Cleaning / Conservation: A Serious Discussion

Ultimately, most important determinant on a PARTICULAR coin is the condition of it. The next most important determinant is eye appeal. We have all met coins with problems, and have considered what can be done to improve the appearance.

Sometimes the consideration is in cleaning it.

Mostly, and quite correctly, you do not clean coins, because cleaning in almost all cases it will detract from eye appeal, not add to it. But there are exceptions. I have a rather nice silver tetradrachm of Ptolemy X11 of ancient Egypt. When I first saw this coin, it was so badly encrusted that there was doubt that it was even a coin. What's more, most of the scunge could not be removed mechanically (physically brushed off).

You might eye appeal was rated at zero.

A very great risk was taken. The risk was justified, because the coin was a 'write off' otherwise.

The coin was put in a bath of dilute acid. Dilute acid was used so that the rate of reaction could be controlled. Almost all of the inorganic scunge was removed, and the coin was revealed to be that as attributed above. Condition good VF. A very tiny amount of scunge was left to give coin eye appeal.

The value of the coin before the abuse? Perhaps $30. after? Maybe $150.

In 40 years of numismatics, it is the only coin I have cleaned.


Generally speaking, most ancients that have been interred in the ground will need some sort of treatment. Soaking in olive oil for months seems to be the most popular method of treatment.

Acetone is a favourite for modern coins, but good old soap and water works wonders for gold coins in EF or less condition.

I wish I had the time to treat this subject more thoughtfully but right now my mind is going in like eight different directions at once and I have to go. I'll say this much, though. Good question. We do this right, pool together our knowledge and experience on this subject, and we all stand to gain.

I thought I'd add to this since it's kind of gone stagnant. I admit I have used these processes but not for anything nefarious, stupid or to try and trick anyone.

Cleaning a harshly encrusted coin is never anyone's idea of a good time but there are times when if all else fails....

Before the advent of the handheld Dremel like tools, I bought and used air powered dental tools for these jobs. I would take a badly encrusted coin (or piece of jewelry, often it was silver jewelry) and basically polish or whiz the surfaces free of the main crap using a touch as light as possible. I would make up polishing heads from layers of cotton cloth infused with hide glue and mixed with 800 grit aluminum oxide. Aluminum oxide was used because it has a low fracture point so it continually fractures and resharpens itself. I typically used mineral oil for lubricant ... lots of oil. I put my new polishing heads in a 5 ton press to finish and soften them before use. After working on the coin it looked whizzed when I was done with it, anyone could see the surface lines and total lack of any lustre. It's worth pointing out that a coin this badly beaten was often pitted, but not always.

Once the coin or jewelry was cleaned of major debris, I'd move it to a modified rock tumbler. The tumbler drum was steel and inside was cemented vulcanized rubber from the side of a 10 ply truck tire. So in the coin or chain would go, half filled with a mix of 6000-8000 grit polishing compound (what they used for polishing platinum jewelry)and oil. Depending on the coin material it could be in as little as an hour or as long as six or even a day - even longer if you had a rough touch with the dental tool. A bath of soap and water using a silk cloth would remove everything at this point. The hairlines would be gone, the coin would be a super ugly chunk of metal that shone like the sun with absolutely no lustre or redeeming qualities. You could add some circulation marks by rolling in a bag of pennies for a while.

The best way to bring it back to some semblance of normality would be to place it in a glass sealer on a bed of oak shavings and leave it in the sun. Worked miracles for copper cents and silver coins. Patina reformed in no time. Nickle, not so much. It would take on a sickly yellow appearance, was better to just leave those in the window sill.

Voila, you went from a hunk of crap twice the thickness of a normal coin to something that reasonably looked like sort of like normally circulated coin. These often got made into jewelry or art of some kind.

Why? Sometimes sheer boredom and sometimes a desire to see and display what you found. I still have a few samples of these pennies with a deep chocolate brown very natural toning I was using to make cupboard door closers and a pair of earrings I made the better half from some Victoria dimes I found encrusted with asphalt a long time ago. I made a childs bracelet out of restored fishscales we found in a jar of mixed coins at an old burned out farmstead using this method as well.

As to Carl's comments, you're talking about coins, once these are altered they just take on the term artifact or found item in my mind. We all buy coins and that's fine. That's not what the discussion is here, these found items just happened to be coins once. They can be used, displayed and enjoyed for other reasons that are valid. Sometimes the tale of the found dimes being earrings over a beer is good enough to make it worthwhile.

Here's a scenario that just came up for me.

I bought an MS Red Brown 1916 Lincoln on ebay. Got what I thought was a great deal on it - $15.50. Came yesterday and it is even better than the pictures - beautiful red brown color, nice original surfaces - just great. BUT - under the 10x loop and small bit of what looks like verdigris on the reverse at about 6:00. Oh. Hmm - what to do - send it back? It's an awesome coin, don't really want to do that. So, I'm going to pull out the Verdi-Care this weekend and do a little spot treatment. It's worth it to me to prevent any further spread on what is a really nice coin. Call it cleaning or conservation I am not sure, but it does seem like a rescue mission to delay or prevent a threat that could ruin a nice coin if left unchecked.

I think that is an acceptable risk to take in my opinion.