I tried a little experiment last night, but it didn't work out so well. I decided to clean some old black looking pennies. Don't worry, these are worthless pennies (well, they are worth 1 cent) but I just wanted to experiment as I've had good success cleaning black silver coins in the past. I used my usual method which is to soak in vinegar+salt for a while, then scrub with baking soda. Well, the result was odd. the penny was indeed clean. It looked like it just came out of the mint. However, the color was off. It didn't look copper anymore. It was very light colored. Sorry I didn't take a photo. But I would have expected it to look like new copper. For example, if I take an old silver coin and clean it, the resulting coin has the same color as a brand new silver coin. But a brand new penny has a much darker copper color than this penny had. Is there a better way to clean a penny to make it look new again, without altering the color?
No. There are some chemicals that can remove light corrosion and there are chemicals that can remove organic material without rubbing ( which can cause scratches, even with baking soda). There are some chemicals that claim to darken copper , but even then a cleaning job with acids is noticeable. So generally they are as they appear.
This sounds gross but it works, take a piece of aluminum foil, bend it in half and here is the gross part, spit on the penny or other corroded copper coins, then gently massage the coin in the saliva between the foil. It will cause a reaction that smells awful but it will tale the corrosion off the coin. Hope this helps!
Experimentally (harshly) cleaning copper basically never ends well and frequently leaves the coins looking odd & discolored. Copper coins are easily ruined & you can never un-clean a copper coin. Soaking in distilled water or Acetone can help remove some surface debris. A chemical like Verdicare can be useful to fight Bronze disease. Whatever you do, you don't want to affect the toning on the surface. I have no further advice to give regarding cleaning copper coins. You just learned the lesson I think.
OK.. I got a picture during lunch.. Sorry it isn't very good, I was in a hurry. The coins on the left and right are the two that I cleaned last night. The bottom is a penny with possibly a little bit of toning, and for comparison the top coin is a brand-new copper bullion coin that is fresh copper from the mint. I have a bunch of these pennies but this particular one on the right was essentially black and you couldn't even hardly make out the date or anything. So, I think it actually looks much better than it did before. But I really wanted it to look new, like it just came from the mint. I was wanting to create some kind of display at home showing the progression of different coins over the years and I wanted the coins to all look new.
Cleaning copper is MUCH more difficult than cleaning silver. For any coin, particularly in MS or near MS state, NEVER, NEVER, NEVER rub the surface with anything. Even though I have seen many people say "It didn't scratch the surface" actually it did. Think about it a minute and you will agree. Now, silver coins may be dipped safely if you know how, but as far as I know, there isn't any dip for copper. Cleaning methods for copper are going to cause scratching or material removal and you will be less happy than when you started, unless you started with a black lump from metal detecting.
If you want the coins to look new, and are not concerned about what you are doing to the value, just wipe the copper well with something like Brasso copper cleaner, wash them well and rinse thoroughly to get off traces of cleaner or soap, and then treat them with VerdiCare to stabilize the surface. They still might tone some, but will be better than when you started.
Those coins you cleaned, that is the color of new copper. The other two coins in your pic, both are toned quite a bit. Copper tones very quickly, and by very quickly I mean days.
That will work I was just addressing the corrosion issue, but you can also buy a can of Nevr-Dull, it's a round silver can full of cotton that has been treated with certain chemicals(it is not toxic to your hands) tear you off a piece large enough for the coin you are cleaning and massage it in the cotton and then dry it with a clean absorbent white cloth and it works really well not that I think you should ever clean a coin.
Not sure if it's the color you're wanting, but yeah, if you leave them exposed out in the open it will. Here's a couple of pics that I did as an experiment some time ago. First pic is right after dipping, second pic is 3 days later.
Agree the two left and right looks cleaned. To me in some cases to the naked eye a cleaned coin, what you say looks like it came from the mint, with wear is pretty obvious. I wish you took before an after pictures on that IHC.
