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Coin Cleaning

see also:
Coin Cleaning

Cleaning bronze and Romana
Cleaning Copper
Advanced Cleaning

New Hope For Those Hopeless Coins

One of the most oft-asked questions by detectorists is, "How do I clean the coins and tokens I find? Sometimes I donít know which question is asked most: "How do I clean my coins?" or "What do women really want?" Iíve been married for more than 10 years, grew up in a household of sisters and dated women extensively for an extended period of time, so naturally, I know more about cleaning coins.

The best way to clean coins without damaging their value is, of course, to have them cleaned by a professional coin dealer. If you even think a coin or token might have any kind of value whatsoever, have it evaluated. In some cases, even rubbing a coin lightly under running water can mar the surface with tiny scratches. There are some detectorists who say there are ways to home-clean coins and have the evidence escape a professional coin dealer, but itís hard to fool a truly professional numismatist. And there are some coin dealers you just donít want to try to fool -- especially in my neighborhood, where coin dealers have names like Maury The Fist. But the vast majority of dug coins are worth only face value or less due to wear from circulation, lack of rarity or environmental damage from moldering in the ground for so long or being exposed to fertilizers, so they arenít worth the professional cleaning expense. Still, you might want to clean them up enough to at least read them for display or adding to your collection, so the devaluation caused by anything you could do at home would be no huge deal.

Iíve seen a lot of different home cleaning methods, from using a steel brush to soaking coins in lemon juice. One of the gentlest methods is to soak your finds in olive oil. You simply immerse the coins in plain old olive oil (change the oil when it gets grungy-looking) until the crud works itself loose. This can take anywhere from several days to several months, depending on how crusty your find is. Not everyone has this kind of time, but if you do (especially if you want to preserve the fine green patina on copper objects and donít mind yet another thing on a shelf catching dust), the olive oil soak is the only ticket.

Another method I've seen is by building a home-made electrolysis machine. This involves jerry-rigging an AC adapter for a small electrical appliance (like a cassette tape player) by slicing off the end that's plugged into the appliance and attaching alligator clips. One clip is attached to the object to be cleaned, the other to a stainless steel spoon or large bolt and dumped into a glass container containing a salt water or baking soda and water solution. The adapter is then plugged into the wall. Cleaning time varies depending on the mA rating of the adapter.

Electrolysis is ideal for anything metallic, including iron objects. I've tried this home electrolysis method and sometimes it works well and sometimes it doesn't. I don't recommend it, tho, because the adapter tends to heat up quickly, and you can't leave it unattended for a single minute because of the very real danger of the adapter starting on fire. Plus, I'm one of those hardware-inept guys who can slice off a finger using a screwdriver, so electricity and I don't mix well. Especially when it involves using electrical accessories in ways that weren't originally intended.

So is there an undisputed best way to clean coins, especially if you donít want to undertake the numismatic version of watching paint dry by using the olive oil soak? I thought Iíd ask the folks who ought to know: The American Numismatic Association, which is this countryís foremost authority on identifying and conserving coins and exonumia. It seemed to me that asking the ANA the best way to clean coins would be like asking paleontologists at Chicagoís Field Museum the best way to dig up dinosaur bones. According to ANA Museum curator Robert W. Hoge, there is no best way. There is no "ANA endorsed method for cleaning undertaken by non-professional conservators," Hoge wrote in a reply to my e-mail, "except perhaps to recommend repeated baths in changes of distilled water, with a final thorough and quick drying with an oven or hair dryer."

He added, "You might check with museums in your area to see what they do for conservation needs" and signed off with a "Good luck." Uh-huh, sure. The closest thing to a coin conservator in my area is Maury The Fist, and heís a bigger authority on burying things, not digging them up.

Seeing that Americaís foremost coin conservators donít have an official prescription to keep us from ruining our coins, Iíll pass on the method Iíve been using on my more notable coins with astounding success Ė even for the nightmarish baked-on caked-on corrosion Ė with no apparent damage to the coin whatsoever. Best of all, it works in under a half hour. Itís a method I found posted last September to the Findís Relic Hunting Forum by someone in Florida who posts by the name of The Mayor.

