Now that I've cleaned about a thousand of these things I have a fairly set cleaning methodology. Other opinions may be found in the links at the bottom of the page.
Me, I use the following methods;
Step 1) Basic Cleaning - Clean Your Coins Like You Clean Yourself (soap, water and a toothbrush).
You might be surprised at how many of these coins clean up with a simple soapy scrub. Do this first. Separate the coins you are happy with and with the rest move on to step 2.
Step 2) Standard Cleaning Methods
Option A) Olive Oil - Its Not Just for Eating Anymore.
This is the step which will test your patience. Put the coins in a small container and cover with olive oil. It takes a long time for this stuff to work. A few weeks will get rid of light dirt. Six months will begin to eat into the harder dirt. You can tell that the oil is achieving something when the oil begins to turn from green to blue (from the copper oxides). I've yet to see olive oil budge really packed dirt and encrustations. I give the oil about six months, with bi-monthly oil changes and coin scrubs with a toothbrush. I'd like to claim that I give the coins six months in the oil thanks to my enormous patience. Actually, it is due to my enormous backlog of coins waiting to be cleaned.
Option B) Distilled Water - Less Taste, Not Filling
This method was brought to my attention my Michael Moriarty via the Uncleaned Coins Yahoo email group. (If you haven't joined - do). Michael uses frequent changes of distilled water to draw the dirt and encrustation off of the coin, the theory being that the mineral-hungry distilled water breaks the bond between the dirt and the coin. I've tried it and it works. But be prepared to change the water every day, preferably scrubbing the coins between changes. Once the water has adsorbed its capacity for crud, further soaking achieves nothing. I have too many separate lots to work this way so I stick to olive oil. But distilled water has become the soak of choice for most of the coin-scrubbers I know.
Step 3) Scopeing Out the Situation
I've purchased a stereo microscope on eBay. They aren't nearly as expensive as I expected, about $200. With the microscope and small tools (needles and scalpels) you can remove dirt from between letters and around figures. I've plucked encrustation from Aurelian's ear and dirt from the crotch of Genius. A good oil soak and a few hours under the scope usually cleans up over half the coins. The rest are subject to;
Step 4) Electrolysis - The Final Solution.
If you have $15 for components and twenty minutes to spare you can remove everything that isn't coin. And this is where the controversy starts, because everything includes the patina. The patina on an ancient coin is like virginity. Remove it and you can't get it back. And it is just about as highly prized by many collectors. And to continue a bad analogy, I don't completely understand the value of either...
A patina gives a coin a nice color and indicates great age. Coins with even, thin patinas I leave intact. But many coins in the uncleaned lots I get have patinas so thick they obscure the legends and portrait details. Other coins arrive so heavily incrusted that I don't believe any amount of oil soak will loosen the concrete-hard crust. I know of one very experienced collector who in desperation wacked an encrusted coin with a hammer. (Worked, too.)
Step 5) Nic-a-Lene - Removes Deposits Faster than a Bank Failure.
Nic-a-Lene is simply dilute phosphoric acid and detergent. Electrolysis doesn't remove the dirt and patina evenly and you can ruin a coin trying to zap every last bit of grunge off. I use Nic-a-Lene to remove small areas of packed-on crud and the remains of the patina. When a few drops of this solution are put on a coin, the foreign matter immediately begins to bubble. I then begin rubbing the deposits with a Nic-a-brush. These are really fine bristled brass brushes which don't scratch the coin. The deposit is quickly reduced. Scrub with a toothbrush and rinse. Repeat until happy. Nic-a-lene and Nic-a-Brush are available from Stanton Coin.
Step 6) Regaining Tone
Nothing I know can replace a coins patina. Yet ancient coins shouldn't be new-penny shiny. Most often I try to return a bit of tone to the coins I electrocute with Deller's Darkener, available at Stanton. Deller's is a sulfur compound in a petroleum jelly type base. I apply a little to a coin and rub it in with a toothbrush. I then immediately wax the coin, let it dry and buff. A final step sometimes is to use a pencil eraser to bring out the highlights of the coin. The process looks like;
After Electrolysis After Dells After Erasing
I am also experimenting with other methods. If you are interested in the repatination of bronze, check out this site. There I discovered JAX. JAX is a neat solution used by professional sculptors to patinate their work. It comes in several different colors and I am still playing around with it, as well with several other methods. Below is a little demo;
Stripped of patina
Dellers JAX Gunmetal Bluing
And what did I choose? A combination of the above. The final result is below;
Barry and Darling Cleaning Suggestions
Hutto's Cleaning Instructions
Enchanted Treasures - The Cleaning, Restoration, and Preservation of Ancient Bronze Coins and Artifacts
Bill Gallagher's Excellent Electrolysis Page
Jim Vokes's Electrolysis Procedure
Bob Zito's Method
Jesse's Metal Detector Page
Dig the Bible - Restoration Page
November 26, 2001