How exactly is this cleaning reaction working?

Question

I am working in the jewelry industry and was wondering how this reaction is working. We frequently clean tarnished silver with a bowl of water lined with aluminum foil, hot water, baking soda, a pinch of salt and a little dishwashing liquid. I have a little chemistry in my background and figure it is an oxidation/reduction reaction. I am curious to exactly what happens and how it is working. Also, are there any other effective methods for cleaning tarnished silver jewelry?

Answer 1

The tarnish is actually Ag2S, Silver Sulphide. The baking soda, salt act as electrolytes and the silver and the aluminium foil act as electrodes. A cell is set up where the Ag+ ions are reduced and Al is oxidised. Thus Ag is cleaned.