Verdigris is a complex insoluble salt of copper hydroxycarbonate. The best way of passivating and removing it is to dissolve it. No severe mechanical tooling required.
The chemistry of choice used by museums for the conservation and display of copper and bronze objects is to use a solution of sodium sesquicarbonate, where the copper in the verdigris is replaced by soluble sodium in solution from the sodium sesquicarbonate. Insoluble copper carbonate precipitates out.
Sodium sesquicarbonate is difficult to buy, because it is semi unstable in air. However, is can be made by mixing the common and reasonably harmless household chemicals of baking soda and washing soda.
Google for instructions on how the mixed solution is prepared and used.
Some museums also preserve their treated coins with Renwax, which seals the surface of the coin, and prevents verdigris from starting again.
Mainly used for ancient bronze coins, where the natural patina can vary greatly in color and darkness.
Edited by sel_69l
04/07/2021 09:28 am