Artificial Silver Toning aka Tarnishing Using Anodization
Watch in awe – and you can read more about the anodizing process here.
In this video we show how to use Anodization to give colors to silver coins, also known as toning.
First we mix 200mL of water, 10g of powdered sulfur and 20g of sodium hydroxide and stir for ten minutes or so. This forms a solution of sodium polysulfides.
Then we place in the solution our silver object, in this case a silver coin. We attach the positive terminal of a battery, 1.5 volts is good, to the coin and touch the negative end to solution away from the coin. The silver will get oxidized by the current and form silver sulfide. The layer of silver sulfide imparts color to the coin depending on thickness which is proportional to the time the current is applied.