What is your preferred method of cleaning copper coins?

I have a handful of copper (Roman?) ancient coins, most of which are covered completely in hard verdigris with no details visible whatsoever. They just look smooth because they are encrusted in hard green scale. I had left them soaking in olive oil for the past couple years but that doesn't seem to have done much to loosen anything up. A stiff toothbrush and toothpick still have no effect on the oxidation. I tried an electrolysis method I read about online and that seems to be working very well with my first few test coins. I still can't make out any definite words or dates but I can now see the vague semblance of an emperor's bust. I'll upload a picture for you guys to see, I'm wondering if I should stop here or keep going? I think I want to leave some original patina on, I don't want to strip them to shiny copper. These coins are probably a lost cause but I thought I would see what you all think? And should I coat the cleaned ones in something like wax to protect them?

 

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Would love to see some photos. All my ancients are ones that I have cleaned myself. It is a fun hobby.

 

It was definitely a fun experiment. It is just quite frustrating to be able to see there are definite markings on the coins but not to be able to make sense of anything! I can tell there is lettering but I can't make it out no matter how much I play with lighting and a magnifying loop. If I recall correctly I bought these fairly cheap in a lot on ebay some years ago. I think they were sold as Roman coins but don't remember exactly.

 

Can you see the links to the pictures? They are showing up as red X's for me but when I click it the picture opens up.

 

My preferred method is sodium hydroxide. Search “extreme coin makeover” on coin talk and you’ll see some of my best successes.

 

Thank you I will do that. I used a solution of regular table salt first, then tried again with baking soda which seemed to work faster. I used a 6 volt wall charger and a steel bolt for the cathode.

 

I think he means sodium hydroxide but not electrolysis.

 

I've mostly used water/soap solution and brushing with a brass brush

 

I found that table salt was somewhat aggressive in cleaning; while baking soda was slower and more controlled.


before and after with baking soda

 

I would assume this is with electrolysis

 

I can’t imagine household baking soda in solution would have an effect like this, barring hundreds of hours.

I use straight up household lye, in solution, for up to 9 hours to achieve a result like this

 

this didn't even take an hour with 12v electrolysis and some light scrubbing.

 

Point being WITH ELECTROLYSIS, not with just soaking!

 

I actually have tried soaking copper/bronze coins in baking soda solution and have had it turn green, showing there is some effect.

 

It IS a base, albeit a very light one. I’ve never tried electrolysis. I wonder which is harsher, saturated NaOH, or electrolyzed NaHCO3.

ivd found that hydroxide tends to retain blue and green patina very well, but is harsh to brown and black. No clue why.

just stay away from citric or acetic acid, I made that mistake and destroyed a lovely jade green patina with the acid.

 

preferred method?

don't

 

Sorry for the confusion, but I was directly responding to someone about their electrolysis solution.

 

Yeah, much nicer like this...


Put them in 2x2's?

 

Victor the coin you posted looks great

I've always read bad things about electrolysis such as that it'll destroy patina... was this repatinated or what? Looks good to me