Acetone Crisis
XpipedreamR
Posts: 8,059 ✭✭
OK, I have a coin. It's a proof. It was in a PVC holder, so I was advised to give it a cleaning in acetone, which I did, moving it through several glass dishes of fresh acetone. I noticed that it's got a slight "greasy" haze on the mirrored fields of the coin when I took it out. The acetone, while essentially pure, has some trace amount of oily organic contaminants in it (I put a few drops on a very clear, clean piece of glass, and can see the trace residue on the glass when it dries, so I can tell it's not something that was on the coin before).
I swish the coin around in a dish of water with dishwashing soap a few times, and the oiliness seems to be clinging to the surface. I rinse it off with rubbing alcohol, and while in the alcohol, the surfaces of the coin are nice and clear, but as it dries, there are some residual traces. The coin is now sitting in a dish of rubbing alcohol.
Recommendations?
I swish the coin around in a dish of water with dishwashing soap a few times, and the oiliness seems to be clinging to the surface. I rinse it off with rubbing alcohol, and while in the alcohol, the surfaces of the coin are nice and clear, but as it dries, there are some residual traces. The coin is now sitting in a dish of rubbing alcohol.
Recommendations?
0
Comments
You need more chemicals
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since 8/1/6
Joe
XpipedreamR, one of the more experienced members of the forum PMd me with a recommendation for something called "Coincare" to clean coins. Haven't used it yet, but other forum members may share their experiences.
Also, there's something else called "Uni-Solvent" that a dealer told me was good at removing PVC without residue. Again, I have no experience with it, but other members may.
<< <i>I have to agree with JLW-collectors who don't mess with chemicals don't end up with chemical messes!
This is a case where it is necessary. If you do nothing, and let the PVC continue to do its dirty work, this is what you end up with:
Me too. I bought one that said 100% pure -- haven't had any problems. Then again I've never used it on a proof coin, only MS coins to help remove thin films of oil/grime. So as Bfan says, if we were to use, say, Home Depot acetone on proofs, perhaps the mirrored fields would show residue after it dried.
Let's see...Now I can obsess about removing dust particles before I put it in an AirTite holder!
As for your oil problem, first I would have suggested not cleaning your coins at all, but since it's too late now, maybe you should try washing the coin with a very nonpolar solvent like hexane or ether. Whatever is on the coin is obviously not coming off with your more polar solvents...
For general reference, here's a list of some common solvents in order from most to least polar:
water
methanol (methyl alcohol)
ethanol (ethyl alcohol)
acetone
tetrahydrofuran
ethyl acetate
diethyl ether (commonly known as ether)
hexane
pentane
If something doesn't dissolve in a polar solvent, try one of its nonpolar buddies! (and vice versa)
A few caveats:
- First and foremost, I would suggest leaving your coins as they are and not treating them with solvents.
- If you absolutely must wash them, stick to solvents on the list above. Chlorinated solvents (dichloromethane, chloroform) have the potential to do a lot of damage.
Has anyone ever tried sonicating a coin to remove dirt/oil? It probably wouldn't do anything for the oil, but it might be a safe way to knock off those chunks of dirt that surround the devices. I'm interested to hear if anyone has any experience with this. If not, I'll bring some dirty coins into lab and give it a shot and let you know the results.
I have no experience in cleaning coins with ms70 or anything else, but in my 25 plus years as a hands on chemist I have used thousands of gallons of acetone and other common solvents. You can pay yer money and take your chances. If it was me I would buy the best stuff I could find like the HPLC grade. You know that that stuff has been freshly distilled and immediately packaged into CLEAN glass bottles.
Where does xylene (xylol) fall in that list? I've noticed with a few coins that xylene dissolved the foreign residue whereas acetone did not do so quite as readily.
As to haze on a proof (modern), I've removed said haze with the diluted thiroeau as K6AZ mentioned. For the chemists, what is the likely compound causing haze?
<< <i>Has anyone ever tried sonicating a coin to remove dirt/oil? >>
As in an ultrasonic bath? I've often thought of trying this to clean the compacted grit, etc. you often see around the legend lettering on something like a VF-XF late date large cent. Would it be safe to use acetone or xylol in an ultrasonic bath? Precautions? . . . other than ventilation. Could the on/off switch ignite the stuff?
If anyone tries an ultrasonic experiment please post a new thread on the results! That would probably be of great interest
to many of us here.
Great transactions with oih82w8, JasonGaming, Moose1913.
President, Racine Numismatic Society 2013-2014; Variety Resource Dimes; See 6/8/12 CDN for my article on Winged Liberty Dimes; Ebay
as far as the haze it might be do to some contaminant from the air reacting with the surface atoms
<< <i>Has anyone ever tried sonicating a coin to remove dirt/oil? >>
<< <i>If anyone tries an ultrasonic experiment please post a new thread on the results! >>
I had a friend try this for me once (he had one that he used at work). Another friend had picked up a few lots at a local auction and was surprised to find a bag of "Ancient Roman Coins". At least that what the outside of the bag was labeled as. Problem was, the only thing that we could determine was that they may actually be coins. So, we took one, tried acetone, nothing doing. I forget the other chemicals that we tried to use, but they all had little impact as well. Next, tried the ultrasonic bath. It did help, but not enough. Last step, we took a dremel to it.