Wow. I bought some acetone (at last!) tonight. I went at a bag of world coins for about two hours with q-tips. Now, before anyone criticizes me that the method was too harsh - these things were disgusting. They actually smelled. I swear, somebody spilled coffee on them at one point. Add to that the fact that half of them used to be glued to something. And did I mention that every single coin had PVC residue? That being said - there are some fascinating coins in here - nothing newer than WWII. Mostly European. I'll post pictures in another thread when I get the chance. One question - is there anything that can be done for aluminum coinage? About a quarter of the lot was low denomination Nazi aluminum, in desperate need of restoration.
Off topic but check your Pm LOL Also sometimes it is realy necisery to do a bit of a clean up, I have had a few gunked up coins in the past were the option was throw them or clean them I cleaned them (OK I am a Bad Person LOL)
I never had to deal with aluminum coins. US doesn't have any (at least none I'll ever own.) I know aluminum is a tough metal to deal with. Highly reactive and bonds tightly when it oxidizes. That's why it was a valuable metal for so many years (up there with gold or maybe higher.) Hard to extract from its ore. The Washington Monument is capped with a small pyramid of aluminum. Done because the metal was so valuable. And that was in the mid 1880's. Zinc is another nasty metal to deal with. No help in answering your question. But at least I understand your quandry. I'll be interested in the answers you get.
I have some seriously nasty spotty tarnished zinc notgeld coins that came to me in pretty poor condition. It does oxidize steadily and inexorably so I just cleaned them and put them away. I looked around for a way to improve the spotty tarnish but found that the spotting was probably something besides natural tarnish that the zinc might have reacted to. As for cleaning them of gunk and dirt I found the soak in distilled works just as well as with any other type.
As I recall: The coating aluminum gets is generally Al2O3 (aluminum oxide.) VERY tough stuff and VERY hard to deal with short of abrasive action. The good news is that once it's formed it actually seals the aluminum surface and most further problems are avoided. This is good for lawn furniture; it is not good for coins (unless you decide to live with that look.) Zinc does the same thing, oxidize (although I'm not sure the whitish powdery stuff is ZnO. But it's something undesireable.) Problem is that it IS powdery and comes off rather easily. This leaves pitting. Not good. In both cases the best cure is preventative. Put them in something that seals them off from contact with the air. Flips, 2x2's and Airtites are some possibilities.
