I was reading through an old book about fake US Mint coins the other day, and ran across a little blurb about how the copper planchets for pennies were cleaned in a dilute solution of sulphuric acid and cream of tartar.
Not having sulphuric acid, I tried the cream of tartar (the kind found in the spice rack of your kitchen), and... It works! (Sort of.)
I experimented by putting pennies (old wheats and some from the 70's) in a film canister filled up 1/3 with water, and a small amount of CoT (about what fits on the end of a spoon handle) and let it sit for a day. (It cleaned best on surfaces that were exposed, so for best results, don't try to clean them as a stack...
For the coins from the 70's, where the patina is still "shiny", it stripped off the grime, and kept a glossy appearance. For the wheats (which are a bit corroded), the grime came off, though the surface kept the corroded texture.
Still experimenting, but thought I'd pass it along for some others to give it a try (hopefully on something not too valuable!)
Not having sulphuric acid, I tried the cream of tartar (the kind found in the spice rack of your kitchen), and... It works! (Sort of.)
I experimented by putting pennies (old wheats and some from the 70's) in a film canister filled up 1/3 with water, and a small amount of CoT (about what fits on the end of a spoon handle) and let it sit for a day. (It cleaned best on surfaces that were exposed, so for best results, don't try to clean them as a stack...
For the coins from the 70's, where the patina is still "shiny", it stripped off the grime, and kept a glossy appearance. For the wheats (which are a bit corroded), the grime came off, though the surface kept the corroded texture.
Still experimenting, but thought I'd pass it along for some others to give it a try (hopefully on something not too valuable!)