Cleaning a giant copper nugget

[Rincewind]

I have a 125 pound copper nugget a friend found in Michigan. Problem is right now it just looks like a rock. Does anyone know the best way to clean it up? I've heard of using an aqueous ammonium chloride solution but was curious if anyone out there had any ideas. Thanks!

 

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[Casull]

Seems I recall an episode of Cash and Treasures where they used muriatic acid (deck or pool wash) to clean them. Hope that helps.

 

[Michigan Badger]

Like mentionedacid or Liquid Plumber, etc., can be used to break up the natural patina.

Be careful of those nasty fumes! Wear protective equipment and do in outdoors.

The piece will turn a nasty salmon or purplish color.

Wash the entire rock down with baking soda mixed in water to neutralize the acid. Puts lots of it all over and under the nugget brushing it into all pores with a copper bush.

Then you use a copper or brass wire wheel on a drill to buff off the acid residue and expose the copper (wear eye protection).

The final polishing is done with Semichrome paste polish (sold in motorcycle shops and online). Put a buff wheel on your drill and buff and wipe the entire nugget.

Wash the nugget down again with baking soda (really scrub it down good) and rinse with fresh water. When dry wash it down again with denatured alcohol to help dry it out and remove more residue.

Air dry and apply several coats of spray high gloss polyurethane (allowing to dry between coats).

Badger