Is Acetone really the trick?

That would be a good experiment. I did a quick lit search and didn't find anything significant on Aluminum reactions with acetone. Usually a very thin layer of aluminum oxide layer that forms on the surface. Al2O3 doesn't really react with much at room temps so as long as you don't have something that's removing this layer, I you should be OK.

I don't have any reason to doubt the credibility of members that posted about the acetone reactions, so that's what makes this interesting. In some ways, I think it's similar to the claims that acetone adversely affects copper (the SUNY Stony Brook paper only shows Cu acetate formation under conditions that wouldn't be used in normal coin conservation). I believe the acetone my be reacting with a secondary material and not the aluminum itself

 

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Hi all. I have purchased a 1964 Kennedy Half Dollar but did not received it yet. But I have a picture of it and seeing this thread, I think that I will need to remove residues from that coin. Could you tell me if I can use acetone or another solvent to clean this coin?

 

Don't use anything on the coin. There is no reason to do that. Your coin is just toned.

 

Wow!!! Thank you very much for the notice. I would really make some clean on the coin if you did not tell me this. But, I guess this coin has DDO on the QUARTER DOLLAR and I don't know if will possible to see without clean it.

 

This 1889 Morgan Dollar is my another new acquisition.
If I clean using acetone is possible the toning on the coin desapear? I don't want it. When I receive that coin on thursday or friday I will need to encapsulate it and, obviously, I will need to clean up the coin. Or don't I need to do it?

 

Yes!! Gracias amigo!!!

 

Looks like normal dirt to me, I have hundreds of these for survival cash, and a lot of them had this dirt or grease on them, I just put them in silver jewelry cleaner on it comes right off. These coins are very plentiful and I would just buy certified with accented hair if you want to collect these.

 

Good advice, Jim. However, a rinse with purified water after the initial acetone bath can have the benefit of removing potentially corrosive inorganic salts which aren't soluble in acetone. These can get on a coin from a number of biological (sweat, spit, etc) and non-biological sources. Then there can be a final rinse with acetone to remove the water.

The above scheme targets both polar and non-polar contaminants.

Cal

 

Thank you Richard. I thought I could not use Silver Jewelry Cleaner on my silver coins.

 

Good scheme to works good the cleaning Cal. Thanks.

 

That would be my guess, also. I'd bet that due to the polarity of acetone (the reason this organic solvent is freely miscible with water), its dissolving a salt of some sort that is either directly reacting with the aluminum, or more likely its reacting slightly with the acetone to form an acetate of some sort.

 

If someone wanted to take the time to research an acetate salt that reacts with aluminum and not with Cu, Ag, Ni, etc., my guess is that would be the culprit.

 

What about finger prints

 

Wow wish i knew this before i got chewed out for thinking differently. I find that to be careless and upseting on the mints part. So the proof sets i still have in original shippers might be a horror story when they are finally opened???? Thought mint packaging was air tight.

 

Acetone does not affect the metal itself on any coin, but I've seen a strange effect on probably a dozen aluminum coins. Mint state aluminum coins come out of the acetone with cloudy white splotches (aluminum oxide is white).

When the coin is wet with the acetone the surfaces look normal, but as the acetone evaporates it leaves behind the white cloudy splotches. You can put the coin back into the acetone and remove it again and change the effect somewhat as it's dependent on the pattern of how the acetone evaporates. You can significantly reduce this effect if you dry the coin rapidly after removing it from the acetone (as with forced air from a fan). If the acetone evaporates simultaneously from the entire face of the coin it hardly does this.

I have no explanation as to what causes it. I've made sure to use clean acetone on aluminum as well to see if it was contaminants from other coins and it didn't make a difference. At this point, I've stopped using acetone on aluminum coins and only use xylene on aluminum.

 

Oh man. Your killing me

 

A good post and good information.

 

You shouldn't, at least not for collectable coins. Silver "dip" will remove toning, but it can also destroy luster and leave the coin looking odd. Silver polish will ruin a coin for collectors.