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More Advice on Coin Cleaning
mike thorneBy Mike Thorne, Coins Magazine
July 16, 2008
mike thorne

In my last column, I talked about coin cleaning with abrasive methods, which should almost never be employed, and with coin dips. If you follow the directions on the container, the acid-thiourea dip method will produce satisfactory results on high-grade coins, as long as you don't do it repeatedly on the same coin and you take care to neutralize the action of the solution.

I should note that you should never use this method on a copper/bronze coin, as the coin will turn a pink color that gives it a decidedly cleaned appearance. Also, keep in mind that this method involves the loss of some of the surface metal of the coin, which makes it "cleaning that is abrasive only some of the time," according to Scott Travers.

What about non-abrasive cleaning? According to Travers, such methods are "being recommended increasingly before long-term storage." That is, coins are inherently dirty, whether we realize it or not. Thus, before we commit a new coin in our collection to some form of encasement or housing, we need to "purify" the coin's surface as much as possible.

In an earlier column, I mentioned a customer who told me that he boiled all his coins before putting them in holders. Perhaps there was method to his madness after all.

For years, the non-abrasive method of choice was a chemical named trichlorotrifluoroethane (try saying that 10 times fast), which removed surface impurities without attacking the coin's surface. You couldn't use it to remove tarnish, but it would take off the PVC residue (green slime from storage in soft plastic holders), dust, grease (oils from your fingers), and tape residue.

Unfortunately, trichlorotrifluoroethane, sold under the brand name Dissolve, damages the ozone layer in the atmosphere, so it is banned by the government. (I still have a can of it, but I suspect I won't be using it anytime soon. My question is, how do I get rid of it in an environmentally safe manner?)

Fortunately, according to Travers, E&T Kointainer of Sydney, Ohio, the same company that made Dissolve, now offers a new product called Koinsolv for the same purpose for which Dissolve was employed. Given the lengthy list of exotic chemicals in Koinsolv, I wouldn't look for this to be a permanent solution to the nonabrasive cleaning problem.

You can also clean coins nonabrasively with an ultrasonic cleaner. As J.P. Martin writes, "Ultrasonic cleaners with distilled water and a little detergent can be used to remove heavily encrusted dirt from a coin, as well as coral encrustations from sea-salvaged coins. Used in connection with a dip they can be very effective in removing heavy tarnish but the reaction will take place faster than you think, so be very careful not to leave a coin in too long."

Of course, if you use the ultrasonic cleaner "in connection with a dip," then you're right back to an abrasive form of cleaning.

My only experience with ultrasonic cleaning was somewhat negative. Back in the early days of certification, I had a Good-6 1913-S Barber quarter that I wanted to have certified. The only service available at the time was the American Numismatic Association Certification Service, and it was strictly geared toward authentication, not grading.

I sent in my coin and got a note back telling me it had some crud around the mintmark and asking me for permission to clean the coin ultrasonically so that they could inspect the mintmark area. I gave my permission, the coin was ultrasonically cleaned, and they decided it was genuine.

Unfortunately, I never liked the coin as much after the cleaning as I had liked it before. Before the cleaning, the coin had a completely natural appearance. In other words, it looked just like it should have looked as a well-circulated Barber quarter. Afterward, the coin didn't look shiny or harshly cleaned, it just had a slightly unnatural appearance.

I guess I thought it looked "too clean" for its low grade. I kept it awhile but eventually sold it along with the rest of my Barber quarter set.

Martin also mentions using olive oil to clean copper or bronze coins. He doesn't specify the type of olive oil to use, so I would go with the cheapest variety available.

If you like for your cleaning action to occur immediately, you're going to be disappointed with the olive-oil method, as the instructions are to let the coin soak in the oil for at least 24 hours. After this, you wipe off the oil with a soft cloth, such as a cotton t-shirt. Martin notes that because of this light rubbing to get rid of the oil, you should not use this method on uncirculated or proof specimens, as hairlines will result.

Martin ends his article on coin cleaning with a brief paragraph on the "safest cleaner" of all, "plain old Ivory soap," which you apply "gently by hand" and rinse thoroughly in cold running water. I have no experience with this method.

Martin's final paragraph suggests that you apply any method you're interested in using on common coins first, so that you can see how to do it and what problems might occur. Actually, I've read this warning many times in articles on coin cleaning, and it makes perfectly good sense to do this, but somehow I never have. I guess I've always been in too big a hurry to apply the cleaning chemicals to the coin that I thought needed cleaning.

Finally, virtually everybody who's ever written anything about coin cleaning ends with the following admonition: If you have any doubt about either your ability to employ a cleaning method or the final effect it will have on a particular coin, then don't do it. Probably a hundred coins have been ruined for every coin that has been helped by cleaning, particularly if the cleaning is done by someone who's not extremely familiar with the technique and its likely results.

Next month, I'll discuss basic coin storage methods.

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On July 17, 2008 zimtran said

To remove toning from silver, a great method is:  Take a small pan.  Take a piece of aluminum foil and place it on the botton of the pan and fill the pan with water.  Put just a little baking sode in the pan.  Bring the water to a boil so the baking sode disolves. Let it cool.  Place the coing in the water in the pan so it is on top of the aluminum foil. bring the water to a boil again.  Let it cool again by pouring clear cold water in the pan until it's cool again.  Voila! Bright silver, toned aluminum foil.
On July 18, 2008 Gregory Kipp said
I find that acetone or rubbing alchol applied with a cotton swab works very well.  They can remove surface contamination without affecting the metal.  Let the coin soak for a short while to desolve more stubborn adhered material.  But they will not remove corrosion or toning and any scrubbing action can produce hairline scratches on the coin.  Acetone is the more powerful solvent, but it produces dangerous fumes, so work in a ventalated area.
On August 16, 2008 Koichi Ito said
Cleaning Coins must be last resort! Do not use cleaser like Comet or Ajax! Better use liquid detergent than solid to clean coins. You can soak coin into alcohol and wash with distilled water and wipe it dry! Best to clean it for last resort! Avoid cleaning  coins as much as you can!
On September 10, 2008 Ahmed Abbas Maswood said
Can somebody confirm whether dipping in alcohol is better than soaking in detergent ?
This is for surface contamination of ordinary coins.
What about silver coins ? How do jewellers polish them ? And more importantly, is it a good idea for long term storage of silver coins.

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