Electrolytic Cleaning of Ancient Coins

Definition

• An electrolyte is an ionized solution, such as sodium carbonate (washing soda) or sodium bicarbonate (baking soda) in water. Ionization is the process where electrons are added to or removed from atoms, which turns the atoms into ions.

Process

• In the electrolytic cleaning process, the fluid completes an electric circuit between two electrodes. The two electrodes are connected to a source of direct current and one, the cathode, becomes negatively charged while the other, the anode, becomes positively charged. The positive ions in the electrolyte move toward the cathode and the negative ones move toward the anode. This migration of ions is the electric current in that part of the circuit. The current in the external circuit is the migration of ions into the anode, through the wiring and an electric generator, and back to the cathode.

Choice of Electrolyte

• The Kersh Ancient Coins website strongly recommends using sodium carbonate (washing soda) or sodium bicarbonate (baking soda) as electrolytes and carbon or copper conductors as a cathode or anode. Using salt (chlorine) as an electrolyte and stainless steel (chromium) as a cathode or anode gives off dangerous chemicals. Furthermore, using any solution that contains chlorine around coins damages the coin and will promote bronze disease in bronze coins, according to the site.

Method

• Make a simple electrolysis machine with a 9V battery, two copper wires, distilled water and baking soda. First, mix one tablespoon of baking soda in about a pint of water. Connect one copper wire to the positive (+) end of the battery and place the other end in the baking soda solution. Connect the second wire to the negative (-) end of the battery. Wrap the end of the second wire around the coin so that it makes a good connection. The insulation of the wire ends in the solution and around the coin should be stripped back about an inch. Place the coin on the second wire in the solution, not letting it touch the first wire. Coin and wire will begin to bubble and the corrosion will come off in the solution. Remove the coin after a few minutes and clean it gently with a paper towel. Repeat as necessary.

Caution

• Kersch.com rates the harshness of the electrolysis cleaning method at 5 (the highest level) and states that it is not a method for beginners. The method can remove or discolor the patina of the coin. Kersch.com recommends practicing on culls or broken coins to become proficient at the electrolysis method.