Does anybody have experience with cleaning ancient coins?

I've read quite a bit about cleaning ancients and it seems like a lengthy process. Luckily I'm patient and in no hurry. Anybody have any good resources or techniques they could share?
Thanks

 

Log in or Sign up to hide this ad.

There are a couple of methods to try. I've used a distilled water soak over a period of several days. After the soaking, I rinse them off under the tap and then use a toothbrush to remove loose dirt. After that, I apply a dental pick to remove encrustation gently.

Some folks recommend an olive oil bath for a period of several days to months to remove tougher encrustation/dirt. I've tried this method and after removing the coins from the olive oil I use the same toothbrush technique, followed by the dental pick. This works better than simple distilled water but be warned that the olive oil will impart a dark color to the coins. Not totally unappealing, but just something to keep in mind.

I've heard of boiling coins in olive oil (the so-called hot pot method) but have never tried it.

Another method is liquid descaler, which I would not recommend. I read about this method on the web, but after 24 hours in the descaler (which did remove the dirt) I found out that it removed patinas and in some cases with late roman bronze obliterated legends and reverses which just slid off the coins.

There are even more methods out there such as electrolysis but I have not tried those yet. These days, I'm pretty much not buying uncleans and I still have about 500 coins to clean up sitting in a mayonnaise jar.

Here's an example of a cleaned Arcadius which was basically a featureless slug before cleaning, but at least now can be attributed...

 

Thanks. I was thinking about trying this but I'm finding it difficult to find uncleaned coins to purchase. I don't trust the eBay ads, especially the ones based in Eastern Europe.

 

I've found out with uncleaneds that even with a few hidden gems (I once got a rare Macrianus antoninianus in VF condition in a hoard) that you get what you pay for. Lots and lots of coins that are either totally worn under the encrustration or are featureless slugs. So, even with some success in cleaning up ones that are OK you end up paying for a lot of coins that are basically worthless. Coupled with the fact that it seems to be getting harder and harder to find decent uncleaneds (see the other thread on the Forum today) then it is a bit challenging.

 

I’m treating only coins with spreading bronze disease. I soak them for two or three days in a mix of baking soda and washing soda solved in distilled water, then scrub softly with an electrical toothbrush. And repeat. Usually it works.

 

verdi-care and toothpick seems to work best for me.

 

I used to sell uncleaned coins many, many years ago. Here's a copy, edited slightly to remove all the out-of-date links, of the note that I used to include with the coins:

Cleaning Ancient Roman Coins

The first thing to do when you receive your coins is to brush them off with a nylon bristle brush. An old toothbrush works well. If you cut the bristles down to half their original length it works even better. Inspect the coins after brushing them to see if any of them are now clean enough to identify. Chances are most, if not all of them, won’t be, but sometimes you get lucky. Assuming that your coins still need additional cleaning, soak the coins in tap water for a few minutes and then take them out and scrub them with the brush and a little dishwashing liquid and then rinse them well.

Some coins may be identifiable that this point, but most coins will still require additional work. Although there are many different approaches that people take to cleaning ancient coins, I have had the most success with long-term soaks in distilled water. Distilled water is readily available at most supermarkets or department stores. It is better than tap water, spring water or bottled drinking water because the lack of minerals in it makes it draw out mineral build-up on the coins. It is cheap, and a gallon is enough to clean hundreds of coins. I usually let coins sit in a cup of distilled water for a week or so and then take them out, scrub them using dishwashing liquid, rinse them off and, if needed, put them back in a fresh batch of distilled water.

Patience is your most important ally in cleaning coins. Although some coins will clean up very nicely after one or two soaks, with others you may need to repeat this process for several months. I have heard of people who have taken as long as two years to clean a coin using this method, but they have been very satisfied with the results. Still, there are a few tricks that, if used carefully, can help speed up the cleaning process. One handy piece of equipment is a small brass bristle brush. You can usually find these at hardware stores for around $2.00. Check the patina (the outing coating of surface metal oxides that accumulate over the centuries) carefully before using brass or silver bristle brushes because some patinas are very soft and can be damaged. Never use a steel bristle brush on any coins—it will scratch them—and never use a brass bristle brush on silver coins, for the same reason. Another helpful technique is to design you own brass tools. Brass rods are usually available fairly cheaply from most hobby stores. It is easy to file the end of a brass rod into a point with a sharpening stone. It can then be used to pick dirt out from inside small crevices and between the letters of uncleaned coins. Brass tools can be especially helpful if you use them under magnification with a jeweler’s loupe or low powered stereomicroscope.

There are many other methods that hard-core uncleaned Roman coin cleaners (often called bottom-feeders) use. Cleaners are always experimenting with different liquids like WD-40, olive oil, Oxy-clean and Kaboom, but I’ve found repeated soaking in distilled water followed by scrubbing with dishwashing liquid the most effective.

