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Ok, a week ago in science class my science teacher put a penny in some kind of "stuff", took it out, washed it off in plain water, and then the penny was silver.

He put the silver penny in the "stuff" and then held the penny up to a flame for a while and then it turned a bright shiny gold.

What is the stuff he was using? Anyone know?

I want to make a gold penny (It acually looks like real gold, but he said it flakes off if you rub it hard enough.)