Ultrasonic cleaning - yes or no?

[ambr0zie]

Hello ladies and gentlemen,

I am not an expert in cleaning coins. Actually, on some occasions I ruined some. My only positive results were on some coins with horn silver (using thiosulphate) and some MINOR bronze disease - but I am still inspecting these ones from time to time. 

I know about ultrasonic cleaning but I am not very familiar with how it really works (not technically - I mean real results). I ordered myself a very cheap device (I am ashamed to mention the price) - I had a very small voucher for a local website and I saw the cheapest ultrasonic cleaner, battery powered, so I ordered it. 

I do not expect spectacular results but I wonder if ultrasonic cleaning (not necessarily done with a cheap device) is a good cleaning method. Would it remove earthen deposits? Is it dangerous (note - I do not intend to use it on very thin coins to avoid any damage). I also intend to use it with distilled water only - and perhaps with baking soda, thiosulphate - the substances I used before and I know they are OK. 

I know for sure the device will NOT arrive with instructions. So I would be grateful if somebody who uses a similar device can help with a "walkthrough" - what kind of "dirty" coins are suitable, how long should a coin be left, any precautions. 

[Kaleun96]

In my experience, it won't remove any hardened deposits or toning but it will shake loose any dirt that's hiding in cracks, crevices, and pores that would be missed by cleaning the coin with a toothbrush under running water. I would also advise using it against any coins with porous/corroded/rough surfaces (as visible through a 8-10x loupe) as I'm unsure whether ultrasonic cleaning may actually make the surface slightly worse. I'm unsure because it's difficult to sometimes tell whether the dirt that was removed by the ultrasonic cleaner out of the pores has just made it appear as if the pores were larger, or if the pores were slightly enlarged by surface material flaking off.

For those reasons I'd also avoid crystallised or plated coins.

There is one coin where I used the ultrasonic cleaner predominantly to clean the coin. You can see the results of that here. Unfortunately the photo I took of it pre-cleaning wasn't as high resolution as my normal photos so it's difficult to compare some of the minor differences. I think the large majority of "pores" that seemingly appeared were actually just previously covered by deposits, but in a few places I suspect some weakened surfaces were removed at a microscopic level.

For that treatment, I did all sorts of testing but only did "spot" checks after, i.e. taking a photo of a specific part of the coin. So it's now hard to compare what exactly did what. In terms of length, generally if you don't see anything happening within the first 15 seconds, I doubt much will happen at all. I did do some 10 minute sessions but after seeing little benefit to those, I now keep most to under 60 seconds. I rarely use it these days though since most deposits I'm able to clean using other methods.

In terms of liquids/solutions, I think you do see a slight improvement when using "ultrasonic cleaner". This has proved safe enough for silver coins I've tried it with. You can also just try warm water and dish soap as that works nearly as well. Within the ultrasonic cleaner, or at least on mine, there seem to be "hot spots" where perhaps some vibrational waves meet and form an area where you can actually feel the vibration in the water. I generally try placing the objects in these spots but I don't know if it makes a difference.

Lastly, to finish things off with a video, here's a coin that I had just cleaned with thiosulphate to remove some horn silver but as some deposits remained, I decided to throw it in the ultrasonic cleaner. What I think happened is that the thiosulphate softened/dissolved some of the horn silver hiding in the porous parts of the surface that wouldn't come out from normal cleaning. The downside is that it revealed just how porous some parts of the edge were but it did also reveal some extra detail on the portrait.

Headphones warning: the sound of the cleaner can be quite irritating so you may want to mute the video / your speakers.

 

Edited February 7, 2023 by Kaleun96

[ambr0zie]

Extraordinary, @Kaleun96. Appreciate your reply. 

The device I bought is very likely a toy. To give a clue, with the price I paid is less than the starting price for a coin in a budget auction 🙂

I intend to test it, of course, on a zero value modern coin with gunk on it. 

[Kaleun96]

11 minutes ago, ambr0zie said:

Extraordinary, @Kaleun96. Appreciate your reply. 

The device I bought is very likely a toy. To give a clue, with the price I paid is less than the starting price for a coin in a budget auction 🙂

I intend to test it, of course, on a zero value modern coin with gunk on it. 

I guess mine might be the starting price of a coin in a mid-level auction house, I have this one 😁

[Phil Davis]

29 minutes ago, kirispupis said:

I nearly want to cry when seeing the Lysimachos tet reverse.

To each their own, obviously, but I strongly disagree. I try to think in terms of what the die-engraver might prefer to put in his portfolio for a job interview. From that perspective, the Lysimachos in particular turned out rather well. Ugly/blotchy deposits ≠ toning; the actual toning on this coin emerged from cleaning surprisingly intact.

Edited February 7, 2023 by Phil Davis

[kirispupis]

22 minutes ago, Phil Davis said:

To each their own, obviously, but I strongly disagree. I try to think in terms of what the die-engraver might prefer to put in his portfolio for a job interview. From that perspective, the Lysimachos in particular turned out rather well. Ugly/blotchy deposits ≠ toning; the actual toning on this coin emerged from cleaning surprisingly intact.

This is from me mistaking the sliders. The Lysimachos is an improvement, though didn't use an ultrasonic cleaner. 

Among those that did use an ultrasonic:
- The Thasos stater IMHO looks worse
- The Alexander "Babylon" tet is a dramatic improvement

[Furryfrog02]

I've heard mixed results with ultra sonic cleaners. 
Mostly to do with LRBs. Sure they shake off the looser dirt and crap but I've also read that they can shake off some of the flakier patina. 

I am looking forward to seeing your results though. Good luck.

