Tarnished silver isn’t dirty—it’s silver sulfide, formed when silver reacts with sulfur compounds in the air.
When you put silver + aluminum foil + baking soda + hot water together, you create a simple electrochemical reaction:
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Aluminum is more reactive than silver
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Sulfur “prefers” aluminum over silver
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The sulfur transfers from the silver to the aluminum
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The silver is reduced back to its shiny metallic form
In short:
👉 The tarnish moves from the silver onto the aluminum
That’s why the foil often turns dark while the silver brightens.
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