, the "ideal" way to expose a coin to an ultrasonic vibration is to suspend it alone in a magnetic field so nothing whatsoever is touching it. Whatever the coin is touching while the transducers are running will affect the cavitation in that area, and even though you could correct for that, the correction would adversely affect the open areas of the coin. The key to consistent results is consistent application of the bubble bath (which is what I call it ). You only do one coin at a time, you minimize that coin's chance of contacting something "solid" while being vibrated, and (I hate dribbling information out like this) the more contact the coin has with other things, the more you need to vary the frequency and orientation of the coin during the process.

The ideal weapon for numismatic applications is able to vary the transducer frequency between 40kHz and 120kHz, while at the same time having accurate temperature control of the solution up to 100C. Unfortunately, that weapon doesn't really seem to exist; if I want one I'll have to build it myself. They aren't really that complicated; you could for instance rework one with the right sort of solution control using custom transducers....

 

Ha!!!! I go it!!!

Lots of patience and hold the coin by the edge in the solutions. This way you'll clean the dirt from under your nails at the same time

 

There is a problem with ultrasonics I would like to bring to your attention which is why I won't use them on a coin that has any significant numismatic value (you would have to determine what that is to you).

This regards leaving them in for a LONG period of time...you will have to test to see what that is on your machine. Most have timers that go up to an hour, which is too long. Always do testing first on a coin that has little or no numismatic value.

On Lincoln Cents for one, I have seen the letters for LIBERTY as well as the date receive a lot more attention from the ultrasonic action than the surrounding area. Those areas actually lost all or most of their patina in the ultrasonic process. Other impacted areas with sharp relief (especially scratched areas) also suffer similarly.

So, if the coin has any sharp relief in any of its details, those areas will likely lose their patina from the ultrasonic action if left in long enough. Definitely don't use on any rare coin!!! If the value of the coin is less than $2.00, I say use your better judgement on what you would rather have...either the value of the coin which is better if left untouched or what it looks like to you.

The only solutions that I've seen which were acceptable to the numismatic associations are professional cleaning of virdigris by professionals.

 

Based on my experience with this, I have only used it on coins that I found metal detecting on the beach and it just removed some superficial dirt. All coins still look like they were buried in sand.

 

@SuperDave Just resurrecting this thread a little as I see a lot of negative comments surrounding ultrasonic cleaning but I'm wondering if it is possible with caution.

So i've been testing, and yes there are issues with metal baskets and such, but otherwise on gold coins I don't see any drawbacks as of yet.

I've placed a sponge cloth on the metal basket with slits just a little smaller than the coin so that it bridges and still allows the waves to form. This with a pH neutral surfactant (actually an enzyme based one), do you think that's an ok method?

I did try some other cleaners but once the dirt removed there was a copper colour (22ct gold coins), and though I think this is toning caused by the dirt I'm now trying some others to rule that out

 

@SGSG
Superdave was last seen on CoinTalk December 14th 2017

Many members either leave or move on to a better place over the years. It's called life.
But thanks for your post.

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