One of the main ingredients of A&H Super Washing Soda is sodium carbonate, which is two extra sodium molecules and a missing hydrogen molecule away from being sodium bicarbonate (better known as baking soda), except itís too busy spending its time being soap. This method works through some "Beakmanís World" home game version of chemical electrolysis brought on by the interaction of the aluminum foil with the sodium carbonate and other assorted A&H-manufactured mystery guest chemical ingredients.

First, a word on what this cleaning method will and wonít do. First, it doesnít work on anything iron. It does work like a charm on anything brass, copper, silver and old nickel (V nickles supposedly clean up nicely using this method, but I havenít found any to find out for myself). Best of all, it causes no pitting unless the coin was pitted to begin with. Because this cleaning method removes all corrosion, it will strip off any pleasant, attractive green patina from copper objects. Patina is, after all, a form of corrosion, so if you want to retain any of it, use the olive oil soak. This method does not work well on modern nickels and clads, and it doesnít work at all on zinc pennies -- which doesnít matter anyhow, since cleaning clads this way is a waste of time and washing soda because nobody displays clads. The only fitting thing to do with clads is to roll Ďem through a coin tumbler for spending.


Youíll need:

1) A shallow glass dish, like a casserole dish, or glass jar. For a few coins or small objects, I use a small Ball, Mason or mayonnaise jar.

2) A piece of aluminum foil large enough to fit in the bottom of the glass container.

3) One box of Arm and Hammer Super Washing Soda. Not baking soda, but washing soda. Itís found in the detergent section of most large grocery stores. Nothing else will work except A&H washing soda.

Fill the glass container with HOT water. I find the best results always happen when I put the container in the microwave and get the water boiling. If you just run real hot water out of the faucet, the cleaning method doesnít work as well.

Take the piece of aluminum and use your finger to smooth flat any raised wrinkles. If a coin sits on a raised wrinkle during the cleaning process, it will create a dark spot on the coin. (If this does happen, the spot can be removed with another cleaning.)

Put the aluminum in the bottom of the container. (Use something like a pencil to push the foil down if the waterís been microwaved to boiling.)

Drop in the coin to be cleaned. If youíre cleaning more than one coin, donít let them touch each other. For best results, donít mix metals. Clean silver with silver, copper with copper and brass with brass.

Dump in two or three heaping tablespoons (depending on how much gunk is on the object) of the washing soda into the water and stir. The washing soda doesnít need to be completely dissolved.

The whole works will start foaming and fizzing like grandmaís dentures in a glass on the nightstand. In a short time you will see the encrustation start to fall away and the water take on a funky gray-brown color. Let the whole project sit until the water has cooled to room temperature. Then pour out the water and retrieve the cleaned coin. In most cases, one time through this cleaning process will do it, but if the coin is still crusty, repeat the process as many times as necessary. You wonít hurt the coin by cleaning it repeatedly this way. Another thing: If you have to clean the coin more than once, put in a new sheet of tin foil. The process, youíll find when youíre finished, causes the foil to begin dissolving around the edges.

Once your coins are cleaned to your satisfaction, place them in a protective sleeve or collection album. Contact with the oils in your skin and the air will cause tarnishing.

This method worked great on the slightly gunky wheat pennies I dug up over the past year and the less than clean coins I have been picking out of pocket change over the years. But how about the numismatic equivalent of Momís worst laundry nightmare? I had just the tickets: three coins I dug up in a suburban Chicago forest preserve last summer. These were a heavily tarnished 1905-O Barber dime (center), and a 1976 Roosevelt dime (right) and a 1984 Canadian cent (left) which had been in the middle of what was once a burn pit. The dime and penny had been subjected to an excruciatingly hot fire -- hot enough to melt chunks of glass which had been lying next to the coins. The Roosevelt had been burned so badly, the metallic coating had bubbled up and away from its core.

As you can see by the "before" scans above, the penny and dime were cooked and corroded beyond recognition.

In this "after" scan, you can see what major miracles can be accomplished with the washing soda cleaning method. A single cleaning cycle cleaned the Barber quite nicely, and lifted enough crud from the Canadian and Roosevelt to at least identify them. A second cycle finished removing all of the corrosion from the Canadian and enough from the otherwise unsalvageable Roosevelt to make a few additional cleaning cycles worthwhile had this been a display-worthy coin.

© 1999 Scott Buckner

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