How To Clean Bronze Coins. Drown your coin in the mix for a few minutes and wash it with running water. The best way to clean them is mechanically with wooden sticks very well, even if it takes hours, then apply wax on them and keep then in a dry, closed box.
Let the paste dwell on the bronze for half an hour. Spread ketchup all over the coin's. Remove most or all encrustations on the coin so that the original designs and legends are visible again, if they are still there, and always without damaging the patina or the metal, and 2.
If the layer of brown oxidation doesn't budge, return the coins to the dish and let them soak for five more minutes.
When you remove the coins and wipe them with a cloth or paper towel, they should look shiny. Soak gold coins in hot soapy water. Don't put all of your coins in the water at. Antique bronze can become quite dirty or grimy over time.