[sand]

Here's a previous thread, about ultrasonic cleaners, for removing bronze disease. In one of my posts in that thread, I posted 3 Youtube videos, in which people tried ultrasonic cleaners. The Youtube videos caused me to decide, not to try an ultrasonic cleaner, at least not a cheap one. And, I wouldn't want to buy an expensive one. If there was any effect, it may have been a result of the water, or the solvents in the water, rather than the ultrasonic cleaner. However, it was only 3 Youtube videos, which is too small a sample size, to draw any scientific conclusions. But, 3 Youtube videos, was all I had time to view. It would be interesting, to see your results, if you try it.

 

Edited February 7, 2023 by sand

[Kaleun96]

12 hours ago, kirispupis said:

This is from me mistaking the sliders. The Lysimachos is an improvement, though didn't use an ultrasonic cleaner. 

Among those that did use an ultrasonic:
- The Thasos stater IMHO looks worse
- The Alexander "Babylon" tet is a dramatic improvement

I wonder what you thought I had done to the Lysimachos originally 😆

The Thasos is a bit of a weird one for me. I like how it turned out, though I have the benefit of having seen it in-hand originally and again now that it has toned nicely, but it was a frustrating one to clean. Learnt a lot from it at least and I think for some people they would prefer it as it is now than before, or it might just be me!

edit: here's the Thasos now. Not a big fan of the dull-ish gold toning personally but I'll take it over having no toning.

The Alexander tet I learned a lot from too. It's really the only coin I've seen where horn silver has destabilised the structure of the surface significantly. It's visible particularly on the edges where it was so porous that some surface has probably flaked off with the horn silver. I never did see any tiny specks of silver in the ultrasonic bath though, just the "dirt cloud" that you can see in the video. So still a bit of a mystery what was going on there but now I'm more careful with coins with porous surfaces, not only because they can be structurally weaker but also because shaking everything loose out of the pores can make the surface appear rougher than it did before.

Edited February 7, 2023 by Kaleun96

[Kaleun96]

In general, I was in two-minds about making that "cleaning" page. One reason is that I didn't want to encourage people to clean coins willy-nilly without being fully aware of the considerations I took into account before cleaning those coins or the coins I didn't clean, as well as the precautions I took. Second, because photos can be very misleading.  Maybe the surface appears brighter, or rougher, or more scratched, without anything having been done to the coin simply because I angled the light or coin differently. I also find a lot of scratches or porous surfaces can be hidden beneath deposits. I've had one person claim that ammonium thiosulfate has eaten away at some of my coins because they thought horn silver was something that just sits on top of a coin, not something that is produced from a corrosive reaction of the coin itself. I always use a loupe and also take these high resolution photos not only to document the change but also so I can study what has worked and what hasn't, or what potentially might be damaging the coin.

But since there's virtually no one else doing comparisons at this level of photographic detail, I'm willing to take some flak from those who might disagree on some of them or, in the case of the thiosulfate-eating-my-coin person, deal with some of the trolls 😄 Whether someone likes the end result or not, I think the comparisons are useful for everyone as it's so rare to be able to study some of the minute differences, or the appearance of some deposits at high resolution.

I'm honestly sceptical of a lot of before/after cleaning examples out there that use metal instruments (scalpels, diamond-tipped tools, dremel wire brushes, etc) because there's no way to tell from these photos whether the tools have done some "microscopic" damage to the surface that isn't easily visible in a regular photo. So I think these comparisons on my site show that a picture taken with your phone is not really sufficient to properly assess a before/after cleaning job, any minute scratches or roughness that appear after cleaning are going to be way too small to see without a good loupe or high resolution macro image.

So before cleaning, and in particular using an ultrasonic cleaner, make sure you have a good way of assessing the progress of the cleaning. If you're not able to tell whether you've scratched the surfaces by rubbing loosened deposits into the surface with a toothpick, or by using something that is more abrasive than you thought (toothpaste, baking soda), then I wouldn't recommend cleaning your coins as you may be damaging them without realising it.

[ambr0zie]

The extraordinary machine arrived today.

Although it was extremely cheap (lesson learned) - those money would have been spent in a much better way by flushing them down the toilet.

It arrived broken into pieces and with a hole in the "sink" because of a broken screw that took with it a large chunk of plastic. I managed to "repair it". And to my surprise it even  started to do its thing when I inserted the batteries!

Tested it with 2 modern coins (slightly dirty). Used tap water, distilled water, with/without liquid soap. Zero results.

Tested with my silver ear ring, that got quite black - 0.01% results (but not sure it is not wishful thinking).

I think a more serious machine, like the one owned by @Kaleun96 would do something. This one - just a toy.

[sand]

1 hour ago, ambr0zie said:

The extraordinary machine arrived today.

Although it was extremely cheap (lesson learned) - those money would have been spent in a much better way by flushing them down the toilet.

It arrived broken into pieces and with a hole in the "sink" because of a broken screw that took with it a large chunk of plastic. I managed to "repair it". And to my surprise it even  started to do its thing when I inserted the batteries!

Tested it with 2 modern coins (slightly dirty). Used tap water, distilled water, with/without liquid soap. Zero results.

Tested with my silver ear ring, that got quite black - 0.01% results (but not sure it is not wishful thinking).

I think a more serious machine, like the one owned by @Kaleun96 would do something. This one - just a toy.

Thanks @ambr0zie for providing another data point.

I wonder, if a water pick, using distilled water, and using the narrowest fastest-jet attachment, would have any effect on loose dirt, or bronze disease, or deposits, etc.

Edited February 8, 2023 by sand

[ambr0zie]

Note - I am not stating a positive or negative opinion about ultrasonic method. 

I am just stating and warning anyone - do NOT buy the cheapest ultrasonic cleaner on the market. I strongly suspect my device is just a plastic vase with a motor inside and nothing more.