Cleaning ancient coins using electrolysis

A lot of people swear by electrolysis, others refuse to have anything to do with it. For myself, I've had pretty good results with it. The fact is that there is simply no layer of dirt that is so bad, that it cannot be removed using electrolysis. The only problem is that electrolysis does not only remove dirt but can also remove the patina. The reason is that electrolysis causes the top layer of molecules on the coin to microscopically vibrate, shaking off the dirt - and the patina if left in the electrolysis bath too long.
This page will explain how to build a diy electrolysis bath.

What do you need?

- An AC adapter (at least 300mA) e.g. an old battery charger
- 4 cable shoes (the type you press on)
- 4 clamps
- A stainless steel article, must be non-magnetic (e.g. a spoon)
- Washing soda (Sodium carbonate) or Salt (strong! use less!)
- Water
- A glass or plastic container (e.g. freezer container)

An AC adapter can be bought in your local electronics or diy shop. It's the type you use to recharge your mobile phone. Apart from that nearly every Walkman or PC powered loudspeakers have them (the black power unit with the small plug which is plugged into the loudspeakers etc). Most of these have the power output in mA (milliamperes) and the letters "AC-Adapter" on the back. You can easily find the other items. The cable shoes are just for fixing the cables.

Making the electrolysis bath

1. Fill the container with water up to about half an inch from the top and for every 10-12 ounces of water, add two teaspoons of washing soda or one teaspoon of salt.

2. Cut the small plug off the AC adapter (this is the small plug that normally would be plugged into the loudspeaker, mobile phone, whatever..). You'll see that this part of the cable is made up of two wires. Do not cut any cable leading directly to the part which gets plugged into the power socket on your wall !. Pull the two wires apart and remove about half an inch of the end of the outer coating to lay the wires bare.

3. Attach these wires to the edge of the container using clamps. Make sure that they can't touch each other. Best way is to attach them to opposite sides of the container. Plug the AC-Adapter in. The negative pole electrode should start to give off small bubbles. Unplug the adapter. Mark this wire (the negative electrode) with a piece of coloured sticky tape marked with NEG (for negative).

4. Bend the end of the stainless steel article over and hang it over the edge of the container. The positive electrode (i.e. the other, unmarked wire) should be connected (using a clamp or cable shoe) to the part of the stainless steel article which is under the water. You can e.g. wrap the bare wire around it and hold the wire in place with a clamp.

5. Attach the negative electrode to the coin you want to clean. The best results are achieved when you have about 2 inches of bare wire and wrap this around the coin, fixing it with a clamp.

The electrolysis procedure

When everything is firmly fixed, plug the AC adapter back in. Try not to touch the spoon or coin although if you are using an adapter with 4.5 volts or less, you won't get a shock if everything is working properly. After a moment or so, you should see the coin giving off little bubbles. These are less visible in washing soda than when you use salt. These little bubbles are the electro-chemical reaction which are loosening the dirt from the object facing the anode (the stainless steel object) so you will have to turn the coin round a couple of times. The time depends on the output of your adapter, the number and size of coins etc, so unplug the unit and take the coin out after 15 minutes to check it. Replace it and repeat the procedure as required.
When you check the coin, give it a couple of seconds for the molecules to come to rest, then just rub it between your fingers or give it a brush with an old toothbrush under cold running water. Repeat the process (Electrolysis then a brush) until you are satisfied. You can greatly speed up the process by connecting the wire directly to the coin without using a clamp. Replace the water in the container after a couple of goes. Note that salt is acid and is stronger than washing soda, so it can eat away at coins. Washing soda is an alkali and does no such damage.

Advantages and Disadvantages

In my opinion, electrolysis is by far the best method of cleaning. Having said that, I am not a professional collector. Professionals say that it can be difficult to retain the patina. Coins without a patina are practically worthless and do not look genuine. But on the other hand, coins without their dark patina shine and gleam like the day they were minted, and that is what I like to see when I clean coins. With a little time and trial you can certainly clean your coins using electrolysis without damaging the patina but until you are that far, be prepared to "destroy" a few coins, so do your tests on a few grotty ones first until you've got the hang of it.
Advantages: Quick results, you can clean some coins in about 10 minutes. Low costs - you can go far with 20 dollars and running water.
Disadvantages: Coins that shine like new have little value on the collector market. It needs some practise to remove only the dirt and not the patina.

I hope that this information has helped you. I can not however be held responsible for any damage. Electrolysis is not without it's dangers if the electronic or electrical equipment is not in order. Poor equipment can lead to physical harm.

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