|MadSci Network: Chemistry|
Dear Craig, Like you, I have had variable experiences with this reaction. Your procedure and materials seem to be correct. The reaction is described as a redox reaction wherein the silver ions in the tarnish (mostly silver sulfide Ag2S) are reduced to silver atoms, while some of the aluminum atoms are oxidized to aluminum ions. The baking soda, sodium bicarbonate, can serve as a mildly basic electrolyte. The easiest way to do the procedure is in an aluminum pan with the silver object in direct contact with the pan, then one does not need the foil. If an aluminum pan is not available, then a glass or ceramic container should be used, and the silver object must be in contact with the aluminum foil under the surface of the solution. I have never tried to use a pan or container made of metal. I always presumed that the metal of the pot would interfere. This is one area where you may have had a problem. There are, however, some unknown (to me at least) factors involved in this process, because I too have had variable results. I have wondered if a piece that is cleaned by this pocess once, might for some reason be difficult to clean a second time. So it looks like you are using the correct materials and process. Could it be that the item you are trying to clean is not silver?
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