Water damaged / rusted Morgans (how to restore)

Ultrasonic cleaners have a transducer that vibrates at a frequency usually at 25K - 40K times per second. Some of the fancier cleaners have a sweep frequency which will 'sweep' across these frequencies. The ultrasonic energy produces microscopic bubbles which act to loosen and scrub debris from objects.

I would, as jeffB said take care to suspend the coins in the solution as they will vibrate agaist the bottom of the cleaner tank.

Looks to me like it did a decent job of removing the crud, though. Worth a try IMO.

 

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That's what I'm thinking. The coin would be sliding around in the basket. That can't be good.

I agree. The coin needs to be suspended in some way. Maybe the gasket from an NGC slab could be used to suspend the coin away from the basket.
I'm not a fan of anything that comes in contact with the surfaces.

With the Morgans in this thread, I would try a bath in water first and acetone second. Next, I would go with Jim's thought of 1 part dip to 10 parts water for only a few seconds at a time. Watch for changes in luster and stop before you kill it. Some spots may not come off. You may have to live with some spots to save luster.

 

I understand that you believe this.

Think about a "soft enough" plastic. Heck, think about using your fingers to hold a coin. You advocate that, right? By the edge, wash your hands first, etc?

Now picture holding the coin that same way and dipping it into an ultrasound bath. Where does the rubbing happen? Do you think that the bath will jiggle the coin in such a way that it rubs against your skin? I don't; I think the coin and your skin will vibrate, but there won't be motion between the coin and your skin.

Now, will the ultrasonic vibrations in the fluid itself cause damage to the coin's surface, independent of any "rubbing"? That, I don't know.

 

I use this that works very well. It's a NON-gritty paste that you can rub in and also use with a Q-tip. It will NOT scratch your coin. Works amazingly well. Once it's clean, wash it in distilled water, then dry with a fiberless cloth.

 

NO NO NO NO NO

Any new collectors reading this thread. DO NOT follow this advice.

Polishing compounds have fine abrasives. Rubbing anything on a coin will damage the finish. It may not matter if it's something like a melt value 90% silver coin but it will be noticeable on an unc or proof piece

 

I hope nobody tries this. It will destroy any value the coin may have.

 

Good on @Oldhoopster for replying while I was still trying to gather my composure. (Edit: @ldhair, too.)

If you think this compound isn't damaging your coins, you don't know how to recognize damage.

 

Interesting tread and not to sidebar anything but I've given a lot of thought to trying the same things mentioned here. Is this the kind of damage a TPG would "fix" when doing coin conservation?

 

No. Damage can not be fixed. The coin will always be damaged.

 

Try the polishing compound on the bathroom mirror and see if it scratches. The hardness of glass is about 100 times that of gold, silver or copper. You may not see the scratches, but if it polishes ( removes surface) automotive metal it will do damage to coin metal.

When I first started in the last century, an old pro told me to use Ajax cleanser, and my very first morgan was damaged. Old numismatic 'magic' formulas still pop up.

Jim

 

The problem is, different materials resonate at different frequencies. The resonating frequency of plastic will be quite different than metal. So yes, the two things will absolutely be rubbing against each other, because they are resonating differently. This is why you can burst a crystal glass with sound, but the rest of the room doesn't explode.

 

I think you're off-base here. Yes, different materials resonate at different frequencies, but:

1) The whole system is being driven by a fixed-frequency oscillator (the ultrasonic transducer. I don't think there's an easy/efficient way to convert that energy into non-harmonically-related different frequencies; it would alternate between reinforcing and interfering with those other resonant frequencies.

2) Soft plastic will dissipate energy rather than building up a resonance (unless it's under tension like a gut guitar string; even then it'll dissipate energy, but can still build up a good vibration).

3) A frame firmly holding a coin will form a compound system with its own set of resonances, but there won't be friction between the two. There may be antinodes where they make contact, but even if there are nodes there, the objects will move together. (If this weren't the case, pianos and guitars would wear through their strings quickly at the bridges.)

 

Aluminum oxide is an abrasive.
https://www.meguiars.com/sites/default/files/pdf/MC204 SDS.pdf

 

True. They make sandpaper and grinding wheels with it as well.

 

I did an Internet search on "non-acidic rust remover" and came up with one possibility.
https://daubertcromwell.com/products/rust-removing-liquids/evapo-rust-de-rusting-solution/
I can't recommend it because I just don't know but it sounds good.

 

Interesting. I'm definitely not trying the same method on each Morgan. I want to see how each works and compare the results. I will *not* intentionally be using abrasive compounds though, as I believe the effects of each can easily be documented with other cull coins.

For the next dollar, I've started soaking this 1886-O in distilled water, in a slipped ceramic bowl. Hopefully, there's nothing for the rust to interact with, and I'll try letting it soak for 48 hours.



One important note on my previous method; i changed the water in the ultrasonic cleaner after 180 seconds (dumping a lot of blackish gunk on the first two cycles). I also added an ice cube after each 480 second cycle, as the water was getting noticeably warm from the vibration and I figured heat would accelerate any negative reactions.

 

Before I try an acetone soak, how do I neutralize acetone after taking the coin out? Does it evaporate away under room temperature? Or should I thoroughly soak the coin in distilled water to neutralize the chemical?

Found this on a quick Google search, and both methods seem to have their proponents:

http://www.ybw.com/forums/showthread.php?120800-How-do-you-neutralise-acetone

 

You don't need to neutralize acetone and the coin will dry in seconds.

 

As I understand it, pure acetone (not nail polish) will leave NO residue so a distilled water rinse is not necessary.
BTW use a ceramic/glass bowl.
I think acetone may dissolve plastics which would contaminate the soak.