Extremely stubborn or encrusted coins can sometimes be cleaned using electrolysis. If you use the terms “ancient coins electrolysis” to search the Internet you can find information about creating your own electrolysis setup.

 

Thanks for the info. Any tips on where to find decent uncleaned coins to try. This on? I've had no luck as I don't really want to go the eBay route.

 

It sounds rough, but before trying electrolysis, I’ve had some success laying coins in a blob of Elmer’s glue and then ripping it off. This only works for coins with hard mineral deposits. It won’t remove anything that electrolysis won’t, and I’ve actually managed to preserve fairly decent patinas this way, although it was slightly uneven. The only time it did real damage was when the coin turned out to be riddled with bronze disease. My experience is limited, but archaeologists do far worse things sometimes. That’s where I learned this. Before and after:

 

Check out nobleromancoins.com for their detailed cleaning guide.

When they have "premium uncleaned coins" they are really good.

John

 

Yeah, they have lots of 100 "premium" uncleaned coins for $135, which is a good price. Just checked out the website.

 

@Theodosius, do you have any experience, direct or indirect, with their coin cleaning service?

 

I have not paid them to clean anything for me, though I have been tempted at times. I think Kevin is a pretty good cleaner, certainly a lot better than me.

Read their cleaning guide to see what techniques they use.

 

The more expensive their cleaners the better the coins.

I would buy the most expensive cleaners they have because cleaning is a lot of work, you want to get something good out of it. I think their top coins are 3.95 or 5.95 each when they have them. I have gotten silvered ants from those lots.

 

I've heard this before. Actually, I think a hot glue gun works even better. But I haven't tried it so I can't vouch for the method.

 

I haven't dealt with nobleromancoins for years, but back in the day they were honest and had nice quality coins.

 

Hot glue works with a couple of warnings. Do not try it on a fourree as it will lift the plating. It is a mistake to remove the coin from the hot glue until it has cooled completely (10 minutes or so). This allows the glue to peel off in one piece rather than leaving residue on the surface in small pieces that can be hard to remove. Like all cleaning methods, glue only works on some kinds of dirt. The hard part of cleaning to me is deciding which method is best for which coin. I am not patient enough for this hobby. I prefer to allow those who have the experience to clean worthwhile coins. If what you want is a pile of ordinary, common coins, you can but them from people who cleaned them in hope of finding a rarity but have a thousand cleaned ones that are worth less than the uncleaned versions just like losing lottery tickets are worth less than ones this a one in a hundred million chance of being a winner.

 

I'll add my 2 sesterces worth. Using distilled water is good in theory, and if you are cleaning uncirculated or proof coins, invaluable. For most other uses, tap water is 99.99+% pure and works just fine. If you wish, by all means do the last soak/rinse in distilled water. Oil..ehh...if you want to use oil, penetrating oil or WD-40 seems a better choice to me. The goal of all this is to remove all the crud you can without inflicting damage on the coin or on any beautiful patina. A patina without being able to read or see the devices seems unproductive to me.

 

The rap against tap water is that in many localities--not all in Michigan--tap water contains traces of chlorine. Some coin cleaners have expressed concern that in these areas the combination of tap water and fresh coin surfaces might trigger bronze disease. Considering that distilled water (DW) is available in most grocery stores for around $1-2 gallon and that a gallon will usually last for several months, it seems like a small price to pay for the extra peace of mind. I will sometimes rinse a coin off with tap water, but for long-term soaks I use distilled.

I agree with your assessment of olive oil. When I first started cleaning coins, soaking in olive oil was the most commonly recommended method. So that's what I started off doing. Seemed to work okay on many coins, but I was curious why, after soaking for a week or so, the con turned black and the oil changed color from yellow-green to light blue. Turns out that olive oil is slightly acidic, and the blue color was from the copper that leached out from the coin. So when I heard someone suggest using distilled water, I gave it a try--much cheaper, less messy, less damage to the coin surface--and have used that ever since. If DW soaks didn't work, then it was time to escalate: brass bristle brushes, brass tools under a stereo microscope, or, in extreme, apparently hopeless cases, electrolysis.

If you do try soaking in other oils, your last step will be to remove the oil film from the coin surface. I remember several people recommending using tri-sodium phophate (TSP, available in most department store) to remove oil film, but by then I'd switched to DW, so I can't vouch for it.

Basically, there are two types of liquids, polar (electrically unbalanced) and non-polar (balanced). Polar liquids, like water, will dissolve polar deposits, non-polar liquids, like oils, will dissolve non-polar deposits. Soaps, like dish-washing liquid, help to break down non-polar deposits, so the combination of repeated DW soaks and gentle scrubbing with dish-washing liquid should break down both types of deposit. I don't know of anything that you can combine with oil to help it break down polar deposits--not saying there isn't, I just don't know of anything--so that's another reason to try DW soaks.

 

I thought dishwasher liquid contains acid, too.