RPSeitz's Blog

13 May 2019

Cleaning Ancient Coins

Ancient Coins | RPSeitz

An inexpensive way to purchase Ancient Coins is to purchase them unclean. This means to purchase them as they look immediately after they are literally dug out of the ground. These coins are often heavily encrusted and difficult to see. The coins in this condition must be cleaned in order to identify them.

Cleaning Ancient Coins is a very long process and requires a great deal of patience. The process I use begins with soaking my Unclean Ancient Coins in distilled water for a month. Each week I scrub the coins with a toothbrush and replace the distilled water with fresh distilled water. After a month, I look to identify each coin. If the coins are still too encrusted to identify, I then repeat the process just described for another month; scrubbing the coins weekly with a toothbrush and replacing with fresh distilled water. At the end of the second month, if I still cannot identify the coins, I repeat the process, except instead of distilled water, I soak the coins in Pure Olive Oil for a month; each week scrubbing the coins with a toothbrush and replacing the old Olive Oil with Fresh Olive Oil. If after another month I still cannot identify the coins, I use electrolysis.


Although all the experts advise against cleaning coins as it could seriously reduce their value, sometimes, at least with Ancient Coins, where there is really heavy encrustation, it is the only way to remove enough to reveal any detail. There are a number of acids and chemical preparations that can be used, but as I am not prepared to handle these corrosive substances and the results often strip off all the antiquity from the surface, electrolysis is my preferred method.

To start with you need an electrolysis unit. The cheapest way, providing you are reasonably confident, is to build your own using cables, alligator clips, a spoon, a paper clip, and a 9-volt battery. There are dozens of instructions on YouTube to help you, but basically, you cut 2 cables to 12-inch lengths, strip back about an inch of insulation from each end and attach crocodile clips to each end. All you then need is a plastic container, a 9-volt battery, a paper clip, a spoon, distilled water, and a suitable electrolyte and you are ready to go.

Fill the plastic container with distilled water and stir in a teaspoon of bicarbonate of soda until dissolved (you can use ordinary salt but with that, the process results in the release of chlorine gas which can be harmful if inhaled). Attach an old spoon to the positive wire and the coin to the negative wire and suspend both in the electrolyte making sure they cannot touch, and only then attach the other ends to the 9-volt battery. (If you are not sure which is which, simply dip both clips into the water, the one with the most bubbles rising from it is the negative). You can attach the coin directly to the crocodile clip but to prevent unnecessary damage I bend a paper clip into a cradle to support the coin and attach that to the crocodile clip.

I let the process work for about 10 minutes, switch off the power, remove the coin and brush it with a toothbrush to remove any loosened deposit then repeat the process until I have removed as much as possible. With most encrustation, it can take 20-30 minutes in total to achieve a satisfactory result.

The variables are the power of your battery, the strength of your electrolyte and the degree and type of encrustation. A kitchen timer makes sure I don't lose track of time! My greatest success was with 11 Roman coins (See pictures below) that were so badly encrusted that I thought they would never be clean enough to identify them. I put them through the process individually and in three sessions each, I managed to remove all the encrustation and reveal the details beneath. Please note that some coins may be in such poor condition that you could end up destroying them in the process rather than improving them, but that is the risk you have to be prepared to take. So far, that has not yet happened to me, but, a couple of the coins have a great deal of pitting on the surface, which is an indication that I ran the electrolysis too long. I hope this is helpful for those interested in Ancient Coins.



Level 5

Interesting... I have never heard most of this.... Thanks so much for the info! Cheers, NM


Level 6

Interesting information. I have heard of using the olive oil.


Level 4

I had always wondered how this was accomplished. Great blog. Thank you.


Level 6

I enjoyed this blog. I too have tried the olive oil method. Not that great success. next time, when I my bulk, dirty ancients, I will try your method. i agree with Pat but understand this is a craps shoot you play. I like the coin roll hunting analogy. Thank you.


Level 6

I am no expert, but heard one time about soaking coins in olive oil.


Level 4

Terrific blog. I am not a collector of Ancients, but I have read about the processes you describe. Ancients are the one type where cleaning is often a necessity.


Level 7

Your blog made me glad I didn't choose ancients. There cleaned by the professionals for a reason. It's done right. No scratches from tooth brush and always pat it dry. Distilled water is the only safe thing you use. Nothing else or send it in. Always S play it safe. Thanks Pat


Level 4

Pat, you are right. It is best to have Ancient Coins cleaned by professionals and therefore, you can and probably should purchase Ancient Coins from reputable dealers for the best grades and most collectible Ancient Coins. This is expensive but is the best route to go. I do this for my collection, but, if you want to have some fun, you can also purchase Unclean Ancient Coins and clean them by following the process and rules to see what you are able to find. This is the Ancient Coin equivalent to U.S. Coin Roll Hunting. The difference is you will not know what you have found unless you clean them.

I agree that it is always better too avoid cleaning coins, but when it is in such a condition where , like the ancient coins you described, needed to take the risk, then do it. Thank you for describing several good methods, it is great information


Level 4

Purchasing Unclean Ancient Coins and cleaning them by following the process and rules to see what you are able to find is the Ancient Coin equivalent to U.S. Coin Roll Hunting. The difference is you will not know what you have found unless you clean them.

It's Mokie

Level 6

Thank you for the valuable advice on cleaning encrusted coins, I just bought a metal detector so may end up needing to use your distilled water, or olive oil techniques myself.


Level 5

Thanks for the instructions. I did this a few times years ago and realized that I don't have the patience for it. Never tried the electrolysis method. I always had the most luck with olive oil.


Level 4

Electrolysis is always the very last resort for cleaning Ancient Coins. Ancient Coins definitely take a lot of patience. Ancient Coins operate under different rules. This should never be used on U.S. Coins it will most certainly hurt the value.

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