old 1790,s U.S. coppers

[mike k.]

Anyone know of a safe cleaning method for old coppers found in fields ?

 

[bootyhoundpa]

I usually soak mine in olive oil for several days to loosen the dirt off them... some i find only need a little soap and water...the less cleaning needed the better but i some times find them really cruddy with green verdigris and scale on them...those usually dont clean up well... you mentioned the word safe in your title so beyond soap and water or olive oil you are obviously taking chances... some do the peroxide soak for a few minutes but i dont like the results as is tends to leave a dry look to them...on the ones that i find that are corroded beyond any value and wont come clean with soaking i clean with muriatic acid - this obviously wouldnt be considered safe but ive been able to id some that otherwise would never would have revealed there details...when i clean with acid i just dip an acid brush into acid and lightly brush coin until all the lime build up and verdigris come off then rinse under water ,at this point the coin oxidizes white in color and will reveal any detail that is left ..after rinsing i put them back into the olive oil for a week after which i let them in my basement for a few months till it gets a tarnish on them and then i tumble with other large cents ive found that dont have any detail left on them checking frequently. .the idea being that the high points lighten up and the lower spots remain dark..this can help bring out some contrast..dont over tumble..when optimal results are achieved i pull them out and put a coating of paste wax on them ,let dry and buff with a soft cloth... some people use electrolysis but that will take a very thin layer off and will also leave pitting if the corrosion goes that deep.. if i can id the coin and it has good book value i dont clean them as most cleaning lessens there value... you may want to practice on some worthless wheaties 1st to get an idea of what the results might look like .... just remember they've been in ground for 200 years,chances are it will take more than 5 minutes to clean them...goodluck...